All EyeLink clinical and oculomotor research publications are listed below in alphabetical order based on the first author. You can search the publications using key words such as Saccadic Adaptation, Schizophrenia, Nystagmus, etc. You can also search for individual author names. If we missed any EyeLink clinical or oculomotor article, please email us!
David Aagten-Murphy; Paul M Bays Automatic and intentional influences on saccade landing Journal Article Journal of Neurophysiology, 118 , pp. 1105–1122, 2017. @article{Aagten-Murphy2017, title = {Automatic and intentional influences on saccade landing}, author = {David Aagten-Murphy and Paul M Bays}, doi = {10.1152/jn.00141.2017}, year = {2017}, date = {2017-01-01}, journal = {Journal of Neurophysiology}, volume = {118}, pages = {1105--1122}, abstract = {Saccadic eye movements enable us to rapidly direct our high-resolution fovea onto relevant parts of the visual world. However, while we can intentionally select a location as a saccade target, the wider visual scene also influences our executed movements. In the presence of multiple objects, eye movements may be “captured” to the location of a distractor object, or be biased toward the intermediate position between objects (the “global effect”). Here we examined how the relative strengths of the global effect and visual object capture changed with saccade latency, the separation between visual items and stimulus contrast. Importantly, while many previous studies have omitted giving observers explicit instructions, we instructed participants to either saccade to a specified target object or to the midpoint between two stimuli. This allowed us to examine how their explicit movement goal influenced the likelihood that their saccades terminated at either the target, distractor, or intermediate locations. Using a probabilistic mixture model, we found evidence that both visual object capture and the global effect co-occurred at short latencies and declined as latency increased. As object separation increased, capture came to dominate the landing positions of fast saccades, with reduced global effect. Using the mixture model fits, we dissociated the proportion of unavoidably captured saccades to each location from those intentionally directed to the task goal. From this we could extract the time course of competition between automatic capture and intentional targeting. We show that task instructions substantially altered the distribution of saccade landing points, even at the shortest latencies. NEW & NOTEWORTHY When making an eye movement to a target location, the presence of a nearby distractor can cause the saccade to unintentionally terminate at the distractor itself or the average position in between stimuli. With probabilistic mixture models, we quantified how both unavoidable capture and goal-di rected targeting were influenced by changing the task and the target-distractor separation. Using this novel technique, we could extract the time course over which automatic and intentional processes compete for control of saccades.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Saccadic eye movements enable us to rapidly direct our high-resolution fovea onto relevant parts of the visual world. However, while we can intentionally select a location as a saccade target, the wider visual scene also influences our executed movements. In the presence of multiple objects, eye movements may be “captured” to the location of a distractor object, or be biased toward the intermediate position between objects (the “global effect”). Here we examined how the relative strengths of the global effect and visual object capture changed with saccade latency, the separation between visual items and stimulus contrast. Importantly, while many previous studies have omitted giving observers explicit instructions, we instructed participants to either saccade to a specified target object or to the midpoint between two stimuli. This allowed us to examine how their explicit movement goal influenced the likelihood that their saccades terminated at either the target, distractor, or intermediate locations. Using a probabilistic mixture model, we found evidence that both visual object capture and the global effect co-occurred at short latencies and declined as latency increased. As object separation increased, capture came to dominate the landing positions of fast saccades, with reduced global effect. Using the mixture model fits, we dissociated the proportion of unavoidably captured saccades to each location from those intentionally directed to the task goal. From this we could extract the time course of competition between automatic capture and intentional targeting. We show that task instructions substantially altered the distribution of saccade landing points, even at the shortest latencies. NEW & NOTEWORTHY When making an eye movement to a target location, the presence of a nearby distractor can cause the saccade to unintentionally terminate at the distractor itself or the average position in between stimuli. With probabilistic mixture models, we quantified how both unavoidable capture and goal-di rected targeting were influenced by changing the task and the target-distractor separation. Using this novel technique, we could extract the time course over which automatic and intentional processes compete for control of saccades. |
Mathias Abegg; Dario Pianezzi; Jason J S Barton A vertical asymmetry in saccades Journal Article Journal of Eye Movement Research, 8 (5), pp. 1–10, 2015. @article{Abegg2015, title = {A vertical asymmetry in saccades}, author = {Mathias Abegg and Dario Pianezzi and Jason J S Barton}, doi = {10.16910/jemr.8.5.3}, year = {2015}, date = {2015-01-01}, journal = {Journal of Eye Movement Research}, volume = {8}, number = {5}, pages = {1--10}, abstract = {Visual exploration of natural scenes imposes demands that differ between the upper and the lower visual hemifield. Yet little is known about how ocular motor performance is affected by the location of visual stimuli or the direction of a behavioural response. We compared saccadic latencies between upper and lower hemifield in a variety of conditions, including short-latency prosaccades, long-latency prosaccades, antisaccades, memory-guided saccades and saccades with increased attentional and selection demand. All saccade types, except memory guided saccades, had shorter latencies when saccades were directed towards the upper field as compared to downward saccades (ptextless0.05). This upper field reaction time advantage probably arises in ocular motor rather than visual processing. It may originate in structures involved in motor preparation rather than execution.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Visual exploration of natural scenes imposes demands that differ between the upper and the lower visual hemifield. Yet little is known about how ocular motor performance is affected by the location of visual stimuli or the direction of a behavioural response. We compared saccadic latencies between upper and lower hemifield in a variety of conditions, including short-latency prosaccades, long-latency prosaccades, antisaccades, memory-guided saccades and saccades with increased attentional and selection demand. All saccade types, except memory guided saccades, had shorter latencies when saccades were directed towards the upper field as compared to downward saccades (ptextless0.05). This upper field reaction time advantage probably arises in ocular motor rather than visual processing. It may originate in structures involved in motor preparation rather than execution. |
Larry Allen Abel; Zhong I Wang; Louis F Dell'Osso Wavelet analysis in infantile nystagmus syndrome: Limitations and abilities Journal Article Investigative Ophthalmology & Visual Science, 49 (8), pp. 3413–3423, 2008. @article{Abel2008, title = {Wavelet analysis in infantile nystagmus syndrome: Limitations and abilities}, author = {Larry Allen Abel and Zhong I Wang and Louis F Dell'Osso}, doi = {10.1167/iovs.08-1710}, year = {2008}, date = {2008-01-01}, journal = {Investigative Ophthalmology & Visual Science}, volume = {49}, number = {8}, pages = {3413--3423}, abstract = {PURPOSE: To investigate the proper usage of wavelet analysis in infantile nystagmus syndrome (INS) and determine its limitations and abilities. METHODS: Data were analyzed from accurate eye-movement recordings of INS patients. Wavelet analysis was performed to examine the foveation characteristics, morphologic characteristics and time variation in different INS waveforms. Also compared were the wavelet analysis and the expanded nystagmus acuity function (NAFX) analysis on sections of pre- and post-tenotomy data. RESULTS: Wavelet spectra showed some sensitivity to different features of INS waveforms and reflected their variations across time. However, wavelet analysis was not effective in detecting foveation periods, especially in a complicated INS waveform. NAFX, on the other hand, was a much more direct way of evaluating waveform changes after nystagmus treatments. CONCLUSIONS: Wavelet analysis is a tool that performs, with difficulty, some things that can be done faster and better by directly operating on the nystagmus waveform itself. It appears, however, to be insensitive to the subtle but visually important improvements brought about by INS therapies. Wavelet analysis may have a role in developing automated waveform classifiers where its time-dependent characterization of the waveform can be used. The limitations of wavelet analysis outweighed its abilities in INS waveform-characteristic examination.}, keywords = {}, pubstate = {published}, tppubtype = {article} } PURPOSE: To investigate the proper usage of wavelet analysis in infantile nystagmus syndrome (INS) and determine its limitations and abilities. METHODS: Data were analyzed from accurate eye-movement recordings of INS patients. Wavelet analysis was performed to examine the foveation characteristics, morphologic characteristics and time variation in different INS waveforms. Also compared were the wavelet analysis and the expanded nystagmus acuity function (NAFX) analysis on sections of pre- and post-tenotomy data. RESULTS: Wavelet spectra showed some sensitivity to different features of INS waveforms and reflected their variations across time. However, wavelet analysis was not effective in detecting foveation periods, especially in a complicated INS waveform. NAFX, on the other hand, was a much more direct way of evaluating waveform changes after nystagmus treatments. CONCLUSIONS: Wavelet analysis is a tool that performs, with difficulty, some things that can be done faster and better by directly operating on the nystagmus waveform itself. It appears, however, to be insensitive to the subtle but visually important improvements brought about by INS therapies. Wavelet analysis may have a role in developing automated waveform classifiers where its time-dependent characterization of the waveform can be used. The limitations of wavelet analysis outweighed its abilities in INS waveform-characteristic examination. |
Irene Ablinger; Walter Huber; Kerstin I Schattka; Ralph Radach Recovery in a letter-by-letter reader: More efficiency at the expense of normal reading strategy Journal Article Neurocase, 19 (3), pp. 236–255, 2013. @article{Ablinger2013, title = {Recovery in a letter-by-letter reader: More efficiency at the expense of normal reading strategy}, author = {Irene Ablinger and Walter Huber and Kerstin I Schattka and Ralph Radach}, doi = {10.1080/13554794.2012.667119}, year = {2013}, date = {2013-01-01}, journal = {Neurocase}, volume = {19}, number = {3}, pages = {236--255}, abstract = {Although changes in reading performance of recovering letter-by-letter readers have been described in some detail, no prior research has provided an in-depth analysis of the underlying adaptive word processing strategies. Our work examined the reading performance of a letter-by-letter reader, FH, over a period of 15 months, using eye movement methodology to delineate the recovery process at two different time points (T1, T2). A central question is whether recovery is characterized either by moving back towards normal word processing or by refinement and possibly automatization of an existing pathological strategy that was developed in response to the impairment. More specifically, we hypothesized that letter-by-letter reading may be executed with at least four different strategies and our work sought to distinguish between these alternatives. During recovery significant improvements in reading performance were achieved. A shift of fixation positions from the far left to the extreme right of target words was combined with many small and very few longer regressive saccades. Apparently, ‘letter-by-letter reading' took the form of local clustering, most likely corresponding to the formation ofsublexical units ofanalysis. This pattern was more pronounced at T2, suggesting that improvements in reading efficiency may come at the expense of making it harder to eventually return to normal reading.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Although changes in reading performance of recovering letter-by-letter readers have been described in some detail, no prior research has provided an in-depth analysis of the underlying adaptive word processing strategies. Our work examined the reading performance of a letter-by-letter reader, FH, over a period of 15 months, using eye movement methodology to delineate the recovery process at two different time points (T1, T2). A central question is whether recovery is characterized either by moving back towards normal word processing or by refinement and possibly automatization of an existing pathological strategy that was developed in response to the impairment. More specifically, we hypothesized that letter-by-letter reading may be executed with at least four different strategies and our work sought to distinguish between these alternatives. During recovery significant improvements in reading performance were achieved. A shift of fixation positions from the far left to the extreme right of target words was combined with many small and very few longer regressive saccades. Apparently, ‘letter-by-letter reading' took the form of local clustering, most likely corresponding to the formation ofsublexical units ofanalysis. This pattern was more pronounced at T2, suggesting that improvements in reading efficiency may come at the expense of making it harder to eventually return to normal reading. |
Irene Ablinger; Kerstin Von Heyden; Christian Vorstius; Katja Halm; Walter Huber; Ralph Radach An eye movement based reading intervention in lexical and segmental readers with acquired dyslexia Journal Article Neuropsychological Rehabilitation, 24 (6), pp. 833–867, 2014. @article{Ablinger2014a, title = {An eye movement based reading intervention in lexical and segmental readers with acquired dyslexia}, author = {Irene Ablinger and Kerstin {Von Heyden} and Christian Vorstius and Katja Halm and Walter Huber and Ralph Radach}, doi = {10.1080/09602011.2014.913530}, year = {2014}, date = {2014-01-01}, journal = {Neuropsychological Rehabilitation}, volume = {24}, number = {6}, pages = {833--867}, abstract = {Due to their brain damage, aphasic patients with acquired dyslexia often rely to a greater extent on lexical or segmental reading procedures. Thus, therapy intervention is mostly targeted on the more impaired reading strategy. In the present work we introduce a novel therapy approach based on real-time measurement of patients' eye movements as they attempt to read words. More specifically, an eye movement contingent technique of stepwise letter de-masking was used to support sequential reading, whereas fixation-dependent initial masking of non-central letters stimulated a lexical (parallel) reading strategy. Four lexical and four segmental readers with acquired central dyslexia received our intensive reading intervention. All participants showed remarkable improvements as evident in reduced total reading time, a reduced number of fixations per word and improved reading accuracy. Both types of intervention led to item-specific training effects in all subjects. A generalisation to untrained items was only found in segmental readers after the lexical training. Eye movement analyses were also used to compare word processing before and after therapy, indicating that all patients, with one exclusion, maintained their preferred reading strategy. However, in several cases the balance between sequential and lexical processing became less extreme, indicating a more effective individual interplay of both word processing routes.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Due to their brain damage, aphasic patients with acquired dyslexia often rely to a greater extent on lexical or segmental reading procedures. Thus, therapy intervention is mostly targeted on the more impaired reading strategy. In the present work we introduce a novel therapy approach based on real-time measurement of patients' eye movements as they attempt to read words. More specifically, an eye movement contingent technique of stepwise letter de-masking was used to support sequential reading, whereas fixation-dependent initial masking of non-central letters stimulated a lexical (parallel) reading strategy. Four lexical and four segmental readers with acquired central dyslexia received our intensive reading intervention. All participants showed remarkable improvements as evident in reduced total reading time, a reduced number of fixations per word and improved reading accuracy. Both types of intervention led to item-specific training effects in all subjects. A generalisation to untrained items was only found in segmental readers after the lexical training. Eye movement analyses were also used to compare word processing before and after therapy, indicating that all patients, with one exclusion, maintained their preferred reading strategy. However, in several cases the balance between sequential and lexical processing became less extreme, indicating a more effective individual interplay of both word processing routes. |
Irene Ablinger; Ralph Radach Diverging receptive and expressive word processing mechanisms in a deep dyslexic reader Journal Article Neuropsychologia, 81 , pp. 12–21, 2016. @article{Ablinger2016, title = {Diverging receptive and expressive word processing mechanisms in a deep dyslexic reader}, author = {Irene Ablinger and Ralph Radach}, doi = {10.1016/j.neuropsychologia.2015.11.023}, year = {2016}, date = {2016-01-01}, journal = {Neuropsychologia}, volume = {81}, pages = {12--21}, publisher = {Elsevier}, abstract = {We report on KJ, a patient with acquired dyslexia due to cerebral artery infarction. He represents an unusually clear case of an "output" deep dyslexic reader, with a distinct pattern of pure semantic reading. According to current neuropsychological models of reading, the severity of this condition is directly related to the degree of impairment in semantic and phonological representations and the resulting imbalance in the interaction between the two word processing pathways. The present work sought to examine whether an innovative eye movement supported intervention combining lexical and segmental therapy would strengthen phonological processing and lead to an attenuation of the extreme semantic over-involvement in KJ's word identification process. Reading performance was assessed before (T1) between (T2) and after (T3) therapy using both analyses of linguistic errors and word viewing patterns. Therapy resulted in improved reading aloud accuracy along with a change in error distribution that suggested a return to more sequential reading. Interestingly, this was in contrast to the dynamics of moment-to-moment word processing, as eye movement analyses still suggested a predominantly holistic strategy, even at T3. So, in addition to documenting the success of the therapeutic intervention, our results call for a theoretically important conclusion: Real-time letter and word recognition routines should be considered separately from properties of the verbal output. Combining both perspectives may provide a promising strategy for future assessment and therapy evaluation.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We report on KJ, a patient with acquired dyslexia due to cerebral artery infarction. He represents an unusually clear case of an "output" deep dyslexic reader, with a distinct pattern of pure semantic reading. According to current neuropsychological models of reading, the severity of this condition is directly related to the degree of impairment in semantic and phonological representations and the resulting imbalance in the interaction between the two word processing pathways. The present work sought to examine whether an innovative eye movement supported intervention combining lexical and segmental therapy would strengthen phonological processing and lead to an attenuation of the extreme semantic over-involvement in KJ's word identification process. Reading performance was assessed before (T1) between (T2) and after (T3) therapy using both analyses of linguistic errors and word viewing patterns. Therapy resulted in improved reading aloud accuracy along with a change in error distribution that suggested a return to more sequential reading. Interestingly, this was in contrast to the dynamics of moment-to-moment word processing, as eye movement analyses still suggested a predominantly holistic strategy, even at T3. So, in addition to documenting the success of the therapeutic intervention, our results call for a theoretically important conclusion: Real-time letter and word recognition routines should be considered separately from properties of the verbal output. Combining both perspectives may provide a promising strategy for future assessment and therapy evaluation. |
Leah Acker; Erica N Pino; Edward S Boyden; Robert Desimone FEF inactivation with improved optogenetic methods Journal Article Proceedings of the National Academy of Sciences, 113 (46), pp. E7297–E7306, 2016. @article{Acker2016, title = {FEF inactivation with improved optogenetic methods}, author = {Leah Acker and Erica N Pino and Edward S Boyden and Robert Desimone}, doi = {10.1073/pnas.1610784113}, year = {2016}, date = {2016-01-01}, journal = {Proceedings of the National Academy of Sciences}, volume = {113}, number = {46}, pages = {E7297--E7306}, abstract = {Optogenetic methods have been highly effective for suppressing neural activity and modulating behavior in rodents, but effects have been much smaller in primates, which have much larger brains. Here, we present a suite of technologies to use optogenetics effectively in primates and apply these tools to a classic question in oculomotor control. First, we measured light absorption and heat propagation in vivo, optimized the conditions for using the red-light-shifted halorhodopsin Jaws in primates, and developed a large-volume illuminator to maximize light delivery with minimal heating and tissue displacement. Together, these advances allowed for nearly universal neuronal inactivation across more than 10 mm(3) of the cortex. Using these tools, we demonstrated large behavioral changes (i.e., up to several fold increases in error rate) with relatively low light power densities (≤100 mW/mm(2)) in the frontal eye field (FEF). Pharmacological inactivation studies have shown that the FEF is critical for executing saccades to remembered locations. FEF neurons increase their firing rate during the three epochs of the memory-guided saccade task: visual stimulus presentation, the delay interval, and motor preparation. It is unclear from earlier work, however, whether FEF activity during each epoch is necessary for memory-guided saccade execution. By harnessing the temporal specificity of optogenetics, we found that FEF contributes to memory-guided eye movements during every epoch of the memory-guided saccade task (the visual, delay, and motor periods).}, keywords = {}, pubstate = {published}, tppubtype = {article} } Optogenetic methods have been highly effective for suppressing neural activity and modulating behavior in rodents, but effects have been much smaller in primates, which have much larger brains. Here, we present a suite of technologies to use optogenetics effectively in primates and apply these tools to a classic question in oculomotor control. First, we measured light absorption and heat propagation in vivo, optimized the conditions for using the red-light-shifted halorhodopsin Jaws in primates, and developed a large-volume illuminator to maximize light delivery with minimal heating and tissue displacement. Together, these advances allowed for nearly universal neuronal inactivation across more than 10 mm(3) of the cortex. Using these tools, we demonstrated large behavioral changes (i.e., up to several fold increases in error rate) with relatively low light power densities (≤100 mW/mm(2)) in the frontal eye field (FEF). Pharmacological inactivation studies have shown that the FEF is critical for executing saccades to remembered locations. FEF neurons increase their firing rate during the three epochs of the memory-guided saccade task: visual stimulus presentation, the delay interval, and motor preparation. It is unclear from earlier work, however, whether FEF activity during each epoch is necessary for memory-guided saccade execution. By harnessing the temporal specificity of optogenetics, we found that FEF contributes to memory-guided eye movements during every epoch of the memory-guided saccade task (the visual, delay, and motor periods). |
John F Ackermann; Michael S Landy Choice of saccade endpoint under risk Journal Article Journal of Vision, 13 (3), pp. 1–20, 2013. @article{Ackermann2013, title = {Choice of saccade endpoint under risk}, author = {John F Ackermann and Michael S Landy}, doi = {10.1167/13.3.27}, year = {2013}, date = {2013-01-01}, journal = {Journal of Vision}, volume = {13}, number = {3}, pages = {1--20}, abstract = {Eye movements function to bring detailed information onto the high-resolution region of the retina. Previous research has shown that human observers select fixation points that maximize information acquisition and minimize target location uncertainty. In this study, we ask whether human observers choose the saccade endpoint that maximizes gain when there are explicit rewards associated with correctly detecting the target. Observers performed an 8-alternative forced-choice detection task for a contrast-defined target in noise. After a single saccade, observers indicated the target location. Each potential target location had an associated reward that was known to the observer. In some conditions, the reward at one location was higher than at the other locations. We compared human saccade endpoints to those of an ideal observer that maximizes expected gain given the respective human observer's visibility map, i.e., d' for target detection as a function of retinal location. Varying the location of the highest reward had a significant effect on human observers' distribution of saccade endpoints. Both human and ideal observers show a high density of saccades made toward the highest rewarded and actual target locations. But humans' overall spatial distributions of saccade endpoints differed significantly from the ideal observer as they made a greater number of saccade to locations far from the highest rewarded and actual target locations. Suboptimal choice of saccade endpoint, possibly in combination with suboptimal integration of information across saccades, had a significant effect on human observers' ability to correctly detect the target and maximize gain.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Eye movements function to bring detailed information onto the high-resolution region of the retina. Previous research has shown that human observers select fixation points that maximize information acquisition and minimize target location uncertainty. In this study, we ask whether human observers choose the saccade endpoint that maximizes gain when there are explicit rewards associated with correctly detecting the target. Observers performed an 8-alternative forced-choice detection task for a contrast-defined target in noise. After a single saccade, observers indicated the target location. Each potential target location had an associated reward that was known to the observer. In some conditions, the reward at one location was higher than at the other locations. We compared human saccade endpoints to those of an ideal observer that maximizes expected gain given the respective human observer's visibility map, i.e., d' for target detection as a function of retinal location. Varying the location of the highest reward had a significant effect on human observers' distribution of saccade endpoints. Both human and ideal observers show a high density of saccades made toward the highest rewarded and actual target locations. But humans' overall spatial distributions of saccade endpoints differed significantly from the ideal observer as they made a greater number of saccade to locations far from the highest rewarded and actual target locations. Suboptimal choice of saccade endpoint, possibly in combination with suboptimal integration of information across saccades, had a significant effect on human observers' ability to correctly detect the target and maximize gain. |
Robert Adam; Alexander Leff; Nihal Sinha; Christopher Turner; Paul Bays; Bogdan Draganski; Masud Husain Dopamine reverses reward insensitivity in apathy following globus pallidus lesions Journal Article Cortex, 49 (5), pp. 1292–1303, 2013. @article{Adam2013, title = {Dopamine reverses reward insensitivity in apathy following globus pallidus lesions}, author = {Robert Adam and Alexander Leff and Nihal Sinha and Christopher Turner and Paul Bays and Bogdan Draganski and Masud Husain}, doi = {10.1016/j.cortex.2012.04.013}, year = {2013}, date = {2013-01-01}, journal = {Cortex}, volume = {49}, number = {5}, pages = {1292--1303}, publisher = {Elsevier Ltd}, abstract = {Apathy is a complex, behavioural disorder associated with reduced spontaneous initiation of actions. Although present in mild forms in some healthy people, it is a pathological state in conditions such as Alzheimer's and Parkinson's disease where it can have profoundly devastating effects. Understanding the mechanisms underlying apathy is therefore of urgent concern but this has proven difficult because widespread brain changes in neurodegenerative diseases make interpretation difficult and there is no good animal model.Here we present a very rare case with profound apathy following bilateral, focal lesions of the basal ganglia, with globus pallidus regions that connect with orbitofrontal (OFC) and ventromedial prefrontal cortex (VMPFC) particularly affected. Using two measures of oculomotor decision-making we show that apathy in this individual was associated with reward insensitivity. However, reward sensitivity could be established partially with levodopa and more effectively with a dopamine receptor agonist. Concomitantly, there was an improvement in the patient's clinical state, with reduced apathy, greater motivation and increased social interactions. These findings provide a model system to study a key neuropsychiatric disorder. They demonstrate that reward insensitivity associated with basal ganglia dysfunction might be an important component of apathy that can be reversed by dopaminergic modulation.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Apathy is a complex, behavioural disorder associated with reduced spontaneous initiation of actions. Although present in mild forms in some healthy people, it is a pathological state in conditions such as Alzheimer's and Parkinson's disease where it can have profoundly devastating effects. Understanding the mechanisms underlying apathy is therefore of urgent concern but this has proven difficult because widespread brain changes in neurodegenerative diseases make interpretation difficult and there is no good animal model.Here we present a very rare case with profound apathy following bilateral, focal lesions of the basal ganglia, with globus pallidus regions that connect with orbitofrontal (OFC) and ventromedial prefrontal cortex (VMPFC) particularly affected. Using two measures of oculomotor decision-making we show that apathy in this individual was associated with reward insensitivity. However, reward sensitivity could be established partially with levodopa and more effectively with a dopamine receptor agonist. Concomitantly, there was an improvement in the patient's clinical state, with reduced apathy, greater motivation and increased social interactions. These findings provide a model system to study a key neuropsychiatric disorder. They demonstrate that reward insensitivity associated with basal ganglia dysfunction might be an important component of apathy that can be reversed by dopaminergic modulation. |
Rick A Adams; Eduardo Aponte; Louise Marshall; Karl J Friston Active inference and oculomotor pursuit: The dynamic causal modelling of eye movements Journal Article Journal of Neuroscience Methods, 242 , pp. 1–14, 2015. @article{Adams2015, title = {Active inference and oculomotor pursuit: The dynamic causal modelling of eye movements}, author = {Rick A Adams and Eduardo Aponte and Louise Marshall and Karl J Friston}, doi = {10.1016/j.jneumeth.2015.01.003}, year = {2015}, date = {2015-01-01}, journal = {Journal of Neuroscience Methods}, volume = {242}, pages = {1--14}, publisher = {Elsevier B.V.}, abstract = {Background: This paper introduces a new paradigm that allows one to quantify the Bayesian beliefs evidenced by subjects during oculomotor pursuit. Subjects' eye tracking responses to a partially occluded sinusoidal target were recorded non-invasively and averaged. These response averages were then analysed using dynamic causal modelling (DCM). In DCM, observed responses are modelled using biologically plausible generative or forward models - usually biophysical models of neuronal activity. New method: Our key innovation is to use a generative model based on a normative (Bayes-optimal) model of active inference to model oculomotor pursuit in terms of subjects' beliefs about how visual targets move and how their oculomotor system responds. Our aim here is to establish the face validity of the approach, by manipulating the content and precision of sensory information - and examining the ensuing changes in the subjects' implicit beliefs. These beliefs are inferred from their eye movements using the normative model. Results: We show that on average, subjects respond to an increase in the 'noise' of target motion by increasing sensory precision in their models of the target trajectory. In other words, they attend more to the sensory attributes of a noisier stimulus. Conversely, subjects only change kinetic parameters in their model but not precision, in response to increased target speed. Conclusions: Using this technique one can estimate the precisions of subjects' hierarchical Bayesian beliefs about target motion. We hope to apply this paradigm to subjects with schizophrenia, whose pursuit abnormalities may result from the abnormal encoding of precision.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Background: This paper introduces a new paradigm that allows one to quantify the Bayesian beliefs evidenced by subjects during oculomotor pursuit. Subjects' eye tracking responses to a partially occluded sinusoidal target were recorded non-invasively and averaged. These response averages were then analysed using dynamic causal modelling (DCM). In DCM, observed responses are modelled using biologically plausible generative or forward models - usually biophysical models of neuronal activity. New method: Our key innovation is to use a generative model based on a normative (Bayes-optimal) model of active inference to model oculomotor pursuit in terms of subjects' beliefs about how visual targets move and how their oculomotor system responds. Our aim here is to establish the face validity of the approach, by manipulating the content and precision of sensory information - and examining the ensuing changes in the subjects' implicit beliefs. These beliefs are inferred from their eye movements using the normative model. Results: We show that on average, subjects respond to an increase in the 'noise' of target motion by increasing sensory precision in their models of the target trajectory. In other words, they attend more to the sensory attributes of a noisier stimulus. Conversely, subjects only change kinetic parameters in their model but not precision, in response to increased target speed. Conclusions: Using this technique one can estimate the precisions of subjects' hierarchical Bayesian beliefs about target motion. We hope to apply this paradigm to subjects with schizophrenia, whose pursuit abnormalities may result from the abnormal encoding of precision. |
Rick A Adams; Markus Bauer; Dimitris Pinotsis; Karl J Friston Dynamic causal modelling of eye movements during pursuit: Confirming precision-encoding in V1 using MEG Journal Article Neuroimage, 132 , pp. 175–189, 2016. @article{Adams2016, title = {Dynamic causal modelling of eye movements during pursuit: Confirming precision-encoding in V1 using MEG}, author = {Rick A Adams and Markus Bauer and Dimitris Pinotsis and Karl J Friston}, doi = {10.1016/j.neuroimage.2016.02.055}, year = {2016}, date = {2016-01-01}, journal = {Neuroimage}, volume = {132}, pages = {175--189}, publisher = {The Authors}, abstract = {This paper shows that it is possible to estimate the subjective precision (inverse variance) of Bayesian beliefs during oculomotor pursuit. Subjects viewed a sinusoidal target, with or without random fluctuations in its motion. Eye trajectories and magnetoencephalographic (MEG) data were recorded concurrently. The target was periodically occluded, such that its reappearance caused a visual evoked response field (ERF). Dynamic causal modelling (DCM) was used to fit models of eye trajectories and the ERFs. The DCM for pursuit was based on predictive coding and active inference, and predicts subjects' eye movements based on their (subjective) Bayesian beliefs about target (and eye) motion. The precisions of these hierarchical beliefs can be inferred from behavioural (pursuit) data. The DCM for MEG data used an established biophysical model of neuronal activity that includes parameters for the gain of superficial pyramidal cells, which is thought to encode precision at the neuronal level. Previous studies (using DCM of pursuit data) suggest that noisy target motion increases subjective precision at the sensory level: i.e., subjects attend more to the target's sensory attributes. We compared (noisy motion-induced) changes in the synaptic gain based on the modelling of MEG data to changes in subjective precision estimated using the pursuit data. We demonstrate that imprecise target motion increases the gain of superficial pyramidal cells in V1 (across subjects). Furthermore, increases in sensory precision – inferred by our behavioural DCM – correlate with the increase in gain in V1, across subjects. This is a step towards a fully integrated model of brain computations, cortical responses and behaviour that may provide a useful clinical tool in conditions like schizophrenia.}, keywords = {}, pubstate = {published}, tppubtype = {article} } This paper shows that it is possible to estimate the subjective precision (inverse variance) of Bayesian beliefs during oculomotor pursuit. Subjects viewed a sinusoidal target, with or without random fluctuations in its motion. Eye trajectories and magnetoencephalographic (MEG) data were recorded concurrently. The target was periodically occluded, such that its reappearance caused a visual evoked response field (ERF). Dynamic causal modelling (DCM) was used to fit models of eye trajectories and the ERFs. The DCM for pursuit was based on predictive coding and active inference, and predicts subjects' eye movements based on their (subjective) Bayesian beliefs about target (and eye) motion. The precisions of these hierarchical beliefs can be inferred from behavioural (pursuit) data. The DCM for MEG data used an established biophysical model of neuronal activity that includes parameters for the gain of superficial pyramidal cells, which is thought to encode precision at the neuronal level. Previous studies (using DCM of pursuit data) suggest that noisy target motion increases subjective precision at the sensory level: i.e., subjects attend more to the target's sensory attributes. We compared (noisy motion-induced) changes in the synaptic gain based on the modelling of MEG data to changes in subjective precision estimated using the pursuit data. We demonstrate that imprecise target motion increases the gain of superficial pyramidal cells in V1 (across subjects). Furthermore, increases in sensory precision – inferred by our behavioural DCM – correlate with the increase in gain in V1, across subjects. This is a step towards a fully integrated model of brain computations, cortical responses and behaviour that may provide a useful clinical tool in conditions like schizophrenia. |
Mehmet N Ağaoğlu; Haluk Öğmen; Susana T L Chung Unmasking saccadic uncrowding Journal Article Vision Research, 127 , pp. 152–164, 2016. @article{Agaoglu2016b, title = {Unmasking saccadic uncrowding}, author = {Mehmet N Ağaoğlu and Haluk Öğmen and Susana T L Chung}, doi = {10.1016/j.visres.2016.08.003}, year = {2016}, date = {2016-01-01}, journal = {Vision Research}, volume = {127}, pages = {152--164}, abstract = {Stimuli that are briefly presented around the time of saccades are often perceived with spatiotemporal distortions. These distortions do not always have deleterious effects on the visibility and identification of a stimulus. Recent studies reported that when a stimulus is the target of an intended saccade, it is released from both masking and crowding. Here, we investigated pre-saccadic changes in single and crowded letter recognition performance in the absence (Experiment 1) and the presence (Experiment 2) of backward masks to determine the extent to which saccadic “uncrowding” and “unmasking” mechanisms are similar. Our results show that pre-saccadic improvements in letter recognition performance are mostly due to the presence of masks and/or stimulus transients which occur after the target is presented. More importantly, we did not find any decrease in crowding strength before impending saccades. A simplified version of a dual-channel neural model, originally proposed to explain masking phenomena, with several saccadic add-on mechanisms, could account for our results in Experiment 1. However, this model falls short in explaining how saccades drastically reduced the effect of backward masking (Experiment 2). The addition of a remapping mechanism that alters the relative spatial positions of stimuli was needed to fully account for the improvements observed when backward masks followed the letter stimuli. Taken together, our results (i) are inconsistent with saccadic uncrowding, (ii) strongly support saccadic unmasking, and (iii) suggest that pre-saccadic letter recognition is modulated by multiple perisaccadic mechanisms with different time courses.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Stimuli that are briefly presented around the time of saccades are often perceived with spatiotemporal distortions. These distortions do not always have deleterious effects on the visibility and identification of a stimulus. Recent studies reported that when a stimulus is the target of an intended saccade, it is released from both masking and crowding. Here, we investigated pre-saccadic changes in single and crowded letter recognition performance in the absence (Experiment 1) and the presence (Experiment 2) of backward masks to determine the extent to which saccadic “uncrowding” and “unmasking” mechanisms are similar. Our results show that pre-saccadic improvements in letter recognition performance are mostly due to the presence of masks and/or stimulus transients which occur after the target is presented. More importantly, we did not find any decrease in crowding strength before impending saccades. A simplified version of a dual-channel neural model, originally proposed to explain masking phenomena, with several saccadic add-on mechanisms, could account for our results in Experiment 1. However, this model falls short in explaining how saccades drastically reduced the effect of backward masking (Experiment 2). The addition of a remapping mechanism that alters the relative spatial positions of stimuli was needed to fully account for the improvements observed when backward masks followed the letter stimuli. Taken together, our results (i) are inconsistent with saccadic uncrowding, (ii) strongly support saccadic unmasking, and (iii) suggest that pre-saccadic letter recognition is modulated by multiple perisaccadic mechanisms with different time courses. |
C J Aine; H J Bockholt; J R Bustillo; J M Cañive; A Caprihan; C Gasparovic; F M Hanlon; J M Houck; R E Jung; J Lauriello; J Liu; A R Mayer; N I Perrone-Bizzozero; S Posse; J M Stephen; J A Turner; V P Clark; Vince D Calhoun Multimodal neuroimaging in schizophrenia: Description and dissemination Journal Article Neuroinformatics, 15 (4), pp. 343–364, 2017. @article{Aine2017, title = {Multimodal neuroimaging in schizophrenia: Description and dissemination}, author = {C J Aine and H J Bockholt and J R Bustillo and J M Ca{ñ}ive and A Caprihan and C Gasparovic and F M Hanlon and J M Houck and R E Jung and J Lauriello and J Liu and A R Mayer and N I Perrone-Bizzozero and S Posse and J M Stephen and J A Turner and V P Clark and Vince D Calhoun}, doi = {10.1007/s12021-017-9338-9}, year = {2017}, date = {2017-01-01}, journal = {Neuroinformatics}, volume = {15}, number = {4}, pages = {343--364}, publisher = {Neuroinformatics}, abstract = {In this paper we describe an open-access collection ofmultimodal neuroimaging data in schizophrenia for release to the community. Data were acquired from approximately 100 patients with schizophrenia and 100 age-matched controls during rest as well as several task activation paradigms targeting a hierarchy of cognitive constructs. Neuroimaging data include structural MRI, functional MRI, diffusion MRI, MR spectroscopic imaging, and magnetoencephalography. For three of the hypothesis-driven projects, task activation paradigms were acquired on subsets of~200 volunteers which examined a range of sensory and cognitive processes (e.g., auditory sensory gating, auditory/visual multisensory integration, visual transverse patterning). Neuropsychological data were also acquired and genetic material via saliva samples were collected from most of the participants and have been typed for both genome-wide polymorphism data as well as genome-wide methylation data. Some results are also present- ed from the individual studies as well as from our data-driven multimodal analyses (e.g., multimodal examinations of network structure and network dynamics and multitask fMRI data analysis across projects). All data will be released through the Mind Research Network's collaborative informatics and neuroimaging suite (COINS).}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this paper we describe an open-access collection ofmultimodal neuroimaging data in schizophrenia for release to the community. Data were acquired from approximately 100 patients with schizophrenia and 100 age-matched controls during rest as well as several task activation paradigms targeting a hierarchy of cognitive constructs. Neuroimaging data include structural MRI, functional MRI, diffusion MRI, MR spectroscopic imaging, and magnetoencephalography. For three of the hypothesis-driven projects, task activation paradigms were acquired on subsets of~200 volunteers which examined a range of sensory and cognitive processes (e.g., auditory sensory gating, auditory/visual multisensory integration, visual transverse patterning). Neuropsychological data were also acquired and genetic material via saliva samples were collected from most of the participants and have been typed for both genome-wide polymorphism data as well as genome-wide methylation data. Some results are also present- ed from the individual studies as well as from our data-driven multimodal analyses (e.g., multimodal examinations of network structure and network dynamics and multitask fMRI data analysis across projects). All data will be released through the Mind Research Network's collaborative informatics and neuroimaging suite (COINS). |
Cordelia D Aitkin; Elio M Santos; Eileen Kowler Anticipatory smooth eye movements in autism spectrum disorder Journal Article PLoS ONE, 8 (12), pp. 1–11, 2013. @article{Aitkin2013, title = {Anticipatory smooth eye movements in autism spectrum disorder}, author = {Cordelia D Aitkin and Elio M Santos and Eileen Kowler}, doi = {10.1371/journal.pone.0083230}, year = {2013}, date = {2013-01-01}, journal = {PLoS ONE}, volume = {8}, number = {12}, pages = {1--11}, abstract = {Smooth pursuit eye movements are important for vision because they maintain the line of sight on targets that move smoothly within the visual field. Smooth pursuit is driven by neural representations of motion, including a surprisingly strong influence of high-level signals representing expected motion. We studied anticipatory smooth eye movements (defined as smooth eye movements in the direction of expected future motion) produced by salient visual cues in a group of high-functioning observers with Autism Spectrum Disorder (ASD), a condition that has been associated with difficulties in either generating predictions, or translating predictions into effective motor commands. Eye movements were recorded while participants pursued the motion of a disc that moved within an outline drawing of an inverted Y-shaped tube. The cue to the motion path was a visual barrier that blocked the untraveled branch (right or left) of the tube. ASD participants showed strong anticipatory smooth eye movements whose velocity was the same as that of a group of neurotypical participants. Anticipatory smooth eye movements appeared on the very first cued trial, indicating that trial-by-trial learning was not responsible for the responses. These results are significant because they show that anticipatory capacities are intact in high-functioning ASD in cases where the cue to the motion path is highly salient and unambiguous. Once the ability to generate anticipatory pursuit is demonstrated, the study of the anticipatory responses with a variety of types of cues provides a window into the perceptual or cognitive processes that underlie the interpretation of events in natural environments or social situations.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Smooth pursuit eye movements are important for vision because they maintain the line of sight on targets that move smoothly within the visual field. Smooth pursuit is driven by neural representations of motion, including a surprisingly strong influence of high-level signals representing expected motion. We studied anticipatory smooth eye movements (defined as smooth eye movements in the direction of expected future motion) produced by salient visual cues in a group of high-functioning observers with Autism Spectrum Disorder (ASD), a condition that has been associated with difficulties in either generating predictions, or translating predictions into effective motor commands. Eye movements were recorded while participants pursued the motion of a disc that moved within an outline drawing of an inverted Y-shaped tube. The cue to the motion path was a visual barrier that blocked the untraveled branch (right or left) of the tube. ASD participants showed strong anticipatory smooth eye movements whose velocity was the same as that of a group of neurotypical participants. Anticipatory smooth eye movements appeared on the very first cued trial, indicating that trial-by-trial learning was not responsible for the responses. These results are significant because they show that anticipatory capacities are intact in high-functioning ASD in cases where the cue to the motion path is highly salient and unambiguous. Once the ability to generate anticipatory pursuit is demonstrated, the study of the anticipatory responses with a variety of types of cues provides a window into the perceptual or cognitive processes that underlie the interpretation of events in natural environments or social situations. |
Sara Ajina; Franco Pestilli; Ariel Rokem; Christopher Kennard; Holly Bridge Human blindsight is mediated by an intact geniculo-extrastriate pathway Journal Article eLife, 4 , pp. 1–23, 2015. @article{Ajina2015a, title = {Human blindsight is mediated by an intact geniculo-extrastriate pathway}, author = {Sara Ajina and Franco Pestilli and Ariel Rokem and Christopher Kennard and Holly Bridge}, doi = {10.7554/eLife.08935}, year = {2015}, date = {2015-01-01}, journal = {eLife}, volume = {4}, pages = {1--23}, abstract = {Although damage to the primary visual cortex (V1) causes hemianopia, many patients retain some residual vision; known as blindsight. We show that blindsight may be facilitated by an intact white-matter pathway between the lateral geniculate nucleus and motion area hMT+. Visual psychophysics, diffusion-weighted magnetic resonance imaging and fibre tractography were applied in 17 patients with V1 damage acquired during adulthood and 9 age-matched controls. Individuals with V1 damage were subdivided into blindsight positive (preserved residual vision) and negative (no residual vision) according to psychophysical performance. All blindsight positive individuals showed intact geniculo-hMT+ pathways, while this pathway was significantly impaired or not measurable in blindsight negative individuals. Two white matter pathways previously implicated in blindsight: (i) superior colliculus to hMT+ and (ii) between hMT+ in each hemisphere were not consistently present in blindsight positive cases. Understanding the visual pathways crucial for residual vision may direct future rehabilitation strategies for hemianopia patients.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Although damage to the primary visual cortex (V1) causes hemianopia, many patients retain some residual vision; known as blindsight. We show that blindsight may be facilitated by an intact white-matter pathway between the lateral geniculate nucleus and motion area hMT+. Visual psychophysics, diffusion-weighted magnetic resonance imaging and fibre tractography were applied in 17 patients with V1 damage acquired during adulthood and 9 age-matched controls. Individuals with V1 damage were subdivided into blindsight positive (preserved residual vision) and negative (no residual vision) according to psychophysical performance. All blindsight positive individuals showed intact geniculo-hMT+ pathways, while this pathway was significantly impaired or not measurable in blindsight negative individuals. Two white matter pathways previously implicated in blindsight: (i) superior colliculus to hMT+ and (ii) between hMT+ in each hemisphere were not consistently present in blindsight positive cases. Understanding the visual pathways crucial for residual vision may direct future rehabilitation strategies for hemianopia patients. |
Sara Ajina; Geraint Rees; Christopher Kennard; Holly Bridge Abnormal contrast responses in the extrastriate cortex of blindsight patients Journal Article Journal of Neuroscience, 35 (21), pp. 8201–8213, 2015. @article{Ajina2015b, title = {Abnormal contrast responses in the extrastriate cortex of blindsight patients}, author = {Sara Ajina and Geraint Rees and Christopher Kennard and Holly Bridge}, doi = {10.1523/JNEUROSCI.3075-14.2015}, year = {2015}, date = {2015-01-01}, journal = {Journal of Neuroscience}, volume = {35}, number = {21}, pages = {8201--8213}, abstract = {When the human primary visual cortex (V1) is damaged, the dominant geniculo-striate pathway can no longer convey visual information to the occipital cortex. However, many patients with such damage retain some residual visual function that must rely on an alternative pathway directly to extrastriate occipital regions. This residual vision is most robust for moving stimuli, suggesting a role for motion area hMT+. However, residual vision also requires high-contrast stimuli, which is inconsistent with hMT+ sensitivity to contrast in which even low-contrast levels elicit near-maximal neural activation. We sought to investigate this discrepancy by measuring behavioral and neural responses to increasing contrast in patients with V1 damage. Eight patients underwent behavioral testing and functional magnetic resonance imaging to record contrast sensitivity in hMT+ of their damaged hemisphere, using Gabor stimuli with a spatial frequency of 1 cycle/degrees. The responses from hMT+ of the blind hemisphere were compared with hMT+ and V1 responses in the sighted hemisphere of patients and a group of age-matched controls. Unlike hMT+, neural responses in V1 tend to increase linearly with increasing contrast, likely reflecting a dominant parvocellular channel input. Across all patients, the responses in hMT+ of the blind hemisphere no longer showed early saturation but increased linearly with contrast. Given the spatiotemporal parameters used in this study and the known direct subcortical projections from the koniocellular layers of the lateral geniculate nucleus to hMT+, we propose that this altered contrast sensitivity in hMT+ could be consistent with input from the koniocellular pathway.}, keywords = {}, pubstate = {published}, tppubtype = {article} } When the human primary visual cortex (V1) is damaged, the dominant geniculo-striate pathway can no longer convey visual information to the occipital cortex. However, many patients with such damage retain some residual visual function that must rely on an alternative pathway directly to extrastriate occipital regions. This residual vision is most robust for moving stimuli, suggesting a role for motion area hMT+. However, residual vision also requires high-contrast stimuli, which is inconsistent with hMT+ sensitivity to contrast in which even low-contrast levels elicit near-maximal neural activation. We sought to investigate this discrepancy by measuring behavioral and neural responses to increasing contrast in patients with V1 damage. Eight patients underwent behavioral testing and functional magnetic resonance imaging to record contrast sensitivity in hMT+ of their damaged hemisphere, using Gabor stimuli with a spatial frequency of 1 cycle/degrees. The responses from hMT+ of the blind hemisphere were compared with hMT+ and V1 responses in the sighted hemisphere of patients and a group of age-matched controls. Unlike hMT+, neural responses in V1 tend to increase linearly with increasing contrast, likely reflecting a dominant parvocellular channel input. Across all patients, the responses in hMT+ of the blind hemisphere no longer showed early saturation but increased linearly with contrast. Given the spatiotemporal parameters used in this study and the known direct subcortical projections from the koniocellular layers of the lateral geniculate nucleus to hMT+, we propose that this altered contrast sensitivity in hMT+ could be consistent with input from the koniocellular pathway. |
Sara Ajina; Holly Bridge Blindsight relies on a functional connection between hMT+ and the lateral geniculate nucleus, not the pulvinar Journal Article PLoS Biology, 16 (7), pp. 1–25, 2018. @article{Ajina2018, title = {Blindsight relies on a functional connection between hMT+ and the lateral geniculate nucleus, not the pulvinar}, author = {Sara Ajina and Holly Bridge}, doi = {10.1371/journal.pbio.2005769}, year = {2018}, date = {2018-01-01}, journal = {PLoS Biology}, volume = {16}, number = {7}, pages = {1--25}, abstract = {When the primary visual cortex (V1) is damaged, the principal visual pathway is lost, causing a loss of vision in the opposite visual field. While conscious vision is impaired, patients can still respond to certain images; this is known as ‘blindsight'. Recently, a direct anatomical connection between the lateral geniculate nucleus (LGN) and human motion area hMT+ has been implicated in blindsight. However, a functional connection between these structures has not been demonstrated. We quantified functional MRI responses to motion in 14 patients with unilateral V1 damage (with and without blindsight). Patients with blindsight showed significant activity and a preserved sensitivity to speed in motion area hMT+, which was absent in patients without blindsight. We then compared functional connectivity between motion area hMT+ and a number of structures implicated in blindsight, including the ventral pulvinar. Only patients with blindsight showed an intact functional connection with the LGN but not the other structures, supporting a specific functional role for the LGN in blindsight.}, keywords = {}, pubstate = {published}, tppubtype = {article} } When the primary visual cortex (V1) is damaged, the principal visual pathway is lost, causing a loss of vision in the opposite visual field. While conscious vision is impaired, patients can still respond to certain images; this is known as ‘blindsight'. Recently, a direct anatomical connection between the lateral geniculate nucleus (LGN) and human motion area hMT+ has been implicated in blindsight. However, a functional connection between these structures has not been demonstrated. We quantified functional MRI responses to motion in 14 patients with unilateral V1 damage (with and without blindsight). Patients with blindsight showed significant activity and a preserved sensitivity to speed in motion area hMT+, which was absent in patients without blindsight. We then compared functional connectivity between motion area hMT+ and a number of structures implicated in blindsight, including the ventral pulvinar. Only patients with blindsight showed an intact functional connection with the LGN but not the other structures, supporting a specific functional role for the LGN in blindsight. |
Umair Akram; Jason G Ellis; Andriy Myachykov; Nicola L Barclay Preferential attention towards the eye-region amongst individuals with insomnia Journal Article Journal of Sleep Research, 26 (1), pp. 84–91, 2017. @article{Akram2017, title = {Preferential attention towards the eye-region amongst individuals with insomnia}, author = {Umair Akram and Jason G Ellis and Andriy Myachykov and Nicola L Barclay}, doi = {10.1111/jsr.12456}, year = {2017}, date = {2017-01-01}, journal = {Journal of Sleep Research}, volume = {26}, number = {1}, pages = {84--91}, abstract = {People with insomnia often perceive their own facial appearance as more tired compared with the appearance of others. Evidence also highlights the eye-region in projecting tiredness cues to perceivers, and tiredness judgements often rely on preferential attention towards this region. Using a novel eye-tracking paradigm, this study examined: (i) whether individuals with insomnia display preferential attention towards the eyeregion, relative to nose and mouth regions, whilst observing faces compared with normal-sleepers; and (ii) whether an attentional bias towards the eye-region amongst individuals with insomnia is self-specific or general in nature. Twenty individuals with DSM-5 Insomnia Disorder and 20 normal-sleepers viewed 48 neutral facial photographs (24 of themselves, 24 of other people) for periods of 4000 ms. Eye movements were recorded using eye-tracking, and first fixation onset, first fixation duration and total gaze duration were examined for three interest-regions (eyes, nose, mouth). Significant group 9 interest-region interactions indicated that, regardless of the face presented, participants with insomnia were quicker to attend to, and spent more time observing, the eye-region relative to the nose and mouth regions compared with normal-sleepers. However, no group 9 face 9 interest-region interactions were established. Thus, whilst individuals with insomnia displayed preferential attention towards the eye-region in general, this effect was not accentuated during self-perception. Insomnia appears to be characterized by a general, rather than self-specific, attentional bias towards the eye-region. These findings contribute to our understanding of face perception in insomnia, and provide tentative support for cognitive models of insomnia demonstrating that individuals with insomnia monitor faces in general, with a specific focus around the eye-region, for cues associated with tiredness.}, keywords = {}, pubstate = {published}, tppubtype = {article} } People with insomnia often perceive their own facial appearance as more tired compared with the appearance of others. Evidence also highlights the eye-region in projecting tiredness cues to perceivers, and tiredness judgements often rely on preferential attention towards this region. Using a novel eye-tracking paradigm, this study examined: (i) whether individuals with insomnia display preferential attention towards the eyeregion, relative to nose and mouth regions, whilst observing faces compared with normal-sleepers; and (ii) whether an attentional bias towards the eye-region amongst individuals with insomnia is self-specific or general in nature. Twenty individuals with DSM-5 Insomnia Disorder and 20 normal-sleepers viewed 48 neutral facial photographs (24 of themselves, 24 of other people) for periods of 4000 ms. Eye movements were recorded using eye-tracking, and first fixation onset, first fixation duration and total gaze duration were examined for three interest-regions (eyes, nose, mouth). Significant group 9 interest-region interactions indicated that, regardless of the face presented, participants with insomnia were quicker to attend to, and spent more time observing, the eye-region relative to the nose and mouth regions compared with normal-sleepers. However, no group 9 face 9 interest-region interactions were established. Thus, whilst individuals with insomnia displayed preferential attention towards the eye-region in general, this effect was not accentuated during self-perception. Insomnia appears to be characterized by a general, rather than self-specific, attentional bias towards the eye-region. These findings contribute to our understanding of face perception in insomnia, and provide tentative support for cognitive models of insomnia demonstrating that individuals with insomnia monitor faces in general, with a specific focus around the eye-region, for cues associated with tiredness. |
Naseem Al-aidroos; Jos J Adam; Martin H Fischer; Jay Pratt Structured perceptual arrays and the modulation of Fitts's Law: Examining saccadic eye movements Journal Article Journal of Motor Behavior, 40 (2), pp. 155–164, 2008. @article{Al-aidroos2008, title = {Structured perceptual arrays and the modulation of Fitts's Law: Examining saccadic eye movements}, author = {Naseem Al-aidroos and Jos J Adam and Martin H Fischer and Jay Pratt}, year = {2008}, date = {2008-01-01}, journal = {Journal of Motor Behavior}, volume = {40}, number = {2}, pages = {155--164}, abstract = {On the basis of recent observations of a modulation of Fitts's law for manual pointing movements in structured visual arrays (J. J. Adam, R. Mol, J. Pratt, & M. H. Fischer, 2006; J. Pratt, J. J. Adam, & M. H. Fischer, 2007), the authors examined whether a similar modulation occurs for saccadic eye move- ments. Healthy participants (N = 19) made horizontal saccades to targets that appeared randomly in 1 of 4 positions, either on an empty background or within 1 of 4 placeholder boxes. Whereas in previous studies, placeholders caused a decrease in movement time (MT) without the normal decrease in movement accuracy predicted by Fitts's law, placeholders in the present experiment increased saccadic accuracy (decreased endpoint variability) with- out an increase in MT. The present results extend the findings of J. J. Adam et al. of a modulation of Fitts's law from the temporal domain to the spatial domain and from manual movements to eye movements.}, keywords = {}, pubstate = {published}, tppubtype = {article} } On the basis of recent observations of a modulation of Fitts's law for manual pointing movements in structured visual arrays (J. J. Adam, R. Mol, J. Pratt, & M. H. Fischer, 2006; J. Pratt, J. J. Adam, & M. H. Fischer, 2007), the authors examined whether a similar modulation occurs for saccadic eye move- ments. Healthy participants (N = 19) made horizontal saccades to targets that appeared randomly in 1 of 4 positions, either on an empty background or within 1 of 4 placeholder boxes. Whereas in previous studies, placeholders caused a decrease in movement time (MT) without the normal decrease in movement accuracy predicted by Fitts's law, placeholders in the present experiment increased saccadic accuracy (decreased endpoint variability) with- out an increase in MT. The present results extend the findings of J. J. Adam et al. of a modulation of Fitts's law from the temporal domain to the spatial domain and from manual movements to eye movements. |
Naseem Al-Aidroos; Jay Pratt Top-down control in time and space: Evidence from saccadic latencies and trajectories Journal Article Visual Cognition, 18 (1), pp. 26–49, 2010. @article{Al-Aidroos2010, title = {Top-down control in time and space: Evidence from saccadic latencies and trajectories}, author = {Naseem Al-Aidroos and Jay Pratt}, doi = {10.1080/13506280802456939}, year = {2010}, date = {2010-01-01}, journal = {Visual Cognition}, volume = {18}, number = {1}, pages = {26--49}, abstract = {Visual distractors disrupt the production of saccadic eye movements temporally, by increasing saccade latency, and spatially, by biasing the trajectory of the movement. The present research investigated the extent to which top-down control can be exerted over these two forms of oculomotor capture. In two experiments, people were instructed to make target directed saccades in the presence of distractors, and temporal and spatial capture were assessed simultaneously by measuring saccade latency and saccade trajectory curvature, respectively. In Experiment 1, an attentional control set manipulation was employed, resulting in the elimination of temporal capture, but only an attenuation of spatial capture. In Experiment 2, foreknowledge of the target location caused an attenuation of temporal capture but an enhancement of spatial capture. These results suggest that, whereas temporal capture is contingent on top-down control, the spatial component of capture is stimulus-driven.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Visual distractors disrupt the production of saccadic eye movements temporally, by increasing saccade latency, and spatially, by biasing the trajectory of the movement. The present research investigated the extent to which top-down control can be exerted over these two forms of oculomotor capture. In two experiments, people were instructed to make target directed saccades in the presence of distractors, and temporal and spatial capture were assessed simultaneously by measuring saccade latency and saccade trajectory curvature, respectively. In Experiment 1, an attentional control set manipulation was employed, resulting in the elimination of temporal capture, but only an attenuation of spatial capture. In Experiment 2, foreknowledge of the target location caused an attenuation of temporal capture but an enhancement of spatial capture. These results suggest that, whereas temporal capture is contingent on top-down control, the spatial component of capture is stimulus-driven. |
Nadia Alahyane; Denis Pélisson Adaptation of saccadic eye movements: Transfer and specificity Journal Article Annals of New York Academy of Sciences, 1004 (1), pp. 69–77, 2003. @article{Alahyane2003, title = {Adaptation of saccadic eye movements: Transfer and specificity}, author = {Nadia Alahyane and Denis Pélisson}, doi = {10.1196/annals.1303.008}, year = {2003}, date = {2003-01-01}, journal = {Annals of New York Academy of Sciences}, volume = {1004}, number = {1}, pages = {69--77}, abstract = {The present study was designed to test whether the adaptation of saccadic eye movements depends only on the eye displacement vector of the trained saccade or also on eye position information. Using the double-step target paradigm in eight human subjects, we first induced in a single session two "opposite directions adaptations" (ODA) of horizontal saccades of the same vector. Each ODA (backward or forward) was linked to one vertical eye position (12.5 degrees up or 25 degrees down) and alternated from trial to trial. The results showed that opposite changes of saccade amplitude can develop simultaneously, indicating that saccadic adaptation depends on orbital eye position. This finding has important functional implications because in everyday life our eyes saccade from constantly changing orbital positions. A comparison of these data to two control conditions in which training trials of a single type (backward or forward) were presented at both 12.5 degrees and -25 degrees eye elevations further indicated that eye position specificity is complete for backward, but not for forward, adaptation. Finally, the control conditions also indicated that the adaptation of a single saccade fully transferred to untrained saccades of the same vector, but initiated from different vertical eye positions. In conclusion, our study indicates that saccadic adaptation mechanisms use vectorial eye displacement signals, but can also take eye position signals into account as a contextual cue when the training involves conflicting saccade amplitude changes}, keywords = {}, pubstate = {published}, tppubtype = {article} } The present study was designed to test whether the adaptation of saccadic eye movements depends only on the eye displacement vector of the trained saccade or also on eye position information. Using the double-step target paradigm in eight human subjects, we first induced in a single session two "opposite directions adaptations" (ODA) of horizontal saccades of the same vector. Each ODA (backward or forward) was linked to one vertical eye position (12.5 degrees up or 25 degrees down) and alternated from trial to trial. The results showed that opposite changes of saccade amplitude can develop simultaneously, indicating that saccadic adaptation depends on orbital eye position. This finding has important functional implications because in everyday life our eyes saccade from constantly changing orbital positions. A comparison of these data to two control conditions in which training trials of a single type (backward or forward) were presented at both 12.5 degrees and -25 degrees eye elevations further indicated that eye position specificity is complete for backward, but not for forward, adaptation. Finally, the control conditions also indicated that the adaptation of a single saccade fully transferred to untrained saccades of the same vector, but initiated from different vertical eye positions. In conclusion, our study indicates that saccadic adaptation mechanisms use vectorial eye displacement signals, but can also take eye position signals into account as a contextual cue when the training involves conflicting saccade amplitude changes |
Nadia Alahyane; Ansgar Koene; Denis Pélisson Transfer of adaptation from visually guided saccades to averaging saccades elicited by double visual targets Journal Article European Journal of Neuroscience, 20 (3), pp. 827–836, 2004. @article{Alahyane2004, title = {Transfer of adaptation from visually guided saccades to averaging saccades elicited by double visual targets}, author = {Nadia Alahyane and Ansgar Koene and Denis Pélisson}, doi = {10.1111/j.1460-9568.2004.03536.x}, year = {2004}, date = {2004-01-01}, journal = {European Journal of Neuroscience}, volume = {20}, number = {3}, pages = {827--836}, abstract = {The adaptive mechanisms that control the amplitude of visually guided saccades (VGS) are only partially elucidated. In this study, we investigated, in six human subjects, the transfer of VGS adaptation to averaging saccades elicited by the simultaneous presentation of two visual targets. The generation of averaging saccades requires the transformation of two representations encoding the desired eye displacement toward each of the two targets into a single representation encoding the averaging saccade (averaging programming site). We aimed to evaluate whether VGS adaptation acts upstream (hypothesis 1) or at/below (hypothesis 2) the level of averaging saccades programming. Using the double-step target paradigm, we simultaneously induced a backward adaptation of 17.5 degrees horizontal VGS and a forward adaptation of 17.5 degrees oblique VGS performed along the +/- 40 degrees directions relative to the azimuth. We measured the effects of this dual adaptation protocol on averaging saccades triggered by two simultaneous targets located at 17.5 degrees along the +/- 40 degrees directions. To increase the yield of averaging saccades, we instructed the subjects to move their eyes as fast as possible to an intermediate position between the two targets. We found that the amplitude of averaging saccades was smaller after VGS adaptation than before and differed significantly from that predicted by hypothesis 1, but not by hypothesis 2, with an adaptation transfer of 50%. These findings indicate that VGS adaptation largely occurs at/below the averaging saccade programming site. Based on current knowledge of the neural substrate of averaging saccades, we suggest that VGS adaptation mainly acts at the level of the superior colliculus or downstream.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The adaptive mechanisms that control the amplitude of visually guided saccades (VGS) are only partially elucidated. In this study, we investigated, in six human subjects, the transfer of VGS adaptation to averaging saccades elicited by the simultaneous presentation of two visual targets. The generation of averaging saccades requires the transformation of two representations encoding the desired eye displacement toward each of the two targets into a single representation encoding the averaging saccade (averaging programming site). We aimed to evaluate whether VGS adaptation acts upstream (hypothesis 1) or at/below (hypothesis 2) the level of averaging saccades programming. Using the double-step target paradigm, we simultaneously induced a backward adaptation of 17.5 degrees horizontal VGS and a forward adaptation of 17.5 degrees oblique VGS performed along the +/- 40 degrees directions relative to the azimuth. We measured the effects of this dual adaptation protocol on averaging saccades triggered by two simultaneous targets located at 17.5 degrees along the +/- 40 degrees directions. To increase the yield of averaging saccades, we instructed the subjects to move their eyes as fast as possible to an intermediate position between the two targets. We found that the amplitude of averaging saccades was smaller after VGS adaptation than before and differed significantly from that predicted by hypothesis 1, but not by hypothesis 2, with an adaptation transfer of 50%. These findings indicate that VGS adaptation largely occurs at/below the averaging saccade programming site. Based on current knowledge of the neural substrate of averaging saccades, we suggest that VGS adaptation mainly acts at the level of the superior colliculus or downstream. |
Nadia Alahyane; Denis Pélisson Eye position specificity of saccadic adaptation Journal Article Investigative Ophthalmology & Visual Science, 45 (1), pp. 123–130, 2004. @article{Alahyane2004a, title = {Eye position specificity of saccadic adaptation}, author = {Nadia Alahyane and Denis Pélisson}, doi = {10.1167/iovs.03-0570}, year = {2004}, date = {2004-01-01}, journal = {Investigative Ophthalmology & Visual Science}, volume = {45}, number = {1}, pages = {123--130}, abstract = {PURPOSE: The accuracy of saccadic eye movements is maintained throughout life by adaptive mechanisms. With the double-step target paradigm, eight human subjects were investigated to determine whether saccadic adaptation depends only on the eye-displacement vector, or also on eye position as a context cue when two saccades of identical vector are adapted simultaneously. METHODS: First, bidirectional adaptations (BDAs) of horizontal saccades of the same vector were induced in a single training phase. Each direction of adaptation in BDAs (backward and forward) was linked to one vertical eye position (e.g., forward adaptation performed with the eyes directed 12.5 degrees upward and backward adaptation with the eyes 25 degrees downward) and alternated from trial to trial. Second, unidirectional adaptations (UDAs) were tested in two control conditions in which training trials of a single direction (backward or forward) were presented at both 12.5 degrees and -25 degrees eye elevations. RESULTS: Opposite changes in saccade amplitude could develop simultaneously in BDA, indicating that saccadic adaptation depends on orbital eye position. Comparing these data with the control conditions further indicated that eye position specificity was complete for backward, but not for forward, adaptation. CONCLUSIONS: The results indicate that saccadic adaptation mechanisms use vectorial eye displacement signals, but can also take eye position signals into account as a contextual cue when the training involves conflicting saccade amplitude changes.}, keywords = {}, pubstate = {published}, tppubtype = {article} } PURPOSE: The accuracy of saccadic eye movements is maintained throughout life by adaptive mechanisms. With the double-step target paradigm, eight human subjects were investigated to determine whether saccadic adaptation depends only on the eye-displacement vector, or also on eye position as a context cue when two saccades of identical vector are adapted simultaneously. METHODS: First, bidirectional adaptations (BDAs) of horizontal saccades of the same vector were induced in a single training phase. Each direction of adaptation in BDAs (backward and forward) was linked to one vertical eye position (e.g., forward adaptation performed with the eyes directed 12.5 degrees upward and backward adaptation with the eyes 25 degrees downward) and alternated from trial to trial. Second, unidirectional adaptations (UDAs) were tested in two control conditions in which training trials of a single direction (backward or forward) were presented at both 12.5 degrees and -25 degrees eye elevations. RESULTS: Opposite changes in saccade amplitude could develop simultaneously in BDA, indicating that saccadic adaptation depends on orbital eye position. Comparing these data with the control conditions further indicated that eye position specificity was complete for backward, but not for forward, adaptation. CONCLUSIONS: The results indicate that saccadic adaptation mechanisms use vectorial eye displacement signals, but can also take eye position signals into account as a contextual cue when the training involves conflicting saccade amplitude changes. |
Nadia Alahyane; Denis Pélisson Retention of saccadic adaptation in humans Journal Article Annals of the New York Academy of Sciences, 1039 , pp. 558–562, 2005. @article{Alahyane2005, title = {Retention of saccadic adaptation in humans}, author = {Nadia Alahyane and Denis Pélisson}, doi = {10.1196/annals.1325.067}, year = {2005}, date = {2005-01-01}, journal = {Annals of the New York Academy of Sciences}, volume = {1039}, pages = {558--562}, abstract = {In the present study, we tested in human subjects the persistence of the oculomotor changes resulting from saccadic adaptation up to 19 days after exposure to the double step target protocol. The main results indicate that the reduction of saccade gain related to the adaptation session (mean gain change of 5 subjects = 22 +/- 4.7%) was partially but significantly retained after 1 day and 5 days (mean amount of retention = 36 +/- 17% and 19.7 +/- 13.3%, respectively) but was no longer significant at day 11 and 19. Unexpectedly, gain changes were larger for leftward than for rightward saccades. No change in saccade dynamics was observed. These data suggest that in humans, adaptive mechanisms induce long lasting changes in visually-guided saccade amplitude, probably reflecting plastic changes in the brain.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In the present study, we tested in human subjects the persistence of the oculomotor changes resulting from saccadic adaptation up to 19 days after exposure to the double step target protocol. The main results indicate that the reduction of saccade gain related to the adaptation session (mean gain change of 5 subjects = 22 +/- 4.7%) was partially but significantly retained after 1 day and 5 days (mean amount of retention = 36 +/- 17% and 19.7 +/- 13.3%, respectively) but was no longer significant at day 11 and 19. Unexpectedly, gain changes were larger for leftward than for rightward saccades. No change in saccade dynamics was observed. These data suggest that in humans, adaptive mechanisms induce long lasting changes in visually-guided saccade amplitude, probably reflecting plastic changes in the brain. |
Nadia Alahyane; Denis Pélisson Long-lasting modifications of saccadic eye movements following adaptation induced in the double-step target paradigm Journal Article Learning and Memory, 12 (4), pp. 433–443, 2005. @article{Alahyane2005a, title = {Long-lasting modifications of saccadic eye movements following adaptation induced in the double-step target paradigm}, author = {Nadia Alahyane and Denis Pélisson}, doi = {10.1101/lm.96405}, year = {2005}, date = {2005-01-01}, journal = {Learning and Memory}, volume = {12}, number = {4}, pages = {433--443}, abstract = {The adaptation of saccadic eye movements to environmental changes occurring throughout life is a good model of motor learning and motor memory. Numerous studies have analyzed the behavioral properties and neural substrate of oculomotor learning in short-term saccadic adaptation protocols, but to our knowledge, none have tested the persistence of the oculomotor memory. In the present study, the double-step target protocol was used in five human subjects to adaptively decrease the amplitude of reactive saccades triggered by a horizontally-stepping visual target. We tested the amplitude of visually guided saccades just before and at different times (up to 19 days) after the adaptation session. The results revealed that immediately after the adaptation session, saccade amplitude was significantly reduced by 22% on average. Although progressively recovering over days, this change in saccade gain was still statistically significant on days 1 and 5, with an average retention rate of 36% and 19%, respectively. On day 11, saccade amplitude no longer differed from the pre-adaptation value. Adaptation was more effective and more resistant to recovery for leftward saccades than for rightward ones. Lastly, modifications of saccade gain related to adaptation were accompanied by a decrease of both saccade duration and peak velocity. A control experiment indicated that all these findings were specifically related to the adaptation protocol, and further revealed that no change in the main sequence relationships could be specifically related to adaptation. We conclude that in humans, the modifications of saccade amplitude that quickly develop during a double-step target adaptation protocol can remain in memory for a much longer period of time, reflecting enduring plastic changes in the brain.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The adaptation of saccadic eye movements to environmental changes occurring throughout life is a good model of motor learning and motor memory. Numerous studies have analyzed the behavioral properties and neural substrate of oculomotor learning in short-term saccadic adaptation protocols, but to our knowledge, none have tested the persistence of the oculomotor memory. In the present study, the double-step target protocol was used in five human subjects to adaptively decrease the amplitude of reactive saccades triggered by a horizontally-stepping visual target. We tested the amplitude of visually guided saccades just before and at different times (up to 19 days) after the adaptation session. The results revealed that immediately after the adaptation session, saccade amplitude was significantly reduced by 22% on average. Although progressively recovering over days, this change in saccade gain was still statistically significant on days 1 and 5, with an average retention rate of 36% and 19%, respectively. On day 11, saccade amplitude no longer differed from the pre-adaptation value. Adaptation was more effective and more resistant to recovery for leftward saccades than for rightward ones. Lastly, modifications of saccade gain related to adaptation were accompanied by a decrease of both saccade duration and peak velocity. A control experiment indicated that all these findings were specifically related to the adaptation protocol, and further revealed that no change in the main sequence relationships could be specifically related to adaptation. We conclude that in humans, the modifications of saccade amplitude that quickly develop during a double-step target adaptation protocol can remain in memory for a much longer period of time, reflecting enduring plastic changes in the brain. |
Nadia Alahyane; Roméo Salemme; Christian Urquizar; Julien Cotti; Alain Guillaume; Jean-Louis Vercher; Denis Pélisson Oculomotor plasticity: Are mechanisms of adaptation for reactive and voluntary saccades separate? Journal Article Brain Research, 1135 (1), pp. 107–121, 2007. @article{Alahyane2007, title = {Oculomotor plasticity: Are mechanisms of adaptation for reactive and voluntary saccades separate?}, author = {Nadia Alahyane and Roméo Salemme and Christian Urquizar and Julien Cotti and Alain Guillaume and Jean-Louis Vercher and Denis Pélisson}, doi = {10.1016/j.brainres.2006.11.077}, year = {2007}, date = {2007-01-01}, journal = {Brain Research}, volume = {1135}, number = {1}, pages = {107--121}, abstract = {Saccadic eye movements are permanently controlled and their accuracy maintained by adaptive mechanisms that compensate for physiological or pathological perturbations. In contrast to the adaptation of reactive saccades (RS) which are automatically triggered by the sudden appearance of a single target, little is known about the adaptation of voluntary saccades which allow us to intentionally scan our environment in nearly all our daily activities. In this study, we addressed this issue in human subjects by determining the properties of adaptation of scanning voluntary saccades (SVS) and comparing these features to those of RS. We also tested the reciprocal transfers of adaptation between the two saccade types. Our results revealed that SVS and RS adaptations disclosed similar adaptation fields, time course and recovery levels, with only a slightly lower after-effect for SVS. Moreover, RS and SVS main sequences both remained unaffected after adaptation. Finally and quite unexpectedly, the pattern of adaptation transfers was asymmetrical, with a much stronger transfer from SVS to RS (79%) than in the reverse direction (22%). These data demonstrate that adaptations of RS and SVS share several behavioural properties but at the same time rely on partially distinct processes. Based on these findings, it is proposed that adaptations of RS and SVS may involve a neural network including both a common site and two separate sites specifically recruited for each saccade type.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Saccadic eye movements are permanently controlled and their accuracy maintained by adaptive mechanisms that compensate for physiological or pathological perturbations. In contrast to the adaptation of reactive saccades (RS) which are automatically triggered by the sudden appearance of a single target, little is known about the adaptation of voluntary saccades which allow us to intentionally scan our environment in nearly all our daily activities. In this study, we addressed this issue in human subjects by determining the properties of adaptation of scanning voluntary saccades (SVS) and comparing these features to those of RS. We also tested the reciprocal transfers of adaptation between the two saccade types. Our results revealed that SVS and RS adaptations disclosed similar adaptation fields, time course and recovery levels, with only a slightly lower after-effect for SVS. Moreover, RS and SVS main sequences both remained unaffected after adaptation. Finally and quite unexpectedly, the pattern of adaptation transfers was asymmetrical, with a much stronger transfer from SVS to RS (79%) than in the reverse direction (22%). These data demonstrate that adaptations of RS and SVS share several behavioural properties but at the same time rely on partially distinct processes. Based on these findings, it is proposed that adaptations of RS and SVS may involve a neural network including both a common site and two separate sites specifically recruited for each saccade type. |
N Alahyane; V Fonteille; C Urquizar; R Salemme; N Nighoghossian; D Pelisson; C Tilikete Separate neural substrates in the human cerebellum for sensory-motor adaptation of reactive and of scanning voluntary saccades Journal Article Cerebellum, 7 (4), pp. 595–601, 2008. @article{Alahyane2008a, title = {Separate neural substrates in the human cerebellum for sensory-motor adaptation of reactive and of scanning voluntary saccades}, author = {N Alahyane and V Fonteille and C Urquizar and R Salemme and N Nighoghossian and D Pelisson and C Tilikete}, doi = {10.1007/s12311-008-0065-5}, year = {2008}, date = {2008-01-01}, journal = {Cerebellum}, volume = {7}, number = {4}, pages = {595--601}, abstract = {Sensory-motor adaptation processes are critically involved in maintaining accurate motor behavior throughout life. Yet their underlying neural substrates and task-dependency bases are still poorly understood. We address these issues here by studying adaptation of saccadic eye movements, a well-established model of sensory-motor plasticity. The cerebellum plays a major role in saccadic adaptation but it has not yet been investigated whether this role can account for the known specificity of adaptation to the saccade type (e.g., reactive versus voluntary). Two patients with focal lesions in different parts of the cerebellum were tested using the double-step target paradigm. Each patient was submitted to two separate sessions: one for reactive saccades (RS) triggered by the sudden appearance of a visual target and the second for scanning voluntary saccades (SVS) performed when exploring a more complex scene. We found that a medial cerebellar lesion impaired adaptation of reactive-but not of voluntary-saccades, whereas a lateral lesion affected adaptation of scanning voluntary saccades, but not of reactive saccades. These findings provide the first evidence of an involvement of the lateral cerebellum in saccadic adaptation, and extend the demonstrated role of the cerebellum in RS adaptation to adaptation of SVS. The double dissociation of adaptive abilities is also consistent with our previous hypothesis of the involvement in saccadic adaptation of partially separated cerebellar areas specific to the reactive or voluntary task (Alahyane et al. Brain Res 1135:107-121 (2007)).}, keywords = {}, pubstate = {published}, tppubtype = {article} } Sensory-motor adaptation processes are critically involved in maintaining accurate motor behavior throughout life. Yet their underlying neural substrates and task-dependency bases are still poorly understood. We address these issues here by studying adaptation of saccadic eye movements, a well-established model of sensory-motor plasticity. The cerebellum plays a major role in saccadic adaptation but it has not yet been investigated whether this role can account for the known specificity of adaptation to the saccade type (e.g., reactive versus voluntary). Two patients with focal lesions in different parts of the cerebellum were tested using the double-step target paradigm. Each patient was submitted to two separate sessions: one for reactive saccades (RS) triggered by the sudden appearance of a visual target and the second for scanning voluntary saccades (SVS) performed when exploring a more complex scene. We found that a medial cerebellar lesion impaired adaptation of reactive-but not of voluntary-saccades, whereas a lateral lesion affected adaptation of scanning voluntary saccades, but not of reactive saccades. These findings provide the first evidence of an involvement of the lateral cerebellum in saccadic adaptation, and extend the demonstrated role of the cerebellum in RS adaptation to adaptation of SVS. The double dissociation of adaptive abilities is also consistent with our previous hypothesis of the involvement in saccadic adaptation of partially separated cerebellar areas specific to the reactive or voluntary task (Alahyane et al. Brain Res 1135:107-121 (2007)). |
Nadia Alahyane; Anne-Dominique Devauchelle; Roméo Salemme; Denis Pélisson Spatial transfer of adaptation of scanning voluntary saccades in humans Journal Article Neuroreport, 19 (1), pp. 37–41, 2008. @article{Alahyane2008b, title = {Spatial transfer of adaptation of scanning voluntary saccades in humans}, author = {Nadia Alahyane and Anne-Dominique Devauchelle and Roméo Salemme and Denis Pélisson}, doi = {10.1097/WNR.0b013e3282f2a5f2}, year = {2008}, date = {2008-01-01}, journal = {Neuroreport}, volume = {19}, number = {1}, pages = {37--41}, abstract = {The properties and neural substrates of the adaptive mechanisms that maintain over time the accuracy of voluntary, internally triggered saccades are still poorly understood. Here, we used transfer tests to evaluate the spatial properties of adaptation of scanning voluntary saccades. We found that an adaptive reduction of the size of a horizontal rightward 7 degrees saccade transferred to other saccades of a wide range of amplitudes and directions. This transfer decreased as tested saccades increasingly differed in amplitude or direction from the trained saccade, being null for vertical and leftward saccades. Voluntary saccade adaptation thus presents bounded, but large adaptation fields, suggesting that at least part of the underlying neural substrate encodes saccades as vectors.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The properties and neural substrates of the adaptive mechanisms that maintain over time the accuracy of voluntary, internally triggered saccades are still poorly understood. Here, we used transfer tests to evaluate the spatial properties of adaptation of scanning voluntary saccades. We found that an adaptive reduction of the size of a horizontal rightward 7 degrees saccade transferred to other saccades of a wide range of amplitudes and directions. This transfer decreased as tested saccades increasingly differed in amplitude or direction from the trained saccade, being null for vertical and leftward saccades. Voluntary saccade adaptation thus presents bounded, but large adaptation fields, suggesting that at least part of the underlying neural substrate encodes saccades as vectors. |
Nadia Alahyane; Christelle Lemoine-Lardennois; Coline Tailhefer; Thérèse Collins; Jacqueline Fagard; Karine Doré-Mazars Development and learning of saccadic eye movements in 7- to 42-month-old children Journal Article Journal of Vision, 16 (1), pp. 1–12, 2016. @article{Alahyane2016, title = {Development and learning of saccadic eye movements in 7- to 42-month-old children}, author = {Nadia Alahyane and Christelle Lemoine-Lardennois and Coline Tailhefer and Thér{è}se Collins and Jacqueline Fagard and Karine Doré-Mazars}, doi = {10.1167/16.1.6}, year = {2016}, date = {2016-01-01}, journal = {Journal of Vision}, volume = {16}, number = {1}, pages = {1--12}, abstract = {From birth, infants move their eyes to explore their environment, interact with it, and progressively develop a multitude of motor and cognitive abilities. The characteristics and development of oculomotor control in early childhood remain poorly understood today. Here, we examined reaction time and amplitude of saccadic eye movements in 93 7- to 42-month-old children while they oriented toward visual animated cartoon characters appearing at unpredictable locations on a computer screen over 140 trials. Results revealed that saccade performance is immature in children compared to a group of adults: Saccade reaction times were longer, and saccade amplitude relative to target location (10° eccentricity) was shorter. Results also indicated that performance is flexible in children. Although saccade reaction time decreased as age increased, suggesting developmental improvements in saccade control, saccade amplitude gradually improved over trials. Moreover, similar to adults, children were able to modify saccade amplitude based on the visual error made in the previous trial. This second set of results suggests that short visual experience and/or rapid sensorimotor learning are functional in children and can also affect saccade performance.}, keywords = {}, pubstate = {published}, tppubtype = {article} } From birth, infants move their eyes to explore their environment, interact with it, and progressively develop a multitude of motor and cognitive abilities. The characteristics and development of oculomotor control in early childhood remain poorly understood today. Here, we examined reaction time and amplitude of saccadic eye movements in 93 7- to 42-month-old children while they oriented toward visual animated cartoon characters appearing at unpredictable locations on a computer screen over 140 trials. Results revealed that saccade performance is immature in children compared to a group of adults: Saccade reaction times were longer, and saccade amplitude relative to target location (10° eccentricity) was shorter. Results also indicated that performance is flexible in children. Although saccade reaction time decreased as age increased, suggesting developmental improvements in saccade control, saccade amplitude gradually improved over trials. Moreover, similar to adults, children were able to modify saccade amplitude based on the visual error made in the previous trial. This second set of results suggests that short visual experience and/or rapid sensorimotor learning are functional in children and can also affect saccade performance. |
Noor Z Al Dahhan; George K Georgiou; Rickie Hung; Douglas Munoz; Rauno Parrila; John R Kirby Eye movements of university students with and without reading difficulties during naming speed tasks Journal Article Annals of Dyslexia, 64 (2), pp. 137–150, 2014. @article{AlDahhan2014, title = {Eye movements of university students with and without reading difficulties during naming speed tasks}, author = {Noor Z {Al Dahhan} and George K Georgiou and Rickie Hung and Douglas Munoz and Rauno Parrila and John R Kirby}, doi = {10.1007/s11881-013-0090-z}, year = {2014}, date = {2014-01-01}, journal = {Annals of Dyslexia}, volume = {64}, number = {2}, pages = {137--150}, abstract = {Although naming speed (NS) has been shown to predict reading into adulthood and differentiate between adult dyslexics and controls, the question remains why NS is related to reading. To address this question, eye movement methodology was combined with three letter NS tasks (the original letter NS task by Denckla & Rudel, Cortex 10:186-202, 1974, and two more developed by Compton, The Journal of Special Education 37:81-94, 2003, with increased phonological or visual similarity of the letters). Twenty undergraduate students with reading difficulties (RD) and 27 without (NRD) were tested on letter NS tasks (eye movements were recorded during the NS tasks), phonological processing, and reading fluency. The results indicated first that the RD group was slower than the NRD group on all NS tasks with no differences between the NS tasks. In addition, the NRD group had shorter fixation durations, longer saccades, and fewer saccades and fixations than the RD group. Fixation duration and fixation count were significant predictors of reading fluency even after controlling for phonological processing measures. Taken together, these findings suggest that the NS-reading relationship is due to two factors: less able readers require more time to acquire stimulus information during fixation and they make more saccades.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Although naming speed (NS) has been shown to predict reading into adulthood and differentiate between adult dyslexics and controls, the question remains why NS is related to reading. To address this question, eye movement methodology was combined with three letter NS tasks (the original letter NS task by Denckla & Rudel, Cortex 10:186-202, 1974, and two more developed by Compton, The Journal of Special Education 37:81-94, 2003, with increased phonological or visual similarity of the letters). Twenty undergraduate students with reading difficulties (RD) and 27 without (NRD) were tested on letter NS tasks (eye movements were recorded during the NS tasks), phonological processing, and reading fluency. The results indicated first that the RD group was slower than the NRD group on all NS tasks with no differences between the NS tasks. In addition, the NRD group had shorter fixation durations, longer saccades, and fewer saccades and fixations than the RD group. Fixation duration and fixation count were significant predictors of reading fluency even after controlling for phonological processing measures. Taken together, these findings suggest that the NS-reading relationship is due to two factors: less able readers require more time to acquire stimulus information during fixation and they make more saccades. |
Noor Z Al Dahhan; John R Kirby; Donald C Brien; Douglas P Munoz Eye movements and articulations during a letter naming speed task: Children with and without Dyslexia Journal Article Journal of Learning Disabilities, 50 (3), pp. 275–285, 2017. @article{AlDahhan2017, title = {Eye movements and articulations during a letter naming speed task: Children with and without Dyslexia}, author = {Noor Z {Al Dahhan} and John R Kirby and Donald C Brien and Douglas P Munoz}, doi = {10.1177/0022219415618502}, year = {2017}, date = {2017-01-01}, journal = {Journal of Learning Disabilities}, volume = {50}, number = {3}, pages = {275--285}, abstract = {Abstract Naming speed (NS) refers to how quickly and accurately participants name a set of familiar stimuli (e.g., letters). NS is an established predictor of reading ability, but controversy remains over why it is related to reading. We used three techniques (stimulus manipulations to emphasize phonological and/or visual aspects, decomposition of NS times into pause and articulation components, and analysis of eye movements during task performance) with three groups of participants (children with dyslexia, ages 9–10; chronological-age [CA] controls, ages 9–10; reading-level [RL] controls, ages 6–7) to examine NS and the NS–reading relationship. Results indicated (a) for all groups, increasing visual similarity of the letters decreased letter naming efficiency and increased naming errors, saccades, regressions (rapid eye movements back to letters already fixated), pause times, and fixation durations; (b) children with dyslexia performed like RL controls and were less efficient, had longer articulation times, pause times, fixation durations, and made more errors and regressions than CA controls; and (c) pause time and fixation duration were the most powerful predictors of reading. We conclude that NS is related to reading via fixation durations and pause times: Longer fixation durations and pause times reflect the greater amount of time needed to acquire visual/orthographic information from stimuli and prepare the correct response.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Abstract Naming speed (NS) refers to how quickly and accurately participants name a set of familiar stimuli (e.g., letters). NS is an established predictor of reading ability, but controversy remains over why it is related to reading. We used three techniques (stimulus manipulations to emphasize phonological and/or visual aspects, decomposition of NS times into pause and articulation components, and analysis of eye movements during task performance) with three groups of participants (children with dyslexia, ages 9–10; chronological-age [CA] controls, ages 9–10; reading-level [RL] controls, ages 6–7) to examine NS and the NS–reading relationship. Results indicated (a) for all groups, increasing visual similarity of the letters decreased letter naming efficiency and increased naming errors, saccades, regressions (rapid eye movements back to letters already fixated), pause times, and fixation durations; (b) children with dyslexia performed like RL controls and were less efficient, had longer articulation times, pause times, fixation durations, and made more errors and regressions than CA controls; and (c) pause time and fixation duration were the most powerful predictors of reading. We conclude that NS is related to reading via fixation durations and pause times: Longer fixation durations and pause times reflect the greater amount of time needed to acquire visual/orthographic information from stimuli and prepare the correct response. |
Ava-Ann Allman; Ulrich Ettinger; Ridha Joober; Gillian A O'Driscoll Effects of methylphenidate on basic and higher-order oculomotor functions Journal Article Journal of Psychopharmacology, 26 (11), pp. 1471–1479, 2012. @article{Allman2012, title = {Effects of methylphenidate on basic and higher-order oculomotor functions}, author = {Ava-Ann Allman and Ulrich Ettinger and Ridha Joober and Gillian A O'Driscoll}, doi = {10.1177/0269881112446531}, year = {2012}, date = {2012-01-01}, journal = {Journal of Psychopharmacology}, volume = {26}, number = {11}, pages = {1471--1479}, abstract = {Eye movements are sensitive indicators of pharmacological effects on sensorimotor and cognitive processing. Methylphenidate (MPH) is one of the most prescribed medications in psychiatry. It is increasingly used as a cognitive enhancer by healthy individuals. However, little is known of its effect on healthy cognition. Here we used oculomotor tests to evaluate the effects of MPH on basic oculomotor and executive functions. Twenty-nine males were given 20mg of MPH orally in a double-blind placebo-controlled crossover design. Participants performed visually-guided saccades, sinusoidal smooth pursuit, predictive saccades and antisaccades one hour post-capsule administration. Heart rate and blood pressure were assessed prior to capsule administration, and again before and after task performance. Visually-guided saccade latency decreased with MPH (ptextless0.004). Smooth pursuit gain increased on MPH (ptextless0.001) and number of saccades during pursuit decreased (ptextless0.001). Proportion of predictive saccades increased on MPH (ptextless0.004), specifically in conditions with predictable timing. Peak velocity of predictive saccades increased with MPH (ptextless0.01). Antisaccade errors and latency were unaffected. Physiological variables were also unaffected. The effects on visually-guided saccade latency and peak velocity are consistent with MPH effects on dopamine in basal ganglia. The improvements in predictive saccade conditions and smooth pursuit suggest effects on timing functions.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Eye movements are sensitive indicators of pharmacological effects on sensorimotor and cognitive processing. Methylphenidate (MPH) is one of the most prescribed medications in psychiatry. It is increasingly used as a cognitive enhancer by healthy individuals. However, little is known of its effect on healthy cognition. Here we used oculomotor tests to evaluate the effects of MPH on basic oculomotor and executive functions. Twenty-nine males were given 20mg of MPH orally in a double-blind placebo-controlled crossover design. Participants performed visually-guided saccades, sinusoidal smooth pursuit, predictive saccades and antisaccades one hour post-capsule administration. Heart rate and blood pressure were assessed prior to capsule administration, and again before and after task performance. Visually-guided saccade latency decreased with MPH (ptextless0.004). Smooth pursuit gain increased on MPH (ptextless0.001) and number of saccades during pursuit decreased (ptextless0.001). Proportion of predictive saccades increased on MPH (ptextless0.004), specifically in conditions with predictable timing. Peak velocity of predictive saccades increased with MPH (ptextless0.01). Antisaccade errors and latency were unaffected. Physiological variables were also unaffected. The effects on visually-guided saccade latency and peak velocity are consistent with MPH effects on dopamine in basal ganglia. The improvements in predictive saccade conditions and smooth pursuit suggest effects on timing functions. |
Roy Amit; Dekel Abeles; Izhar Bar-Gad; Shlomit Yuval-Greenberg Temporal dynamics of saccades explained by a self-paced process Journal Article Scientific Reports, 7 (1), pp. 1–15, 2017. @article{Amit2017, title = {Temporal dynamics of saccades explained by a self-paced process}, author = {Roy Amit and Dekel Abeles and Izhar Bar-Gad and Shlomit Yuval-Greenberg}, doi = {10.1038/s41598-017-00881-7}, year = {2017}, date = {2017-12-01}, journal = {Scientific Reports}, volume = {7}, number = {1}, pages = {1--15}, publisher = {Springer US}, abstract = {Sensory organs are thought to sample the environment rhythmically thereby providing periodic perceptual input. Whisking and sniffing are governed by oscillators which impose rhythms on the motor-control of sensory acquisition and consequently on sensory input. Saccadic eye movements are the main visual sampling mechanism in primates, and were suggested to constitute part of such a rhythmic exploration system. In this study we characterized saccadic rhythmicity, and examined whether it is consistent with autonomous oscillatory generator or with self-paced generation. Eye movements were tracked while observers were either free-viewing a movie or fixating a static stimulus. We inspected the temporal dynamics of exploratory and fixational saccades and quantified their first-order and high-order dependencies. Data were analyzed using methods derived from spike-train analysis, and tested against mathematical models and simulations. The findings show that saccade timings are explained by first-order dependencies, specifically by their refractory period. Saccade-timings are inconsistent with an autonomous pace-maker but are consistent with a “self-paced” generator, where each saccade is a link in a chain of neural processes that depend on the outcome of the saccade itself. We propose a mathematical model parsimoniously capturing various facets of saccade-timings, and suggest a possible neural mechanism producing the observed dynamics.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Sensory organs are thought to sample the environment rhythmically thereby providing periodic perceptual input. Whisking and sniffing are governed by oscillators which impose rhythms on the motor-control of sensory acquisition and consequently on sensory input. Saccadic eye movements are the main visual sampling mechanism in primates, and were suggested to constitute part of such a rhythmic exploration system. In this study we characterized saccadic rhythmicity, and examined whether it is consistent with autonomous oscillatory generator or with self-paced generation. Eye movements were tracked while observers were either free-viewing a movie or fixating a static stimulus. We inspected the temporal dynamics of exploratory and fixational saccades and quantified their first-order and high-order dependencies. Data were analyzed using methods derived from spike-train analysis, and tested against mathematical models and simulations. The findings show that saccade timings are explained by first-order dependencies, specifically by their refractory period. Saccade-timings are inconsistent with an autonomous pace-maker but are consistent with a “self-paced” generator, where each saccade is a link in a chain of neural processes that depend on the outcome of the saccade itself. We propose a mathematical model parsimoniously capturing various facets of saccade-timings, and suggest a possible neural mechanism producing the observed dynamics. |
Richard Amlôt; Robin Walker; Jon Driver; Charles Spence Multimodal visual–somatosensory integration in saccade generation Journal Article Neuropsychologia, 41 (1), pp. 1–15, 2003. @article{Amlot2003, title = {Multimodal visual–somatosensory integration in saccade generation}, author = {Richard Aml{ô}t and Robin Walker and Jon Driver and Charles Spence}, doi = {10.1016/S0028-3932(02)00139-2}, year = {2003}, date = {2003-01-01}, journal = {Neuropsychologia}, volume = {41}, number = {1}, pages = {1--15}, abstract = {Neurophysiological studies have demonstrated multisensory interaction effects in the neural structures involved in saccade generation when visual, auditory or somatosensory stimuli are presented bimodally. Visual–auditory interaction effects have been demonstrated in numerous behavioural studies of saccades but little is known about interaction effects involving somatosensory stimuli. The present study examined visual–somatosensory interaction effects on saccade generation using a multisensory paradigm, whereby task-irrelevant distractors appeared spatially-coincident with, or remote from the designated saccade target. Somatosensory distractors reduced the latency of saccades when presented before the visual target and the greatest facilitation effectwas observed with spatially-coincident stimuli.Visual distractors spatially-coincident with a somatosensory target reduced latency (and increased peak velocity) when presented before and after the target.Visual distractors contralateral to somatosensory targets increased saccade latency and produced high error rates of saccades made to the distractor. The high error rates and latencymodulation with visual distractors is consistent with a bias for visual stimuli in the saccadic system. In the visual target condition, saccade latency was modulated by a somatosensory distractor that was entirely task-irrelevant and this effect was always greatest with spatially-coincident distractors. The multisensory distractor effects are discussed in terms of saccades being programmed to the non-target modality, the early triggering of a non-spatial saccade ‘when' signal, and multisensory neuronal enhancement effects.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Neurophysiological studies have demonstrated multisensory interaction effects in the neural structures involved in saccade generation when visual, auditory or somatosensory stimuli are presented bimodally. Visual–auditory interaction effects have been demonstrated in numerous behavioural studies of saccades but little is known about interaction effects involving somatosensory stimuli. The present study examined visual–somatosensory interaction effects on saccade generation using a multisensory paradigm, whereby task-irrelevant distractors appeared spatially-coincident with, or remote from the designated saccade target. Somatosensory distractors reduced the latency of saccades when presented before the visual target and the greatest facilitation effectwas observed with spatially-coincident stimuli.Visual distractors spatially-coincident with a somatosensory target reduced latency (and increased peak velocity) when presented before and after the target.Visual distractors contralateral to somatosensory targets increased saccade latency and produced high error rates of saccades made to the distractor. The high error rates and latencymodulation with visual distractors is consistent with a bias for visual stimuli in the saccadic system. In the visual target condition, saccade latency was modulated by a somatosensory distractor that was entirely task-irrelevant and this effect was always greatest with spatially-coincident distractors. The multisensory distractor effects are discussed in terms of saccades being programmed to the non-target modality, the early triggering of a non-spatial saccade ‘when' signal, and multisensory neuronal enhancement effects. |
Tatiana A Amor; Saulo D S Reis; Daniel Campos; Hans J Herrmann; José S Andrade Persistence in eye movement during visual search Journal Article Scientific Reports, 6 , pp. 1–12, 2016. @article{Amor2016, title = {Persistence in eye movement during visual search}, author = {Tatiana A Amor and Saulo D S Reis and Daniel Campos and Hans J Herrmann and José S Andrade}, doi = {10.1038/srep20815}, year = {2016}, date = {2016-01-01}, journal = {Scientific Reports}, volume = {6}, pages = {1--12}, publisher = {Nature Publishing Group}, abstract = {As any cognitive task, visual search involves a number of underlying processes that cannot be directly observed and measured. In this way, the movement of the eyes certainly represents the most explicit and closest connection we can get to the inner mechanisms governing this cognitive activity. Here we show that the process of eye movement during visual search, consisting of sequences of fixations intercalated by saccades, exhibits distinctive persistent behaviors. Initially, by focusing on saccadic directions and intersaccadic angles, we disclose that the probability distributions of these measures show a clear preference of participants towards a reading-like mechanism (geometrical persistence), whose features and potential advantages for searching/foraging are discussed. We then perform a Multifractal Detrended Fluctuation Analysis (MF-DFA) over the time series of jump magnitudes in the eye trajectory and find that it exhibits a typical multifractal behavior arising from the sequential combination of saccades and fixations. By inspecting the time series composed of only fixational movements, our results reveal instead a monofractal behavior with a Hurst exponent , which indicates the presence of long-range power-law positive correlations (statistical persistence). We expect that our methodological approach can be adopted as a way to understand persistence and strategy-planning during visual search.}, keywords = {}, pubstate = {published}, tppubtype = {article} } As any cognitive task, visual search involves a number of underlying processes that cannot be directly observed and measured. In this way, the movement of the eyes certainly represents the most explicit and closest connection we can get to the inner mechanisms governing this cognitive activity. Here we show that the process of eye movement during visual search, consisting of sequences of fixations intercalated by saccades, exhibits distinctive persistent behaviors. Initially, by focusing on saccadic directions and intersaccadic angles, we disclose that the probability distributions of these measures show a clear preference of participants towards a reading-like mechanism (geometrical persistence), whose features and potential advantages for searching/foraging are discussed. We then perform a Multifractal Detrended Fluctuation Analysis (MF-DFA) over the time series of jump magnitudes in the eye trajectory and find that it exhibits a typical multifractal behavior arising from the sequential combination of saccades and fixations. By inspecting the time series composed of only fixational movements, our results reveal instead a monofractal behavior with a Hurst exponent , which indicates the presence of long-range power-law positive correlations (statistical persistence). We expect that our methodological approach can be adopted as a way to understand persistence and strategy-planning during visual search. |
Nicola C Anderson; Eduard Ort; Wouter Kruijne; Martijn Meeter; Mieke Donk It depends on when you look at it: Salience influences eye movements in natural scene viewing and search early in time Journal Article Journal of Vision, 15 (5), pp. 1–22, 2015. @article{Anderson2015b, title = {It depends on when you look at it: Salience influences eye movements in natural scene viewing and search early in time}, author = {Nicola C Anderson and Eduard Ort and Wouter Kruijne and Martijn Meeter and Mieke Donk}, doi = {10.1167/15.5.9.doi}, year = {2015}, date = {2015-01-01}, journal = {Journal of Vision}, volume = {15}, number = {5}, pages = {1--22}, abstract = {It is generally accepted that salience affects eye movements in simple artificially created search displays. However, no such consensus exists for eye movements in natural scenes, with several reports arguing that it is mostly high-level cognitive factors that control oculomotor behavior in natural scenes. Here, we manipulate the salience distribution across images by decreasing or increasing the contrast in a gradient across the image. We recorded eye movements in an encoding task (Experiment 1) and a visual search task (Experiment 2) and analyzed the relationship between the latency of fixations and subsequent saccade targeting throughout scene viewing. We find that short-latency first saccades are more likely to land on a region of the image with high salience than long-latency and subsequent saccades in both the encoding and visual search tasks. This implies that salience indeed influences oculomotor behavior in natural scenes, albeit on a different timescale than previously reported. We discuss our findings in relation to current theories of saccade control in natural scenes.}, keywords = {}, pubstate = {published}, tppubtype = {article} } It is generally accepted that salience affects eye movements in simple artificially created search displays. However, no such consensus exists for eye movements in natural scenes, with several reports arguing that it is mostly high-level cognitive factors that control oculomotor behavior in natural scenes. Here, we manipulate the salience distribution across images by decreasing or increasing the contrast in a gradient across the image. We recorded eye movements in an encoding task (Experiment 1) and a visual search task (Experiment 2) and analyzed the relationship between the latency of fixations and subsequent saccade targeting throughout scene viewing. We find that short-latency first saccades are more likely to land on a region of the image with high salience than long-latency and subsequent saccades in both the encoding and visual search tasks. This implies that salience indeed influences oculomotor behavior in natural scenes, albeit on a different timescale than previously reported. We discuss our findings in relation to current theories of saccade control in natural scenes. |
Elaine J Anderson; Marc S Tibber; Sam D Schwarzkopf; Sukhwinder S Shergill; Emilio Fernandez-Egea; Geraint Rees; Steven C Dakin Visual population receptive fields in people with schizophrenia have reduced inhibitory surrounds Journal Article Journal of Neuroscience, 37 (6), pp. 1546–1556, 2017. @article{Anderson2017, title = {Visual population receptive fields in people with schizophrenia have reduced inhibitory surrounds}, author = {Elaine J Anderson and Marc S Tibber and Sam D Schwarzkopf and Sukhwinder S Shergill and Emilio Fernandez-Egea and Geraint Rees and Steven C Dakin}, doi = {10.1523/JNEUROSCI.3620-15.2016}, year = {2017}, date = {2017-01-01}, journal = {Journal of Neuroscience}, volume = {37}, number = {6}, pages = {1546--1556}, abstract = {People with schizophrenia (SZ) experience abnormal visual perception on a range of visual tasks, which have been linked to abnormal synaptic transmission and an imbalance between cortical excitation and inhibition. However, differences in the underlying architecture of visual cortex neurons, which might explain these visual anomalies, have yet to be reportedin vivoHere, we probed the neural basis of these deficits using fMRI and population receptive field (pRF) mapping to infer properties of visually responsive neurons in people with SZ. We employed a difference-of-Gaussian model to capture the center-surround configuration of the pRF, providing critical information about the spatial scale of the pRFs inhibitory surround. Our analysis reveals that SZ is associated with reduced pRF size in early retinotopic visual cortex, as well as a reduction in size and depth of the inhibitory surround in V1, V2, and V4. We consider how reduced inhibition might explain the diverse range of visual deficits reported in SZ.}, keywords = {}, pubstate = {published}, tppubtype = {article} } People with schizophrenia (SZ) experience abnormal visual perception on a range of visual tasks, which have been linked to abnormal synaptic transmission and an imbalance between cortical excitation and inhibition. However, differences in the underlying architecture of visual cortex neurons, which might explain these visual anomalies, have yet to be reportedin vivoHere, we probed the neural basis of these deficits using fMRI and population receptive field (pRF) mapping to infer properties of visually responsive neurons in people with SZ. We employed a difference-of-Gaussian model to capture the center-surround configuration of the pRF, providing critical information about the spatial scale of the pRFs inhibitory surround. Our analysis reveals that SZ is associated with reduced pRF size in early retinotopic visual cortex, as well as a reduction in size and depth of the inhibitory surround in V1, V2, and V4. We consider how reduced inhibition might explain the diverse range of visual deficits reported in SZ. |
Neil K Archibald; Samuel B Hutton; Michael P Clarke; Urs P Mosimann; David J Burn Visual exploration in Parkinson's disease and Parkinson's disease dementia Journal Article Brain, 136 (3), pp. 739–750, 2013. @article{Archibald2013, title = {Visual exploration in Parkinson's disease and Parkinson's disease dementia}, author = {Neil K Archibald and Samuel B Hutton and Michael P Clarke and Urs P Mosimann and David J Burn}, doi = {10.1093/brain/awt005}, year = {2013}, date = {2013-01-01}, journal = {Brain}, volume = {136}, number = {3}, pages = {739--750}, abstract = {Parkinson's disease, typically thought of as a movement disorder, is increasingly recognized as causing cognitive impairment and dementia. Eye movement abnormalities are also described, including impairment of rapid eye movements (saccades) and the fixations interspersed between them. Such movements are under the influence of cortical and subcortical networks commonly targeted by the neurodegeneration seen in Parkinson's disease and, as such, may provide a marker for cognitive decline. This study examined the error rates and visual exploration strategies of subjects with Parkinson's disease, with and without cognitive impairment, whilst performing a battery of visuo-cognitive tasks. Error rates were significantly higher in those Parkinson's disease groups with either mild cognitive impairment (P = 0.001) or dementia (P textless 0.001), than in cognitively normal subjects with Parkinson's disease. When compared with cognitively normal subjects with Parkinson's disease, exploration strategy, as measured by a number of eye tracking variables, was least efficient in the dementia group but was also affected in those subjects with Parkinson's disease with mild cognitive impairment. When compared with control subjects and cognitively normal subjects with Parkinson's disease, saccade amplitudes were significantly reduced in the groups with mild cognitive impairment or dementia. Fixation duration was longer in all Parkinson's disease groups compared with healthy control subjects but was longest for cognitively impaired Parkinson's disease groups. The strongest predictor of average fixation duration was disease severity. Analysing only data from the most complex task, with the highest error rates, both cognitive impairment and disease severity contributed to a predictive model for fixation duration F(2,76) = 12.52, P 0.001, but medication dose did not (r = 0.18}, keywords = {}, pubstate = {published}, tppubtype = {article} } Parkinson's disease, typically thought of as a movement disorder, is increasingly recognized as causing cognitive impairment and dementia. Eye movement abnormalities are also described, including impairment of rapid eye movements (saccades) and the fixations interspersed between them. Such movements are under the influence of cortical and subcortical networks commonly targeted by the neurodegeneration seen in Parkinson's disease and, as such, may provide a marker for cognitive decline. This study examined the error rates and visual exploration strategies of subjects with Parkinson's disease, with and without cognitive impairment, whilst performing a battery of visuo-cognitive tasks. Error rates were significantly higher in those Parkinson's disease groups with either mild cognitive impairment (P = 0.001) or dementia (P textless 0.001), than in cognitively normal subjects with Parkinson's disease. When compared with cognitively normal subjects with Parkinson's disease, exploration strategy, as measured by a number of eye tracking variables, was least efficient in the dementia group but was also affected in those subjects with Parkinson's disease with mild cognitive impairment. When compared with control subjects and cognitively normal subjects with Parkinson's disease, saccade amplitudes were significantly reduced in the groups with mild cognitive impairment or dementia. Fixation duration was longer in all Parkinson's disease groups compared with healthy control subjects but was longest for cognitively impaired Parkinson's disease groups. The strongest predictor of average fixation duration was disease severity. Analysing only data from the most complex task, with the highest error rates, both cognitive impairment and disease severity contributed to a predictive model for fixation duration F(2,76) = 12.52, P 0.001, but medication dose did not (r = 0.18 |
Kiki Arkesteijn; Jeroen B J Smeets; Mieke Donk; Artem V Belopolsky Target-distractor competition cannot be resolved across a saccade Journal Article Scientific Reports, 8 (1), pp. 1–10, 2018. @article{Arkesteijn2018, title = {Target-distractor competition cannot be resolved across a saccade}, author = {Kiki Arkesteijn and Jeroen B J Smeets and Mieke Donk and Artem V Belopolsky}, doi = {10.1038/s41598-018-34120-4}, year = {2018}, date = {2018-01-01}, journal = {Scientific Reports}, volume = {8}, number = {1}, pages = {1--10}, publisher = {Springer US}, abstract = {When a distractor is presented in close spatial proximity to a target, a saccade tends to land in between the two objects rather than on the target. This robust phenomenon (also referred to as the global efect) is thought to refect unresolved competition between target and distractor. It is unclear whether this landing bias persists across saccades since a saccade displaces the retinotopic representations of target and distractor. In the present study participants made successive saccades towards two saccadic targets which were presented simultaneously with an irrelevant distractor in close proximity to the second saccade target. The second saccade was either visually-guided or memory-guided. For the memory-guided trials, the second saccade showed a landing bias towards the location of the distractor, despite the disappearance of the distractor after the frst saccade. In contrast, for the visually-guided trials, the bias was corrected and the landing bias was eliminated, even for saccades with the shortest intersaccadic intervals. This suggests that the biased saccade plan was remapped across the frst saccade. Therefore, we conclude that the target-distractor competition was not resolved across a saccade, but can be resolved based on visual information that is available after a saccade.}, keywords = {}, pubstate = {published}, tppubtype = {article} } When a distractor is presented in close spatial proximity to a target, a saccade tends to land in between the two objects rather than on the target. This robust phenomenon (also referred to as the global efect) is thought to refect unresolved competition between target and distractor. It is unclear whether this landing bias persists across saccades since a saccade displaces the retinotopic representations of target and distractor. In the present study participants made successive saccades towards two saccadic targets which were presented simultaneously with an irrelevant distractor in close proximity to the second saccade target. The second saccade was either visually-guided or memory-guided. For the memory-guided trials, the second saccade showed a landing bias towards the location of the distractor, despite the disappearance of the distractor after the frst saccade. In contrast, for the visually-guided trials, the bias was corrected and the landing bias was eliminated, even for saccades with the shortest intersaccadic intervals. This suggests that the biased saccade plan was remapped across the frst saccade. Therefore, we conclude that the target-distractor competition was not resolved across a saccade, but can be resolved based on visual information that is available after a saccade. |
I T Armstrong; Douglas P Munoz Inhibitory control of eye movements during oculomotor countermanding in adults with attention-deficit hyperactivity disorder Journal Article Experimental Brain Research, 152 (4), pp. 444–452, 2003. @article{Armstrong2003a, title = {Inhibitory control of eye movements during oculomotor countermanding in adults with attention-deficit hyperactivity disorder}, author = {I T Armstrong and Douglas P Munoz}, doi = {10.1007/s00221-003-1569-3}, year = {2003}, date = {2003-01-01}, journal = {Experimental Brain Research}, volume = {152}, number = {4}, pages = {444--452}, abstract = {Children with attention-deficit hyperactivity disorder (ADHD) are impulsive, and that impulsiveness can be measured using a countermanding task. Although the overt behaviors of ADHD attenuate with age, it is not clear how well impulsiveness is controlled in adults with ADHD. We tested ADHD adults with an oculomotor countermanding task. The task included two conditions: on 75% of the trials, participants viewed a central fixation marker and then looked to an eccentric target that appeared simultaneous with the disappearance of the fixation marker; on 25% of the trials, a signal was presented at variable delays after target appearance. The signal instructed subjects to stop, or countermand, an eye movement to the target. A correct movement in this case would be to hold gaze at the central fixation location. We expected ADHD participants to be impulsive in their countermanding performance. Additionally, we expected that a visual stop signal at the central fixation location would assist oculomotor countermanding because the signal is presented in the "stop" location, at fixation. To test whether a central stop signal positively biased countermanding, we used a three types of stop signal to instruct the stop: a central visual marker, a peripheral visual signal, and a non-localized sound. All subjects performed best with the central visual stop signal. Subjects with ADHD were less able to countermand eye movements and were influenced more negatively by the non-central signals. Oculomotor countermanding may be useful for quantifying impulsive dysfunction in adults with ADHD especially if a non-central stop signal is applied.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Children with attention-deficit hyperactivity disorder (ADHD) are impulsive, and that impulsiveness can be measured using a countermanding task. Although the overt behaviors of ADHD attenuate with age, it is not clear how well impulsiveness is controlled in adults with ADHD. We tested ADHD adults with an oculomotor countermanding task. The task included two conditions: on 75% of the trials, participants viewed a central fixation marker and then looked to an eccentric target that appeared simultaneous with the disappearance of the fixation marker; on 25% of the trials, a signal was presented at variable delays after target appearance. The signal instructed subjects to stop, or countermand, an eye movement to the target. A correct movement in this case would be to hold gaze at the central fixation location. We expected ADHD participants to be impulsive in their countermanding performance. Additionally, we expected that a visual stop signal at the central fixation location would assist oculomotor countermanding because the signal is presented in the "stop" location, at fixation. To test whether a central stop signal positively biased countermanding, we used a three types of stop signal to instruct the stop: a central visual marker, a peripheral visual signal, and a non-localized sound. All subjects performed best with the central visual stop signal. Subjects with ADHD were less able to countermand eye movements and were influenced more negatively by the non-central signals. Oculomotor countermanding may be useful for quantifying impulsive dysfunction in adults with ADHD especially if a non-central stop signal is applied. |
I T Armstrong; Douglas P Munoz Attentional blink in adults with attention-deficit hyperactivity disorder: Influence of eye movements Journal Article Experimental Brain Research, 152 (2), pp. 243–250, 2003. @article{Armstrong2003b, title = {Attentional blink in adults with attention-deficit hyperactivity disorder: Influence of eye movements}, author = {I T Armstrong and Douglas P Munoz}, doi = {10.1007/s00221-003-1535-0}, year = {2003}, date = {2003-01-01}, journal = {Experimental Brain Research}, volume = {152}, number = {2}, pages = {243--250}, abstract = {The attentional blink paradigm tests attention by overloading it: a list of stimuli is presented very rapidly one after another at the same location on a computer screen, each item overwriting the last, and participants monitor the list using two criteria [e.g. detect the target (red letter) and identify the probe (letter p)]. If the interval between the target and the probe is greater than about 500 ms, both are usually reported correctly, but, when the interval between the target and the probe is within 200-500 ms, report of the probe declines. This decline is the attentional blink, an interval of time when attention is supposedly switching from the first criterion to the second. The attentional blink paradigm should be difficult to perform correctly without vigilantly attending to the rapidly presented list. Vigilance tasks are often used to assess attention-deficit hyperactivity disorder (ADHD). Symptoms of the disorder include hyperactivity and attentional dysfunction; however, some people with ADHD also have difficulty maintaining gaze at a fixed location. We tested 15 adults with ADHD and their age- and sex-matched controls, measuring accuracy and gaze stability during the attentional blink task. ADHD participants reported fewer targets and probes, took longer to recover from the attentional blink, made more eye movements, and made identification errors consistent with non-perception of the letter list. In contrast, errors made by control participants were consistent with guessing (i.e., report of a letter immediately preceding or succeeding the correct letter). Excessive eye movements result in poorer performance for all participants; however, error patterns confirm that the weak performance of ADHD participants may be related to gaze instability as well as to attentional dysfunction.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The attentional blink paradigm tests attention by overloading it: a list of stimuli is presented very rapidly one after another at the same location on a computer screen, each item overwriting the last, and participants monitor the list using two criteria [e.g. detect the target (red letter) and identify the probe (letter p)]. If the interval between the target and the probe is greater than about 500 ms, both are usually reported correctly, but, when the interval between the target and the probe is within 200-500 ms, report of the probe declines. This decline is the attentional blink, an interval of time when attention is supposedly switching from the first criterion to the second. The attentional blink paradigm should be difficult to perform correctly without vigilantly attending to the rapidly presented list. Vigilance tasks are often used to assess attention-deficit hyperactivity disorder (ADHD). Symptoms of the disorder include hyperactivity and attentional dysfunction; however, some people with ADHD also have difficulty maintaining gaze at a fixed location. We tested 15 adults with ADHD and their age- and sex-matched controls, measuring accuracy and gaze stability during the attentional blink task. ADHD participants reported fewer targets and probes, took longer to recover from the attentional blink, made more eye movements, and made identification errors consistent with non-perception of the letter list. In contrast, errors made by control participants were consistent with guessing (i.e., report of a letter immediately preceding or succeeding the correct letter). Excessive eye movements result in poorer performance for all participants; however, error patterns confirm that the weak performance of ADHD participants may be related to gaze instability as well as to attentional dysfunction. |
Daniel S Asfaw; Pete R Jones; Nicholas D Smith; David P Crabb Data on eye movements in people with glaucoma and peers with normal vision Journal Article Data in Brief, 19 , pp. 1266–1273, 2018. @article{Asfaw2018, title = {Data on eye movements in people with glaucoma and peers with normal vision}, author = {Daniel S Asfaw and Pete R Jones and Nicholas D Smith and David P Crabb}, year = {2018}, date = {2018-08-01}, journal = {Data in Brief}, volume = {19}, pages = {1266--1273}, publisher = {Elsevier}, abstract = {Eye movements of glaucoma patients have been shown to differ from age-similar control groups when performing everyday tasks, such as reading (Burton et al., 2012; Smith et al., 2014) [1,2], visual search (Smith et al., 2012) [3], face recognition (Glen et al., 2013) [4], driving, and viewing static images (Smith et al., 2012) [5]. Described here is the dataset from a recent publication in which we compared the eye movements of 44 glaucoma patients and 32 age-similar controls, while they watched a series of short video clips taken from television programs (Crabb et al., 2018) [6]. Gaze was recorded at 1000 Hz using a remote eye-tracker. We also provide demographic information and results from a clinical examination of vision for each participant.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Eye movements of glaucoma patients have been shown to differ from age-similar control groups when performing everyday tasks, such as reading (Burton et al., 2012; Smith et al., 2014) [1,2], visual search (Smith et al., 2012) [3], face recognition (Glen et al., 2013) [4], driving, and viewing static images (Smith et al., 2012) [5]. Described here is the dataset from a recent publication in which we compared the eye movements of 44 glaucoma patients and 32 age-similar controls, while they watched a series of short video clips taken from television programs (Crabb et al., 2018) [6]. Gaze was recorded at 1000 Hz using a remote eye-tracker. We also provide demographic information and results from a clinical examination of vision for each participant. |
Daniel S Asfaw; Pete R Jones; M M Vera; Nicholas D Smith; David P Crabb Does glaucoma alter eye movements when viewing images of natural scenes ? A between-eye study Journal Article Investigative Ophthalmology & Visual Science, 59 (8), pp. 3189–3198, 2018. @article{Asfaw2018a, title = {Does glaucoma alter eye movements when viewing images of natural scenes ? A between-eye study}, author = {Daniel S Asfaw and Pete R Jones and M M Vera and Nicholas D Smith and David P Crabb}, doi = {10.1167/iovs.18-23779}, year = {2018}, date = {2018-01-01}, journal = {Investigative Ophthalmology & Visual Science}, volume = {59}, number = {8}, pages = {3189--3198}, abstract = {PURPOSE. To investigate whether glaucoma produces measurable changes in eye movements. METHODS. Fifteen glaucoma patients with asymmetric vision loss (difference in mean deviation [MD] textgreater 6 dB between eyes) were asked to monocularly view 120 images of natural scenes, presented sequentially on a computer monitor. Each image was viewed twice—once each with the better and worse eye. Patients' eye movements were recorded with an Eyelink 1000 eye-tracker. Eye-movement parameters were computed and compared within participants (better eye versus worse eye). These parameters included a novel measure: saccadic reversal rate (SRR), as well as more traditional metrics such as saccade amplitude, fixation counts, fixation duration, and spread of fixation locations (bivariate contour ellipse area [BCEA]). In addition, the associations of these parameters with clinical measures of vision were investigated. RESULTS. In the worse eye, saccade amplitude (p = 0.012; -13%) and BCEA (p = 0.005; -16 %) were smaller, while SRR was greater (p = 0.018; +16%). There was a significant correlation between the intereye difference in BCEA, and differences in MD values (Spearman's r = 0.65; p = 0.01), while differences in SRR were associated with differences in visual acuity (Spearman's r = 0.64; p = 0.01). Furthermore, between-eye differences in BCEA were a significant predictor of between-eye differences in MD: for every 1-dB difference in MD, BCEA reduced by 6.2% (95% confidence interval, 1.6%–10.3%). CONCLUSIONS. Eye movements are altered by visual field loss, and these changes are related to changes in clinical measures. Eye movements recorded while passively viewing images could potentially be used as biomarkers for visual field damage.}, keywords = {}, pubstate = {published}, tppubtype = {article} } PURPOSE. To investigate whether glaucoma produces measurable changes in eye movements. METHODS. Fifteen glaucoma patients with asymmetric vision loss (difference in mean deviation [MD] textgreater 6 dB between eyes) were asked to monocularly view 120 images of natural scenes, presented sequentially on a computer monitor. Each image was viewed twice—once each with the better and worse eye. Patients' eye movements were recorded with an Eyelink 1000 eye-tracker. Eye-movement parameters were computed and compared within participants (better eye versus worse eye). These parameters included a novel measure: saccadic reversal rate (SRR), as well as more traditional metrics such as saccade amplitude, fixation counts, fixation duration, and spread of fixation locations (bivariate contour ellipse area [BCEA]). In addition, the associations of these parameters with clinical measures of vision were investigated. RESULTS. In the worse eye, saccade amplitude (p = 0.012; -13%) and BCEA (p = 0.005; -16 %) were smaller, while SRR was greater (p = 0.018; +16%). There was a significant correlation between the intereye difference in BCEA, and differences in MD values (Spearman's r = 0.65; p = 0.01), while differences in SRR were associated with differences in visual acuity (Spearman's r = 0.64; p = 0.01). Furthermore, between-eye differences in BCEA were a significant predictor of between-eye differences in MD: for every 1-dB difference in MD, BCEA reduced by 6.2% (95% confidence interval, 1.6%–10.3%). CONCLUSIONS. Eye movements are altered by visual field loss, and these changes are related to changes in clinical measures. Eye movements recorded while passively viewing images could potentially be used as biomarkers for visual field damage. |
Mania Asgharpour; Mehdi Tehrani-Doost; Mehrnoosh Ahmadi; Hamid Moshki Visual attention to emotional face in schizophrenia: An eye tracking study Journal Article Iranian Journal of Psychiatry, 10 (1), pp. 13–18, 2015. @article{Asgharpour2015, title = {Visual attention to emotional face in schizophrenia: An eye tracking study}, author = {Mania Asgharpour and Mehdi Tehrani-Doost and Mehrnoosh Ahmadi and Hamid Moshki}, doi = {10.1186/1471-2180-9-74r1471-2180-9-74 [pii]}, year = {2015}, date = {2015-01-01}, journal = {Iranian Journal of Psychiatry}, volume = {10}, number = {1}, pages = {13--18}, abstract = {OBJECTIVE: Deficits in the processing of facial emotions have been reported extensively in patients with schizophrenia. To explore whether restricted attention is the cause of impaired emotion processing in these patients, we examined visual attention through tracking eye movements in response to emotional and neutral face stimuli in a group of patients with schizophrenia and healthy individuals. We also examined the correlation between visual attention allocation and symptoms severity in our patient group. METHOD: Thirty adult patients with schizophrenia and 30 matched healthy controls participated in this study. Visual attention data were recorded while participants passively viewed emotional-neutral face pairs for 500 ms. The relationship between the visual attention and symptoms severity were assessed by the Positive and Negative Syndrome Scale (PANSS) in the schizophrenia group. Repeated Measures ANOVAs were used to compare the groups. RESULTS: Comparing the number of fixations made during face-pairs presentation, we found that patients with schizophrenia made fewer fixations on faces, regardless of the expression of the face. Analysis of the number of fixations on negative-neutral pairs also revealed that the patients made fewer fixations on both neutral and negative faces. Analysis of number of fixations on positive-neutral pairs only showed more fixations on positive relative to neutral expressions in both groups. We found no correlations between visual attention pattern to faces and symptom severity in schizophrenic patients. CONCLUSION: The results of this study suggest that the facial recognition deficit in schizophrenia is related to decreased attention to face stimuli. Finding of no difference in visual attention for positive-neutral face pairs between the groups is in line with studies that have shown increased ability to positive emotional perception in these patients.}, keywords = {}, pubstate = {published}, tppubtype = {article} } OBJECTIVE: Deficits in the processing of facial emotions have been reported extensively in patients with schizophrenia. To explore whether restricted attention is the cause of impaired emotion processing in these patients, we examined visual attention through tracking eye movements in response to emotional and neutral face stimuli in a group of patients with schizophrenia and healthy individuals. We also examined the correlation between visual attention allocation and symptoms severity in our patient group. METHOD: Thirty adult patients with schizophrenia and 30 matched healthy controls participated in this study. Visual attention data were recorded while participants passively viewed emotional-neutral face pairs for 500 ms. The relationship between the visual attention and symptoms severity were assessed by the Positive and Negative Syndrome Scale (PANSS) in the schizophrenia group. Repeated Measures ANOVAs were used to compare the groups. RESULTS: Comparing the number of fixations made during face-pairs presentation, we found that patients with schizophrenia made fewer fixations on faces, regardless of the expression of the face. Analysis of the number of fixations on negative-neutral pairs also revealed that the patients made fewer fixations on both neutral and negative faces. Analysis of number of fixations on positive-neutral pairs only showed more fixations on positive relative to neutral expressions in both groups. We found no correlations between visual attention pattern to faces and symptom severity in schizophrenic patients. CONCLUSION: The results of this study suggest that the facial recognition deficit in schizophrenia is related to decreased attention to face stimuli. Finding of no difference in visual attention for positive-neutral face pairs between the groups is in line with studies that have shown increased ability to positive emotional perception in these patients. |
Serguei V Astafiev; Gordon L Shulman; Nicholas V Metcalf; Jennifer Rengachary; Christine L MacDonald; Deborah L Harrington; Jun Maruta; Joshua S Shimony; Jamshid Ghajar; Mithun Diwakar; Ming-Xiong X Huang; Roland R Lee; Maurizio Corbetta Abnormal white matter blood-oxygen-level–dependent signals in chronic mild traumatic brain injury Journal Article Journal of Neurotrauma, 32 (16), pp. 1254–1271, 2015. @article{Astafiev2015, title = {Abnormal white matter blood-oxygen-level–dependent signals in chronic mild traumatic brain injury}, author = {Serguei V Astafiev and Gordon L Shulman and Nicholas V Metcalf and Jennifer Rengachary and Christine L MacDonald and Deborah L Harrington and Jun Maruta and Joshua S Shimony and Jamshid Ghajar and Mithun Diwakar and Ming-Xiong X Huang and Roland R Lee and Maurizio Corbetta}, doi = {10.1089/neu.2014.3547}, year = {2015}, date = {2015-01-01}, journal = {Journal of Neurotrauma}, volume = {32}, number = {16}, pages = {1254--1271}, abstract = {Concussion, or mild traumatic brain injury (mTBI), can cause persistent behavioral symptoms and cognitive impairment, but it is unclear if this condition is associated with detectable structural or functional brain changes. At two sites, chronic mTBI human subjects with persistent post-concussive symptoms (three months to five years after injury) and age- and education-matched healthy human control subjects underwent extensive neuropsychological and visual tracking eye movement tests. At one site, patients and controls also performed the visual tracking tasks while blood-oxygen-level-dependent (BOLD) signals were measured with functional magnetic resonance imaging. Although neither neuropsychological nor visual tracking measures distinguished patients from controls at the level of individual subjects, abnormal BOLD signals were reliably detected in patients. The most consistent changes were localized in white matter regions: anterior internal capsule and superior longitudinal fasciculus. In contrast, BOLD signals were normal in cortical regions, such as the frontal eye field and intraparietal sulcus, that mediate oculomotor and attention functions necessary for visual tracking. The abnormal BOLD signals accurately differentiated chronic mTBI patients from healthy controls at the single-subject level, although they did not correlate with symptoms or neuropsychological performance. We conclude that subjects with persistent post-concussive symptoms can be identified years after their TBI using fMRI and an eye movement task despite showing normal structural MRI and DTI.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Concussion, or mild traumatic brain injury (mTBI), can cause persistent behavioral symptoms and cognitive impairment, but it is unclear if this condition is associated with detectable structural or functional brain changes. At two sites, chronic mTBI human subjects with persistent post-concussive symptoms (three months to five years after injury) and age- and education-matched healthy human control subjects underwent extensive neuropsychological and visual tracking eye movement tests. At one site, patients and controls also performed the visual tracking tasks while blood-oxygen-level-dependent (BOLD) signals were measured with functional magnetic resonance imaging. Although neither neuropsychological nor visual tracking measures distinguished patients from controls at the level of individual subjects, abnormal BOLD signals were reliably detected in patients. The most consistent changes were localized in white matter regions: anterior internal capsule and superior longitudinal fasciculus. In contrast, BOLD signals were normal in cortical regions, such as the frontal eye field and intraparietal sulcus, that mediate oculomotor and attention functions necessary for visual tracking. The abnormal BOLD signals accurately differentiated chronic mTBI patients from healthy controls at the single-subject level, although they did not correlate with symptoms or neuropsychological performance. We conclude that subjects with persistent post-concussive symptoms can be identified years after their TBI using fMRI and an eye movement task despite showing normal structural MRI and DTI. |
Serguei V Astafiev; Kristina L Zinn; Gordon L Shulman; Maurizio Corbetta Exploring the physiological correlates of chronic mild traumatic brain injury symptoms Journal Article NeuroImage: Clinical, 11 , pp. 10–19, 2016. @article{Astafiev2016, title = {Exploring the physiological correlates of chronic mild traumatic brain injury symptoms}, author = {Serguei V Astafiev and Kristina L Zinn and Gordon L Shulman and Maurizio Corbetta}, doi = {10.1016/j.nicl.2016.01.004}, year = {2016}, date = {2016-01-01}, journal = {NeuroImage: Clinical}, volume = {11}, pages = {10--19}, publisher = {Elsevier}, abstract = {We report on the results of a multimodal imaging study involving behavioral assessments, evoked and resting-state BOLD fMRI, and DTI in chronic mTBI subjects. We found that larger task-evoked BOLD activity in the MT+/LO region in extra-striate visual cortex correlated with mTBI and PTSD symptoms, especially light sensitivity. Moreover, higher FA values near the left optic radiation (OR) were associated with both light sensitivity and higher BOLD activity in the MT+/LO region. The MT+/LO region was localized as a region of abnormal functional connectivity with central white matter regions previously found to have abnormal physiological signals during visual eye movement tracking (Astafiev et al., 2015). We conclude that mTBI symptoms and light sensitivity may be related to excessive responsiveness of visual cortex to sensory stimuli. This abnormal sensitivity may be related to chronic remodeling of white matter visual pathways acutely injured.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We report on the results of a multimodal imaging study involving behavioral assessments, evoked and resting-state BOLD fMRI, and DTI in chronic mTBI subjects. We found that larger task-evoked BOLD activity in the MT+/LO region in extra-striate visual cortex correlated with mTBI and PTSD symptoms, especially light sensitivity. Moreover, higher FA values near the left optic radiation (OR) were associated with both light sensitivity and higher BOLD activity in the MT+/LO region. The MT+/LO region was localized as a region of abnormal functional connectivity with central white matter regions previously found to have abnormal physiological signals during visual eye movement tracking (Astafiev et al., 2015). We conclude that mTBI symptoms and light sensitivity may be related to excessive responsiveness of visual cortex to sensory stimuli. This abnormal sensitivity may be related to chronic remodeling of white matter visual pathways acutely injured. |
Jeroen Atsma; Femke Maij; Brian D Corneil; Pieter W Medendorp No perisaccadic mislocalization with abruptly cancelled saccades Journal Article Journal of Neuroscience, 34 (16), pp. 5497–5504, 2014. @article{Atsma2014, title = {No perisaccadic mislocalization with abruptly cancelled saccades}, author = {Jeroen Atsma and Femke Maij and Brian D Corneil and Pieter W Medendorp}, doi = {10.1523/JNEUROSCI.4773-13.2014}, year = {2014}, date = {2014-01-01}, journal = {Journal of Neuroscience}, volume = {34}, number = {16}, pages = {5497--5504}, abstract = {Every saccadic eye movement that we make changes the image of the world on our retina. Yet, despite these retinal shifts, we still perceive our visual world to be stable. Efference copy from the oculomotor system to the visual system has been suggested to contribute to this stable percept, enabling the brain to anticipate the retinal image shifts by remapping the neural image. A psychophysical phenomenon that has been linked to this predictive remapping is the mislocalization of a stimulus flashed around the time of a saccade. If this mislocalization is initiated by saccade preparation, one should also observe localization errors when a saccade is planned, but abruptly aborted just before its execution. We tested this hypothesis in human subjects using a novel paradigm that combines a flash localization task with a countermanding component that occasionally requires saccade cancellation. Surprisingly, we found no trace of mislocalization, even for saccades cancelled close to the point of no return. This strongly suggests that the actual execution of the saccade is a prerequisite for the typical localization errors, which rejects various models and constrains neural substrates. We conclude that perisaccadic mislocalization is not a direct consequence of saccade preparation, but arises after saccade execution when the flash location is constructed from memory.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Every saccadic eye movement that we make changes the image of the world on our retina. Yet, despite these retinal shifts, we still perceive our visual world to be stable. Efference copy from the oculomotor system to the visual system has been suggested to contribute to this stable percept, enabling the brain to anticipate the retinal image shifts by remapping the neural image. A psychophysical phenomenon that has been linked to this predictive remapping is the mislocalization of a stimulus flashed around the time of a saccade. If this mislocalization is initiated by saccade preparation, one should also observe localization errors when a saccade is planned, but abruptly aborted just before its execution. We tested this hypothesis in human subjects using a novel paradigm that combines a flash localization task with a countermanding component that occasionally requires saccade cancellation. Surprisingly, we found no trace of mislocalization, even for saccades cancelled close to the point of no return. This strongly suggests that the actual execution of the saccade is a prerequisite for the typical localization errors, which rejects various models and constrains neural substrates. We conclude that perisaccadic mislocalization is not a direct consequence of saccade preparation, but arises after saccade execution when the flash location is constructed from memory. |
Jeroen Atsma; Femke Maij; Mathieu Koppen; David E Irwin; Pieter W Medendorp Causal inference for spatial constancy across saccades Journal Article PLoS Computational Biology, 12 (3), pp. 1–20, 2016. @article{Atsma2016, title = {Causal inference for spatial constancy across saccades}, author = {Jeroen Atsma and Femke Maij and Mathieu Koppen and David E Irwin and Pieter W Medendorp}, doi = {10.1371/journal.pcbi.1004766}, year = {2016}, date = {2016-01-01}, journal = {PLoS Computational Biology}, volume = {12}, number = {3}, pages = {1--20}, abstract = {Our ability to interact with the environment hinges on creating a stable visual world despite the continuous changes in retinal input. To achieve visual stability, the brain must distinguish the retinal image shifts caused by eye movements and shifts due to movements of the visual scene. This process appears not to be flawless: during saccades, we often fail to detect whether visual objects remain stable or move, which is called saccadic suppression of displacement (SSD). How does the brain evaluate the memorized information of the presaccadic scene and the actual visual feedback of the postsaccadic visual scene in the computations for visual stability? Using a SSD task, we test how participants localize the presaccadic position of the fixation target, the saccade target or a peripheral non-foveated target that was displaced parallel or orthogonal during a horizontal saccade, and subsequently viewed for three different durations. Results showed different localization errors of the three targets, depending on the viewing time of the postsaccadic stimulus and its spatial separation from the presaccadic location. We modeled the data through a Bayesian causal inference mechanism, in which at the trial level an optimal mixing of two possible strategies, integration vs. separation of the presaccadic memory and the postsaccadic sensory signals, is applied. Fits of this model generally outperformed other plausible decision strategies for producing SSD. Our findings suggest that humans exploit a Bayesian inference process with two causal structures to mediate visual stability.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Our ability to interact with the environment hinges on creating a stable visual world despite the continuous changes in retinal input. To achieve visual stability, the brain must distinguish the retinal image shifts caused by eye movements and shifts due to movements of the visual scene. This process appears not to be flawless: during saccades, we often fail to detect whether visual objects remain stable or move, which is called saccadic suppression of displacement (SSD). How does the brain evaluate the memorized information of the presaccadic scene and the actual visual feedback of the postsaccadic visual scene in the computations for visual stability? Using a SSD task, we test how participants localize the presaccadic position of the fixation target, the saccade target or a peripheral non-foveated target that was displaced parallel or orthogonal during a horizontal saccade, and subsequently viewed for three different durations. Results showed different localization errors of the three targets, depending on the viewing time of the postsaccadic stimulus and its spatial separation from the presaccadic location. We modeled the data through a Bayesian causal inference mechanism, in which at the trial level an optimal mixing of two possible strategies, integration vs. separation of the presaccadic memory and the postsaccadic sensory signals, is applied. Fits of this model generally outperformed other plausible decision strategies for producing SSD. Our findings suggest that humans exploit a Bayesian inference process with two causal structures to mediate visual stability. |
Sheena K Au-Yeung; Valerie Benson; Monica S Castelhano; Keith Rayner Eye movement sequences during simple versus complex information processing of scenes in autism spectrum disorder Journal Article Autism Research and Treatment, 2011 , pp. 1–7, 2011. @article{Au-Yeung2011, title = {Eye movement sequences during simple versus complex information processing of scenes in autism spectrum disorder}, author = {Sheena K Au-Yeung and Valerie Benson and Monica S Castelhano and Keith Rayner}, doi = {10.1155/2011/657383}, year = {2011}, date = {2011-01-01}, journal = {Autism Research and Treatment}, volume = {2011}, pages = {1--7}, abstract = {Minshew and Goldstein (1998) postulated that autism spectrum disorder (ASD) is a disorder of complex information processing. The current study was designed to investigate this hypothesis. Participants with and without ASD completed two scene perception tasks: a simple “spot the difference” task, where they had to say which one of a pair of pictures had a detail missing, and a complex “which one's weird” task, where they had to decide which one of a pair of pictures looks “weird”. Participants with ASD did not differ from TD participants in their ability to accurately identify the target picture in both tasks. However, analysis of the eye movement sequences showed that participants with ASD viewed scenes differently from normal controls exclusively for the complex task. This difference in eye movement patterns, and the method used to examine different patterns, adds to the knowledge base regarding eye movements and ASD. Our results are in accordance with Minshew and Goldstein's theory that complex, but not simple, information processing is impaired in ASD.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Minshew and Goldstein (1998) postulated that autism spectrum disorder (ASD) is a disorder of complex information processing. The current study was designed to investigate this hypothesis. Participants with and without ASD completed two scene perception tasks: a simple “spot the difference” task, where they had to say which one of a pair of pictures had a detail missing, and a complex “which one's weird” task, where they had to decide which one of a pair of pictures looks “weird”. Participants with ASD did not differ from TD participants in their ability to accurately identify the target picture in both tasks. However, analysis of the eye movement sequences showed that participants with ASD viewed scenes differently from normal controls exclusively for the complex task. This difference in eye movement patterns, and the method used to examine different patterns, adds to the knowledge base regarding eye movements and ASD. Our results are in accordance with Minshew and Goldstein's theory that complex, but not simple, information processing is impaired in ASD. |
Sheena K Au-Yeung; Johanna K Kaakinen; Valerie Benson Cognitive perspective-taking during scene perception in autism spectrum disorder: Evidence from eye movements Journal Article Autism Research, 7 (1), pp. 84–93, 2014. @article{Au-Yeung2014, title = {Cognitive perspective-taking during scene perception in autism spectrum disorder: Evidence from eye movements}, author = {Sheena K Au-Yeung and Johanna K Kaakinen and Valerie Benson}, doi = {10.1002/aur.1352}, year = {2014}, date = {2014-01-01}, journal = {Autism Research}, volume = {7}, number = {1}, pages = {84--93}, abstract = {The present study examined how eye movements during scene viewing are modulated by adopting psychological perspectives in both adults with autism spectrum disorders (ASD) and typically developing adults. In the current study, participants viewed house scenes with either non-perspective-taking (look for valuable items/features of the house that need fixing) or perspective-taking instructions (imagine that you are a burglar/repairman) while their eye movements were recorded. The eye movement measures revealed that for the “look for the valuable items” and burglar perspective task, the ASD group showed typical relevance effects (the preference to look at schema-relevant compared with schema-irrelevant targets) in their eye movements. However, we found subtle processing differences between the groups that were related to initial orienting to and processing of schema-relevant items for the “look for the features that need fixing” and the repairman perspective-taking task. There was an absence of a relevance effect for the ASD group for the repairman perspective and its non-perspective-taking equivalent instruction showing that the identification of items relevant to those schemas was more difficult for the ASD group. The present findings suggest that resolving ambiguity may be a defining feature of complex information processing deficits in ASD}, keywords = {}, pubstate = {published}, tppubtype = {article} } The present study examined how eye movements during scene viewing are modulated by adopting psychological perspectives in both adults with autism spectrum disorders (ASD) and typically developing adults. In the current study, participants viewed house scenes with either non-perspective-taking (look for valuable items/features of the house that need fixing) or perspective-taking instructions (imagine that you are a burglar/repairman) while their eye movements were recorded. The eye movement measures revealed that for the “look for the valuable items” and burglar perspective task, the ASD group showed typical relevance effects (the preference to look at schema-relevant compared with schema-irrelevant targets) in their eye movements. However, we found subtle processing differences between the groups that were related to initial orienting to and processing of schema-relevant items for the “look for the features that need fixing” and the repairman perspective-taking task. There was an absence of a relevance effect for the ASD group for the repairman perspective and its non-perspective-taking equivalent instruction showing that the identification of items relevant to those schemas was more difficult for the ASD group. The present findings suggest that resolving ambiguity may be a defining feature of complex information processing deficits in ASD |
Sheena K Au-Yeung; Johanna K Kaakinen; Simon P Liversedge; Valerie Benson Processing of written irony in autism spectrum disorder: An eye-movement study Journal Article Autism Research, 8 (6), pp. 749–760, 2015. @article{Au-Yeung2015, title = {Processing of written irony in autism spectrum disorder: An eye-movement study}, author = {Sheena K Au-Yeung and Johanna K Kaakinen and Simon P Liversedge and Valerie Benson}, doi = {10.1002/aur.1490}, year = {2015}, date = {2015-01-01}, journal = {Autism Research}, volume = {8}, number = {6}, pages = {749--760}, abstract = {Previous research has suggested that individuals with Autism Spectrum Disorders (ASD) have difficulties understanding others communicative intent and with using contextual information to correctly interpret irony. We recorded the eye movements of typically developing (TD) adults ASD adults when they read statements that could either be interpreted as ironic or non-ironic depending on the context of the passage. Participants with ASD performed as well as TD controls in their comprehension accuracy for speaker's statements in both ironic and non-ironic conditions. Eye movement data showed that for both participant groups, total reading times were longer for the critical region containing the speaker's statement and a subsequent sentence restating the context in the ironic condition compared to the non-ironic condition. The results suggest that more effortful processing is required in both ASD and TD participants for ironic compared with literal non-ironic statements, and that individuals with ASD were able to use contextual information to infer a non-literal interpretation of ironic text. Individuals with ASD, however, spent more time overall than TD controls rereading the passages, to a similar degree across both ironic and non-ironic conditions, suggesting that they either take longer to construct a coherent discourse representation of the text, or that they take longer to make the decision that their representation of the text is reasonable based on their knowledge of the world.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Previous research has suggested that individuals with Autism Spectrum Disorders (ASD) have difficulties understanding others communicative intent and with using contextual information to correctly interpret irony. We recorded the eye movements of typically developing (TD) adults ASD adults when they read statements that could either be interpreted as ironic or non-ironic depending on the context of the passage. Participants with ASD performed as well as TD controls in their comprehension accuracy for speaker's statements in both ironic and non-ironic conditions. Eye movement data showed that for both participant groups, total reading times were longer for the critical region containing the speaker's statement and a subsequent sentence restating the context in the ironic condition compared to the non-ironic condition. The results suggest that more effortful processing is required in both ASD and TD participants for ironic compared with literal non-ironic statements, and that individuals with ASD were able to use contextual information to infer a non-literal interpretation of ironic text. Individuals with ASD, however, spent more time overall than TD controls rereading the passages, to a similar degree across both ironic and non-ironic conditions, suggesting that they either take longer to construct a coherent discourse representation of the text, or that they take longer to make the decision that their representation of the text is reasonable based on their knowledge of the world. |
Colas N Authié; Daniel R Mestre Optokinetic nystagmus is elicited by curvilinear optic flow during high speed curve driving Journal Article Vision Research, 51 (16), pp. 1791–1800, 2011. @article{Authie2011, title = {Optokinetic nystagmus is elicited by curvilinear optic flow during high speed curve driving}, author = {Colas N Authié and Daniel R Mestre}, doi = {10.1016/j.visres.2011.06.010}, year = {2011}, date = {2011-01-01}, journal = {Vision Research}, volume = {51}, number = {16}, pages = {1791--1800}, abstract = {When analyzing gaze behavior during curve driving, it is commonly accepted that gaze is mostly located in the vicinity of the tangent point, being the point where gaze direction tangents the curve inside edge. This approach neglects the fact that the tangent point is actually motionless only in the limit case when the trajectory precisely follows the curve's geometry. In this study, we measured gaze behavior during curve driving, with the general hypothesis that gaze is not static, when exposed to a global optical flow due to self-motion. In order to study spatio-temporal aspects of gaze during curve driving, we used a driving simulator coupled to a gaze recording system. Ten participants drove seven runs on a track composed of eight curves of various radii (50, 100, 200 and 500. m), with each radius appearing in both right and left directions. Results showed that average gaze position was, as previously described, located in the vicinity of the tangent point. However, analysis also revealed the presence of a systematic optokinetic nystagmus (OKN) around the tangent point position. The OKN slow phase direction does not match the local optic flow direction, while slow phase speed is about half of the local speed. Higher directional gains are observed when averaging the entire optical flow projected on the simulation display, whereas the best speed gain is obtained for a 2° optic flow area, centered on the instantaneous gaze location. The present study confirms that the tangent point is a privileged feature in the dynamic visual scene during curve driving, and underlines a contribution of the global optical flow to gaze behavior during active self-motion.}, keywords = {}, pubstate = {published}, tppubtype = {article} } When analyzing gaze behavior during curve driving, it is commonly accepted that gaze is mostly located in the vicinity of the tangent point, being the point where gaze direction tangents the curve inside edge. This approach neglects the fact that the tangent point is actually motionless only in the limit case when the trajectory precisely follows the curve's geometry. In this study, we measured gaze behavior during curve driving, with the general hypothesis that gaze is not static, when exposed to a global optical flow due to self-motion. In order to study spatio-temporal aspects of gaze during curve driving, we used a driving simulator coupled to a gaze recording system. Ten participants drove seven runs on a track composed of eight curves of various radii (50, 100, 200 and 500. m), with each radius appearing in both right and left directions. Results showed that average gaze position was, as previously described, located in the vicinity of the tangent point. However, analysis also revealed the presence of a systematic optokinetic nystagmus (OKN) around the tangent point position. The OKN slow phase direction does not match the local optic flow direction, while slow phase speed is about half of the local speed. Higher directional gains are observed when averaging the entire optical flow projected on the simulation display, whereas the best speed gain is obtained for a 2° optic flow area, centered on the instantaneous gaze location. The present study confirms that the tangent point is a privileged feature in the dynamic visual scene during curve driving, and underlines a contribution of the global optical flow to gaze behavior during active self-motion. |
Eric Avila; Jos N Van Der Geest; Sandra Kengne Kamga; Claire M Verhage; Opher Donchin; Maarten A Frens Cerebellar transcranial direct current stimulation effects on saccade adaptation Journal Article Neural Plasticity, 2015 , pp. 1–9, 2015. @article{Avila2015, title = {Cerebellar transcranial direct current stimulation effects on saccade adaptation}, author = {Eric Avila and Jos N {Van Der Geest} and Sandra {Kengne Kamga} and Claire M Verhage and Opher Donchin and Maarten A Frens}, doi = {10.1155/2015/968970}, year = {2015}, date = {2015-01-01}, journal = {Neural Plasticity}, volume = {2015}, pages = {1--9}, abstract = {Saccade adaptation is a cerebellar-mediated type of motor learning in which the oculomotor system is exposed to repetitive errors. Different types of saccade adaptations are thought to involve distinct underlying cerebellar mechanisms. Transcranial direct current stimulation (tDCS) induces changes in neuronal excitability in a polarity-specific manner and offers a modulatory, noninvasive, functional insight into the learning aspects of different brain regions. We aimed to modulate the cerebellar influence on saccade gains during adaptation using tDCS. Subjects performed an inward (n = 10) or outward (n = 10) saccade adaptation experiment (25% intrasaccadic target step) while receiving 1.5 mA of anodal cerebellar tDCS delivered by a small contact electrode. Compared to sham stimulation, tDCS increased learning of saccadic inward adaptation but did not affect learning of outward adaptation. This may imply that plasticity mechanisms in the cerebellum are different between inward and outward adaptation. TDCS could have influenced specific cerebellar areas that contribute to inward but not outward adaptation. We conclude that tDCS can be used as a neuromodulatory technique to alter cerebellar oculomotor output, arguably by engaging wider cerebellar areas and increasing the available resources for learning.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Saccade adaptation is a cerebellar-mediated type of motor learning in which the oculomotor system is exposed to repetitive errors. Different types of saccade adaptations are thought to involve distinct underlying cerebellar mechanisms. Transcranial direct current stimulation (tDCS) induces changes in neuronal excitability in a polarity-specific manner and offers a modulatory, noninvasive, functional insight into the learning aspects of different brain regions. We aimed to modulate the cerebellar influence on saccade gains during adaptation using tDCS. Subjects performed an inward (n = 10) or outward (n = 10) saccade adaptation experiment (25% intrasaccadic target step) while receiving 1.5 mA of anodal cerebellar tDCS delivered by a small contact electrode. Compared to sham stimulation, tDCS increased learning of saccadic inward adaptation but did not affect learning of outward adaptation. This may imply that plasticity mechanisms in the cerebellum are different between inward and outward adaptation. TDCS could have influenced specific cerebellar areas that contribute to inward but not outward adaptation. We conclude that tDCS can be used as a neuromodulatory technique to alter cerebellar oculomotor output, arguably by engaging wider cerebellar areas and increasing the available resources for learning. |
Reza Azadi; Mark R Harwood Visual cues that are effective for contextual saccade adaptation Journal Article Journal of Neurophysiology, 111 (11), pp. 2307–2319, 2014. @article{Azadi2014, title = {Visual cues that are effective for contextual saccade adaptation}, author = {Reza Azadi and Mark R Harwood}, doi = {10.1152/jn.00894.2013}, year = {2014}, date = {2014-01-01}, journal = {Journal of Neurophysiology}, volume = {111}, number = {11}, pages = {2307--2319}, abstract = {The accuracy of saccades, as maintained by saccade adaptation, has been shown to be context dependent: able to have different amplitude movements to the same retinal displacement dependent on motor contexts such as orbital starting location. There is conflicting evidence as to whether purely visual cues also effect contextual saccade adaptation and, if so, what function this might serve. We tested what visual cues might evoke contextual adaptation. Over 5 experiments, 78 naive subjects made saccades to circularly moving targets, which stepped outward or inward during the saccade depending on target movement direction, speed, or color and shape. To test if the movement or context postsaccade were critical, we stopped the postsaccade target motion ( experiment 4 ) or neutralized the contexts by equating postsaccade target speed to an intermediate value ( experiment 5 ). We found contextual adaptation in all conditions except those defined by color and shape. We conclude that some, but not all, visual cues before the saccade are sufficient for contextual adaptation. We conjecture that this visual contextuality functions to allow for different motor states for different coordinated movement patterns, such as coordinated saccade and pursuit motor planning.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The accuracy of saccades, as maintained by saccade adaptation, has been shown to be context dependent: able to have different amplitude movements to the same retinal displacement dependent on motor contexts such as orbital starting location. There is conflicting evidence as to whether purely visual cues also effect contextual saccade adaptation and, if so, what function this might serve. We tested what visual cues might evoke contextual adaptation. Over 5 experiments, 78 naive subjects made saccades to circularly moving targets, which stepped outward or inward during the saccade depending on target movement direction, speed, or color and shape. To test if the movement or context postsaccade were critical, we stopped the postsaccade target motion ( experiment 4 ) or neutralized the contexts by equating postsaccade target speed to an intermediate value ( experiment 5 ). We found contextual adaptation in all conditions except those defined by color and shape. We conclude that some, but not all, visual cues before the saccade are sufficient for contextual adaptation. We conjecture that this visual contextuality functions to allow for different motor states for different coordinated movement patterns, such as coordinated saccade and pursuit motor planning. |
Bobby Azarian; Elizabeth G Esser; Matthew S Peterson Evidence from the eyes: Threatening postures hold attention Journal Article Psychonomic Bulletin & Review, 23 (3), pp. 764–770, 2016. @article{Azarian2016b, title = {Evidence from the eyes: Threatening postures hold attention}, author = {Bobby Azarian and Elizabeth G Esser and Matthew S Peterson}, doi = {10.3758/s13423-015-0942-0}, year = {2016}, date = {2016-01-01}, journal = {Psychonomic Bulletin & Review}, volume = {23}, number = {3}, pages = {764--770}, publisher = {Psychonomic Bulletin & Review}, abstract = {Efficient detection of threat provides obvious survival advantages and has resulted in a fast and accurate threatdetection system. Although beneficial under normal circumstances, this system may become hypersensitive and cause threat-processing abnormalities. Past research has shown that anxious individuals have difficulty disengaging attention from threatening faces, but it is unknown whether other forms of threatening social stimuli also influence attentional orienting. Much like faces, human body postures are salient social stimuli, because they are informative of one's emotional state and next likely action. Additionally, postures can convey such information in situations in which another's facial expression is not easily visible. Here we investigated whether there is a threat-specific effect for high-anxious individuals, by measuring the time that it takes the eyes to leave the attended stimulus, a task-irrelevant body posture. The results showed that relative to nonthreating postures, threat-related postures hold attention in anxious individuals, providing further evidence of an anxiety-related attentional bias for threatening information. This is the first study to demonstrate that attentional disengagement from threatening postures is affected by emotional valence in those reporting anxiety.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Efficient detection of threat provides obvious survival advantages and has resulted in a fast and accurate threatdetection system. Although beneficial under normal circumstances, this system may become hypersensitive and cause threat-processing abnormalities. Past research has shown that anxious individuals have difficulty disengaging attention from threatening faces, but it is unknown whether other forms of threatening social stimuli also influence attentional orienting. Much like faces, human body postures are salient social stimuli, because they are informative of one's emotional state and next likely action. Additionally, postures can convey such information in situations in which another's facial expression is not easily visible. Here we investigated whether there is a threat-specific effect for high-anxious individuals, by measuring the time that it takes the eyes to leave the attended stimulus, a task-irrelevant body posture. The results showed that relative to nonthreating postures, threat-related postures hold attention in anxious individuals, providing further evidence of an anxiety-related attentional bias for threatening information. This is the first study to demonstrate that attentional disengagement from threatening postures is affected by emotional valence in those reporting anxiety. |
Benjamin T Backus; Daniel Matza-Brown The contribution of vergence change to the measurement of relative disparity Journal Article Journal of Vision, 3 (11), pp. 727–750, 2003. @article{Backus2003, title = {The contribution of vergence change to the measurement of relative disparity}, author = {Benjamin T Backus and Daniel Matza-Brown}, doi = {10.1167/3.11.8}, year = {2003}, date = {2003-01-01}, journal = {Journal of Vision}, volume = {3}, number = {11}, pages = {727--750}, abstract = {The relative disparity between two objects in a scene can in principle be measured directly from the retinal images, without knowledge of eye position. But relative disparity increment thresholds are lowest when the relative disparity is small and the objects are not widely separated in the visual field: thus, some relative disparities are easier for the visual system to measure than others. We consider, after others, a second method by which the visual system could measure relative disparity, based on change in vergence ("delta vergence" or DV). The DV mechanism could be more reliable than the retinal mechanism when visual targets are widely separated in visual direction or depth. We used a cue-conflict paradigm to measure the extent to which perceived depth depends on DV. As target separation increased, so did reliance on DV. As intertarget disparity increased, reliance on DV increased for one observer but not for two others.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The relative disparity between two objects in a scene can in principle be measured directly from the retinal images, without knowledge of eye position. But relative disparity increment thresholds are lowest when the relative disparity is small and the objects are not widely separated in the visual field: thus, some relative disparities are easier for the visual system to measure than others. We consider, after others, a second method by which the visual system could measure relative disparity, based on change in vergence ("delta vergence" or DV). The DV mechanism could be more reliable than the retinal mechanism when visual targets are widely separated in visual direction or depth. We used a cue-conflict paradigm to measure the extent to which perceived depth depends on DV. As target separation increased, so did reliance on DV. As intertarget disparity increased, reliance on DV increased for one observer but not for two others. |
Stephen P Badham; Claire V Hutchinson Characterising eye movement dysfunction in myalgic encephalomyelitis/ chronic fatigue syndrome Journal Article Graefe's Archive for Clinical and Experimental Ophthalmology, 251 (12), pp. 2769–2776, 2013. @article{Badham2013, title = {Characterising eye movement dysfunction in myalgic encephalomyelitis/ chronic fatigue syndrome}, author = {Stephen P Badham and Claire V Hutchinson}, doi = {10.1007/s00417-013-2431-3}, year = {2013}, date = {2013-01-01}, journal = {Graefe's Archive for Clinical and Experimental Ophthalmology}, volume = {251}, number = {12}, pages = {2769--2776}, abstract = {BACKGROUND: People who suffer from myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) often report that their eye movements are sluggish and that they have difficulties tracking moving objects. However, descriptions of these visual problems are based solely on patients' self-reports of their subjective visual experiences, and there is a distinct lack of empirical evidence to objectively verify their claims. This paper presents the first experimental research to objectively examine eye movements in those suffering from ME/CFS. METHODS: Patients were assessed for ME/CFS symptoms and were compared to age, gender, and education matched controls for their ability to generate saccades and smooth pursuit eye movements. RESULTS: Patients and controls exhibited similar error rates and saccade latencies (response times) on prosaccade and antisaccade tasks. Patients showed relatively intact ability to accurately fixate the target (prosaccades), but were impaired when required to focus accurately in a specific position opposite the target (antisaccades). Patients were most markedly impaired when required to direct their gaze as closely as possible to a smoothly moving target (smooth pursuit). CONCLUSIONS: It is hypothesised that the effects of ME/CFS can be overcome briefly for completion of saccades, but that continuous pursuit activity (accurately tracking a moving object), even for a short time period, highlights dysfunctional eye movement behaviour in ME/CFS patients. Future smooth pursuit research may elucidate and improve diagnosis of ME/CFS.}, keywords = {}, pubstate = {published}, tppubtype = {article} } BACKGROUND: People who suffer from myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) often report that their eye movements are sluggish and that they have difficulties tracking moving objects. However, descriptions of these visual problems are based solely on patients' self-reports of their subjective visual experiences, and there is a distinct lack of empirical evidence to objectively verify their claims. This paper presents the first experimental research to objectively examine eye movements in those suffering from ME/CFS. METHODS: Patients were assessed for ME/CFS symptoms and were compared to age, gender, and education matched controls for their ability to generate saccades and smooth pursuit eye movements. RESULTS: Patients and controls exhibited similar error rates and saccade latencies (response times) on prosaccade and antisaccade tasks. Patients showed relatively intact ability to accurately fixate the target (prosaccades), but were impaired when required to focus accurately in a specific position opposite the target (antisaccades). Patients were most markedly impaired when required to direct their gaze as closely as possible to a smoothly moving target (smooth pursuit). CONCLUSIONS: It is hypothesised that the effects of ME/CFS can be overcome briefly for completion of saccades, but that continuous pursuit activity (accurately tracking a moving object), even for a short time period, highlights dysfunctional eye movement behaviour in ME/CFS patients. Future smooth pursuit research may elucidate and improve diagnosis of ME/CFS. |
Jeremy B Badler; Philippe Lefèvre; Marcus Missal Anticipatory pursuit is influenced by a concurrent timing task. Journal Article Journal of Vision, 8 (16), pp. 1–9, 2008. @article{Badler2008, title = {Anticipatory pursuit is influenced by a concurrent timing task.}, author = {Jeremy B Badler and Philippe Lef{è}vre and Marcus Missal}, doi = {10.1167/8.6.672}, year = {2008}, date = {2008-01-01}, journal = {Journal of Vision}, volume = {8}, number = {16}, pages = {1--9}, abstract = {The ability to predict upcoming events is important to compensate for relatively long sensory-motor delays. When stimuli are temporally regular, their prediction depends on a representation of elapsed time. However, it is well known that the allocation of attention to the timing of an upcoming event alters this representation. The role of attention on the temporal processing component of prediction was investigated in a visual smooth pursuit task that was performed either in isolation or concurrently with a manual response task. Subjects used smooth pursuit eye movements to accurately track a moving target after a constant-duration delay interval. In the manual response task, subjects had to estimate the instant of target motion onset by pressing a button. The onset of anticipatory pursuit eye movements was used to quantify the subject's estimate of elapsed time. We found that onset times were delayed significantly in the presence of the concurrent manual task relative to the pursuit task in isolation. There was also a correlation between the oculomotor and manual response latencies. In the framework of Scalar Timing Theory, the results are consistent with a centralized attentional gating mechanism that allocates clock resources between smooth pursuit preparation and the parallel timing task.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The ability to predict upcoming events is important to compensate for relatively long sensory-motor delays. When stimuli are temporally regular, their prediction depends on a representation of elapsed time. However, it is well known that the allocation of attention to the timing of an upcoming event alters this representation. The role of attention on the temporal processing component of prediction was investigated in a visual smooth pursuit task that was performed either in isolation or concurrently with a manual response task. Subjects used smooth pursuit eye movements to accurately track a moving target after a constant-duration delay interval. In the manual response task, subjects had to estimate the instant of target motion onset by pressing a button. The onset of anticipatory pursuit eye movements was used to quantify the subject's estimate of elapsed time. We found that onset times were delayed significantly in the presence of the concurrent manual task relative to the pursuit task in isolation. There was also a correlation between the oculomotor and manual response latencies. In the framework of Scalar Timing Theory, the results are consistent with a centralized attentional gating mechanism that allocates clock resources between smooth pursuit preparation and the parallel timing task. |
T Balsdon; R Schweitzer; T L Watson; M Rolfs All is not lost: Post-saccadic contributions to the perceptual omission of intra-saccadic streaks Journal Article Consciousness and Cognition, 64 , pp. 19–31, 2018. @article{Balsdon2018, title = {All is not lost: Post-saccadic contributions to the perceptual omission of intra-saccadic streaks}, author = {T Balsdon and R Schweitzer and T L Watson and M Rolfs}, doi = {10.1016/j.concog.2018.05.004}, year = {2018}, date = {2018-01-01}, journal = {Consciousness and Cognition}, volume = {64}, pages = {19--31}, publisher = {Elsevier}, abstract = {Saccades rapidly jerk the eye into new positions, yet we rarely experience the motion streaks imposed on the retinal image. Here we examined spatial and temporal properties of post-saccadic masking—one potential explanation of this perceptual omission. Observers judged the motion direction of a target stimulus, a Gaussian blob, that moved vertically upwards or downwards and then back to its initial position, just as observers made a saccade. We manipulated the onset and offset of the target and of distractors in various spatial relations to the target, and assessed their effect on performance and subjective confidence. Although the presence of the target after the saccade caused the strongest omission, the offset of spatially distant distractor stimuli upon saccade offset also impaired performance. The temporal properties of these two separate effects suggest that, in addition to masking, an independent effect of attentional distraction further accentuates perceptual omission of intra-saccadic motion streaks.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Saccades rapidly jerk the eye into new positions, yet we rarely experience the motion streaks imposed on the retinal image. Here we examined spatial and temporal properties of post-saccadic masking—one potential explanation of this perceptual omission. Observers judged the motion direction of a target stimulus, a Gaussian blob, that moved vertically upwards or downwards and then back to its initial position, just as observers made a saccade. We manipulated the onset and offset of the target and of distractors in various spatial relations to the target, and assessed their effect on performance and subjective confidence. Although the presence of the target after the saccade caused the strongest omission, the offset of spatially distant distractor stimuli upon saccade offset also impaired performance. The temporal properties of these two separate effects suggest that, in addition to masking, an independent effect of attentional distraction further accentuates perceptual omission of intra-saccadic motion streaks. |
Daniela Balslev; Bartholomaus Odoj; Hans-Otto Karnath Role of somatosensory cortex in visuospatial attention Journal Article Journal of Neuroscience, 33 (46), pp. 18311–18318, 2013. @article{Balslev2013, title = {Role of somatosensory cortex in visuospatial attention}, author = {Daniela Balslev and Bartholomaus Odoj and Hans-Otto Karnath}, doi = {10.1523/JNEUROSCI.1112-13.2013}, year = {2013}, date = {2013-01-01}, journal = {Journal of Neuroscience}, volume = {33}, number = {46}, pages = {18311--18318}, abstract = {The human somatosensory cortex (S1) is not among the brain areas usually associated with visuospatial attention. However, such a function can be presumed, given the recently identified eye proprioceptive input to S1 and the established links between gaze and attention. Here we investigated a rare patient with a focal lesion of the right postcentral gyrus that interferes with the processing of eye proprioception without affecting the ability to locate visual objects relative to her body or to execute eye movements. As a behavioral measure of spatial attention, we recorded fixation time during visual search and reaction time for visual discrimination in lateral displays. In contrast to a group of age-matched controls, the patient showed a gradient in looking time and in visual sensitivity toward the midline. Because an attention bias in the opposite direction, toward the ipsilesional space, occurs in patients with spatial neglect, in a second study, we asked whether the incidental coinjury of S1 together with the neglect-typical perisylvian lesion leads to a milder neglect. A voxelwise lesion behavior mapping analysis of a group of right-hemisphere stroke patients supported this hypothesis. The effect of an isolated S1 lesion on visual exploration and visual sensitivity as well as the modulatory role of S1 in spatial neglect suggest a role of this area in visuospatial attention. We hypothesize that the proprioceptive gaze signal in S1, although playing only a minor role in locating visual objects relative to the body, affects the allocation of attention in the visual space.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The human somatosensory cortex (S1) is not among the brain areas usually associated with visuospatial attention. However, such a function can be presumed, given the recently identified eye proprioceptive input to S1 and the established links between gaze and attention. Here we investigated a rare patient with a focal lesion of the right postcentral gyrus that interferes with the processing of eye proprioception without affecting the ability to locate visual objects relative to her body or to execute eye movements. As a behavioral measure of spatial attention, we recorded fixation time during visual search and reaction time for visual discrimination in lateral displays. In contrast to a group of age-matched controls, the patient showed a gradient in looking time and in visual sensitivity toward the midline. Because an attention bias in the opposite direction, toward the ipsilesional space, occurs in patients with spatial neglect, in a second study, we asked whether the incidental coinjury of S1 together with the neglect-typical perisylvian lesion leads to a milder neglect. A voxelwise lesion behavior mapping analysis of a group of right-hemisphere stroke patients supported this hypothesis. The effect of an isolated S1 lesion on visual exploration and visual sensitivity as well as the modulatory role of S1 in spatial neglect suggest a role of this area in visuospatial attention. We hypothesize that the proprioceptive gaze signal in S1, although playing only a minor role in locating visual objects relative to the body, affects the allocation of attention in the visual space. |
Chiara Banfi; Ferenc Kemény; Melanie Gangl; Gerd Schulte-Körne; Kristina Moll; Karin Landerl Visual attention span performance in German-speaking children with differential reading and spelling profiles: No evidence of group differences Journal Article Plos One, 13 (6), pp. 1–17, 2018. @article{Banfi2018, title = {Visual attention span performance in German-speaking children with differential reading and spelling profiles: No evidence of group differences}, author = {Chiara Banfi and Ferenc Kemény and Melanie Gangl and Gerd Schulte-Körne and Kristina Moll and Karin Landerl}, doi = {10.1371/journal.pone.0198903}, year = {2018}, date = {2018-01-01}, journal = {Plos One}, volume = {13}, number = {6}, pages = {1--17}, abstract = {An impairment in the visual attention span (VAS) has been suggested to hamper reading performance of individuals with dyslexia. It is not clear, however, if the very nature of the deficit is visual or verbal and, importantly, if it affects spelling skills as well. The current study investigated VAS by means of forced choice tasks with letters and symbols in a sample of third and fourth graders with age-adequate reading and spelling skills (n= 43), a typical dyslexia profile with combined reading and spelling deficits (n= 26) and isolated spelling deficits (n= 32). The task was devised to contain low phonological short-term memory load and to overcome the limitations of oral reports. Notably, eye-movements were monitored to control that children fixated the center of the display when stimuli were presented. Results yielded no main effect of group as well as no group-related interactions, thus showing that children with dyslexia and isolated spelling deficits did not manifest a VAS deficit for letters or symbols once certain methodological aspects were controlled for. The present results could not replicate previous evidence for the involvement of VAS in reading and dyslexia.}, keywords = {}, pubstate = {published}, tppubtype = {article} } An impairment in the visual attention span (VAS) has been suggested to hamper reading performance of individuals with dyslexia. It is not clear, however, if the very nature of the deficit is visual or verbal and, importantly, if it affects spelling skills as well. The current study investigated VAS by means of forced choice tasks with letters and symbols in a sample of third and fourth graders with age-adequate reading and spelling skills (n= 43), a typical dyslexia profile with combined reading and spelling deficits (n= 26) and isolated spelling deficits (n= 32). The task was devised to contain low phonological short-term memory load and to overcome the limitations of oral reports. Notably, eye-movements were monitored to control that children fixated the center of the display when stimuli were presented. Results yielded no main effect of group as well as no group-related interactions, thus showing that children with dyslexia and isolated spelling deficits did not manifest a VAS deficit for letters or symbols once certain methodological aspects were controlled for. The present results could not replicate previous evidence for the involvement of VAS in reading and dyslexia. |
Sonia Bansal; Laurence C Jayet Bray; Matthew S Peterson; Wilsaan M Joiner The effect of saccade metrics on the corollary discharge contribution to perceived eye location Journal Article Journal of Neurophysiology, 113 (9), pp. 3312–3322, 2015. @article{Bansal2015, title = {The effect of saccade metrics on the corollary discharge contribution to perceived eye location}, author = {Sonia Bansal and Laurence C {Jayet Bray} and Matthew S Peterson and Wilsaan M Joiner}, doi = {10.1152/jn.00771.2014}, year = {2015}, date = {2015-01-01}, journal = {Journal of Neurophysiology}, volume = {113}, number = {9}, pages = {3312--3322}, abstract = {The effect of saccade metrics on the corollary discharge contribution to per- ceived eye location. J Neurophysiol 113: 3312–3322, 2015. First published March 11, 2015; doi:10.1152/jn.00771.2014.—Corollary discharge (CD) is hypothesized to provide the movement information (direction and amplitude) required to compensate for the saccade- induced disruptions to visual input. Here, we investigated to what extent these conveyed metrics influence perceptual stability in human subjects with a target-displacement detection task. Subjects made saccades to targets located at different amplitudes (4°, 6°, or 8°) and directions (horizontal or vertical). During the saccade, the target disappeared and then reappeared at a shifted location either in the same direction or opposite to the movement vector. Subjects reported the target displacement direction, and from these reports we deter- mined the perceptual threshold for shift detection and estimate of target location. Our results indicate that the thresholds for all ampli- tudes and directions generally scaled with saccade amplitude. Addi- tionally, subjects on average produced hypometric saccades with an estimated CD gain ⬍1. Finally, we examined the contribution of different error signals to perceptual performance, the saccade error (movement-to-movement variability in saccade amplitude) and visual error (distance between the fovea and the shifted target location). Perceptual judgment was not influenced by the fluctuations in move- ment amplitude, and performance was largely the same across move- ment directions for different magnitudes of visual error. Importantly, subjects reported the correct direction of target displacement above chance level for very small visual errors (⬍0.75°), even when these errors were opposite the target-shift direction. Collectively, these results suggest that the CD-based compensatory mechanisms for visual disruptions are highly accurate and comparable for saccades with different metrics.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The effect of saccade metrics on the corollary discharge contribution to per- ceived eye location. J Neurophysiol 113: 3312–3322, 2015. First published March 11, 2015; doi:10.1152/jn.00771.2014.—Corollary discharge (CD) is hypothesized to provide the movement information (direction and amplitude) required to compensate for the saccade- induced disruptions to visual input. Here, we investigated to what extent these conveyed metrics influence perceptual stability in human subjects with a target-displacement detection task. Subjects made saccades to targets located at different amplitudes (4°, 6°, or 8°) and directions (horizontal or vertical). During the saccade, the target disappeared and then reappeared at a shifted location either in the same direction or opposite to the movement vector. Subjects reported the target displacement direction, and from these reports we deter- mined the perceptual threshold for shift detection and estimate of target location. Our results indicate that the thresholds for all ampli- tudes and directions generally scaled with saccade amplitude. Addi- tionally, subjects on average produced hypometric saccades with an estimated CD gain ⬍1. Finally, we examined the contribution of different error signals to perceptual performance, the saccade error (movement-to-movement variability in saccade amplitude) and visual error (distance between the fovea and the shifted target location). Perceptual judgment was not influenced by the fluctuations in move- ment amplitude, and performance was largely the same across move- ment directions for different magnitudes of visual error. Importantly, subjects reported the correct direction of target displacement above chance level for very small visual errors (⬍0.75°), even when these errors were opposite the target-shift direction. Collectively, these results suggest that the CD-based compensatory mechanisms for visual disruptions are highly accurate and comparable for saccades with different metrics. |
Carol J Y Bao; Cristina Rubino; Alisdair Taylor; Jason J S Barton The effects of homonymous hemianopia in experimental studies of alexia Journal Article Neuropsychologia, 70 , pp. 156–164, 2015. @article{Bao2015a, title = {The effects of homonymous hemianopia in experimental studies of alexia}, author = {Carol J Y Bao and Cristina Rubino and Alisdair Taylor and Jason J S Barton}, doi = {10.1016/j.neuropsychologia.2015.02.026}, year = {2015}, date = {2015-01-01}, journal = {Neuropsychologia}, volume = {70}, pages = {156--164}, publisher = {Elsevier}, abstract = {Pure alexia is characterized by an increased word-length effect in reading. However, this disorder is usually accompanied by right homonymous hemianopia, which itself can cause a mildly increased word-length effect. Some alexic studies have used hemianopic patients with modest word-length effects: it is not clear (a) whether they had pure alexia and (b) if not, whether their results could be explained by the field defect. Our goal was to determine if impairments in visual processing claimed to be related to alexia could be replicated in homonymous hemianopia alone. Twelve healthy subjects performed five experiments used in two prior studies of alexia, under both normal and simulated hemianopic conditions, using a gaze-contingent display generated by an eye-tracker. We replicated the increased word-length effect for reading time with right homonymous hemianopia, and showed a similar effect for a lexical decision task. Simulated hemianopia impaired scanning accuracy for letter or number strings, and slowed object part processing, though the effect of configuration was not greater under hemianopic viewing. Hemianopia impaired the identification of words whose letters appeared and disappeared sequentially on the screen, with better performance on a cumulative presentation in which the letters remained on the screen. The reporting of trigrams was less accurate with hemianopia, though syllabic structure did not influence the results. We conclude that some impairments that have been attributed to the processing defects underlying alexia may actually be due to right homonymous hemianopia. Our results underline the importance of considering the contribution of accompanying low-level visual impairments when studying high-level processes.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Pure alexia is characterized by an increased word-length effect in reading. However, this disorder is usually accompanied by right homonymous hemianopia, which itself can cause a mildly increased word-length effect. Some alexic studies have used hemianopic patients with modest word-length effects: it is not clear (a) whether they had pure alexia and (b) if not, whether their results could be explained by the field defect. Our goal was to determine if impairments in visual processing claimed to be related to alexia could be replicated in homonymous hemianopia alone. Twelve healthy subjects performed five experiments used in two prior studies of alexia, under both normal and simulated hemianopic conditions, using a gaze-contingent display generated by an eye-tracker. We replicated the increased word-length effect for reading time with right homonymous hemianopia, and showed a similar effect for a lexical decision task. Simulated hemianopia impaired scanning accuracy for letter or number strings, and slowed object part processing, though the effect of configuration was not greater under hemianopic viewing. Hemianopia impaired the identification of words whose letters appeared and disappeared sequentially on the screen, with better performance on a cumulative presentation in which the letters remained on the screen. The reporting of trigrams was less accurate with hemianopia, though syllabic structure did not influence the results. We conclude that some impairments that have been attributed to the processing defects underlying alexia may actually be due to right homonymous hemianopia. Our results underline the importance of considering the contribution of accompanying low-level visual impairments when studying high-level processes. |
Pinglei Bao; Christopher J Purington; Bosco S Tjan Using an achiasmic human visual system to quantify the relationship between the fMRI BOLD signal and neural response Journal Article eLife, 4 (NOVEMBER2015), pp. 1–21, 2015. @article{Bao2015b, title = {Using an achiasmic human visual system to quantify the relationship between the fMRI BOLD signal and neural response}, author = {Pinglei Bao and Christopher J Purington and Bosco S Tjan}, doi = {10.7554/eLife.09600}, year = {2015}, date = {2015-01-01}, journal = {eLife}, volume = {4}, number = {NOVEMBER2015}, pages = {1--21}, abstract = {Achiasma in humans causes gross mis-wiring of the retinal-fugal projection, resulting in overlapped cortical representations of left and right visual hemifields. We show that in areas V1-V3 this overlap is due to two co-located but non-interacting populations of neurons, each with a receptive field serving only one hemifield. Importantly, the two populations share the same local vascular control, resulting in a unique organization useful for quantifying the relationship between neural and fMRI BOLD responses without direct measurement of neural activity. Specifically, we can non-invasively double local neural responses by stimulating both neuronal populations with identical stimuli presented symmetrically across the vertical meridian to both visual hemifields, versus one population by stimulating in one hemifield. Measurements from a series of such doubling experiments show that the amplitude of BOLD response is proportional to approximately 0.5 power of the underlying neural response. Reanalyzing published data shows that this inferred relationship is general.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Achiasma in humans causes gross mis-wiring of the retinal-fugal projection, resulting in overlapped cortical representations of left and right visual hemifields. We show that in areas V1-V3 this overlap is due to two co-located but non-interacting populations of neurons, each with a receptive field serving only one hemifield. Importantly, the two populations share the same local vascular control, resulting in a unique organization useful for quantifying the relationship between neural and fMRI BOLD responses without direct measurement of neural activity. Specifically, we can non-invasively double local neural responses by stimulating both neuronal populations with identical stimuli presented symmetrically across the vertical meridian to both visual hemifields, versus one population by stimulating in one hemifield. Measurements from a series of such doubling experiments show that the amplitude of BOLD response is proportional to approximately 0.5 power of the underlying neural response. Reanalyzing published data shows that this inferred relationship is general. |
Bengi Baran; David Correll; Tessa C Vuper; Alexandra Morgan; Simon J Durrant; Dara S Manoach; Robert Stickgold Spared and impaired sleep-dependent memory consolidation in schizophrenia Journal Article Schizophrenia Research, 199 , pp. 83–89, 2018. @article{Baran2018, title = {Spared and impaired sleep-dependent memory consolidation in schizophrenia}, author = {Bengi Baran and David Correll and Tessa C Vuper and Alexandra Morgan and Simon J Durrant and Dara S Manoach and Robert Stickgold}, doi = {10.1016/j.schres.2018.04.019}, year = {2018}, date = {2018-01-01}, journal = {Schizophrenia Research}, volume = {199}, pages = {83--89}, publisher = {Elsevier B.V.}, abstract = {Objective: Cognitive deficits in schizophrenia are the strongest predictor of disability and effective treatment is lacking. This reflects our limited mechanistic understanding and consequent lack of treatment targets. In schizophrenia, impaired sleep-dependent memory consolidation correlates with reduced sleep spindle activity, suggesting sleep spindles as a potentially treatable mechanism. In the present study we investigated whether sleep-dependent memory consolidation deficits in schizophrenia are selective. Methods: Schizophrenia patients and healthy individuals performed three tasks that have been shownto undergo sleep-dependent consolidation: the Word Pair Task (verbal declarative memory), the Visual Discrimination Task (visuoperceptual procedural memory), and the Tone Task (statistical learning). Memory consolidation was tested 24 h later, after a night of sleep. Results: Compared with controls, schizophrenia patients showed reduced overnight consolidation ofword pair learning. In contrast, both groups showed similar significant overnight consolidation of visuoperceptual procedural memory. Neither group showed overnight consolidation of statistical learning. Conclusion: The present findings extend the known deficits in sleep-dependent memory consolidation in schizophrenia to verbal declarative memory, a core, disabling cognitive deficit. In contrast, visuoperceptual procedural memorywas spared. These findings support the hypothesis that sleep-dependent memory consolidation deficits in schizophrenia are selective, possibly limited to tasks that rely on spindles. These findings reinforce the importance ofdeficient sleep-dependent memory consolidation among the cognitive deficits ofschizophrenia and suggest sleep physiology as a potentially treatable mechanism.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Objective: Cognitive deficits in schizophrenia are the strongest predictor of disability and effective treatment is lacking. This reflects our limited mechanistic understanding and consequent lack of treatment targets. In schizophrenia, impaired sleep-dependent memory consolidation correlates with reduced sleep spindle activity, suggesting sleep spindles as a potentially treatable mechanism. In the present study we investigated whether sleep-dependent memory consolidation deficits in schizophrenia are selective. Methods: Schizophrenia patients and healthy individuals performed three tasks that have been shownto undergo sleep-dependent consolidation: the Word Pair Task (verbal declarative memory), the Visual Discrimination Task (visuoperceptual procedural memory), and the Tone Task (statistical learning). Memory consolidation was tested 24 h later, after a night of sleep. Results: Compared with controls, schizophrenia patients showed reduced overnight consolidation ofword pair learning. In contrast, both groups showed similar significant overnight consolidation of visuoperceptual procedural memory. Neither group showed overnight consolidation of statistical learning. Conclusion: The present findings extend the known deficits in sleep-dependent memory consolidation in schizophrenia to verbal declarative memory, a core, disabling cognitive deficit. In contrast, visuoperceptual procedural memorywas spared. These findings support the hypothesis that sleep-dependent memory consolidation deficits in schizophrenia are selective, possibly limited to tasks that rely on spindles. These findings reinforce the importance ofdeficient sleep-dependent memory consolidation among the cognitive deficits ofschizophrenia and suggest sleep physiology as a potentially treatable mechanism. |
Niraj Barot; Rebecca J McLean; Irene Gottlob; Frank A Proudlock Reading performance in infantile nystagmus Journal Article Ophthalmology, 120 (6), pp. 1232–1238, 2013. @article{Barot2013, title = {Reading performance in infantile nystagmus}, author = {Niraj Barot and Rebecca J McLean and Irene Gottlob and Frank A Proudlock}, doi = {10.1016/j.ophtha.2012.11.032}, year = {2013}, date = {2013-01-01}, journal = {Ophthalmology}, volume = {120}, number = {6}, pages = {1232--1238}, publisher = {Elsevier Inc.}, abstract = {Objective: To characterize reading deficits in infantile nystagmus (IN), to determine optimal font sizes for reading in IN, and to investigate whether visual acuity (VA) and severity of nystagmus are good indicators of reading performance in IN. Design: Prospective cross-sectional study. Participants and Controls: Seventy-one participants with IN (37 idiopathic, 34 with albinism) and 20 age-matched controls. Methods: Reading performance was assessed using Radner reading charts and was compared with near logarithm of the minimum angle of resolution (logMAR) VA, nystagmus intensity, and foveation characteristics as quantified using eye movement recordings. Main Outcome Measures: Reading acuity (smallest readable font size), maximum reading speed, critical print size (font size below which reading is suboptimal), near logMAR VA, nystagmus intensity, and foveation characteristics (using the eXpanded Nystagmus Acuity Function). Results: Using optimal reading conditions, maximum reading speeds were 18.8% slower in albinism and 14.7% slower in idiopathic IN patients compared with controls. Reading acuities were significantly worse (Ptextless0.001) in IN patients compared with controls. Also, the range of font sizes over which reading speeds were less than the optimum were much larger in IN patients compared with controls (Ptextless0.001). Reading acuity was correlated strongly to near VA (r2= 0.74 albinism}, keywords = {}, pubstate = {published}, tppubtype = {article} } Objective: To characterize reading deficits in infantile nystagmus (IN), to determine optimal font sizes for reading in IN, and to investigate whether visual acuity (VA) and severity of nystagmus are good indicators of reading performance in IN. Design: Prospective cross-sectional study. Participants and Controls: Seventy-one participants with IN (37 idiopathic, 34 with albinism) and 20 age-matched controls. Methods: Reading performance was assessed using Radner reading charts and was compared with near logarithm of the minimum angle of resolution (logMAR) VA, nystagmus intensity, and foveation characteristics as quantified using eye movement recordings. Main Outcome Measures: Reading acuity (smallest readable font size), maximum reading speed, critical print size (font size below which reading is suboptimal), near logMAR VA, nystagmus intensity, and foveation characteristics (using the eXpanded Nystagmus Acuity Function). Results: Using optimal reading conditions, maximum reading speeds were 18.8% slower in albinism and 14.7% slower in idiopathic IN patients compared with controls. Reading acuities were significantly worse (Ptextless0.001) in IN patients compared with controls. Also, the range of font sizes over which reading speeds were less than the optimum were much larger in IN patients compared with controls (Ptextless0.001). Reading acuity was correlated strongly to near VA (r2= 0.74 albinism |
Maria J Barraza-Bernal; Katharina Rifai; Siegfried Wahl Transfer of an induced preferred retinal locus of fixation to everyday life visual tasks Journal Article Journal of Vision, 17 (14), pp. 2, 2017. @article{Barraza-Bernal2017a, title = {Transfer of an induced preferred retinal locus of fixation to everyday life visual tasks}, author = {Maria J Barraza-Bernal and Katharina Rifai and Siegfried Wahl}, doi = {10.1167/17.14.2}, year = {2017}, date = {2017-01-01}, journal = {Journal of Vision}, volume = {17}, number = {14}, pages = {2}, abstract = {Subjects develop a preferred retinal locus of fixation (PRL) under simulation of central scotoma. If systematic relocations are applied to the stimulus position, PRLs manifest at a location in favor of the stimulus relocation. The present study investigates whether the induced PRL is transferred to important visual tasks in daily life, namely pursuit eye movements, signage reading, and text reading. Fifteen subjects with normal sight participated in the study. To develop a PRL, all subjects underwent a scotoma simulation in a prior study, where five subjects were trained to develop the PRL in the left hemifield, five different subjects on the right hemifield, and the remaining five subjects could naturally chose the PRL location. The position of this PRL was used as baseline. Under central scotoma simulation, subjects performed a pursuit task, a signage reading task, and a reading-text task. In addition, retention of the behavior was also studied. Results showed that the PRL position was transferred to the pursuit task and that the vertical location of the PRL was maintained on the text reading task. However, when reading signage, a function-driven change in PRL location was observed. In addition, retention of the PRL position was observed over weeks and months. These results indicate that PRL positions can be induced and may further transferred to everyday life visual tasks, without hindering function-driven changes in PRL position.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Subjects develop a preferred retinal locus of fixation (PRL) under simulation of central scotoma. If systematic relocations are applied to the stimulus position, PRLs manifest at a location in favor of the stimulus relocation. The present study investigates whether the induced PRL is transferred to important visual tasks in daily life, namely pursuit eye movements, signage reading, and text reading. Fifteen subjects with normal sight participated in the study. To develop a PRL, all subjects underwent a scotoma simulation in a prior study, where five subjects were trained to develop the PRL in the left hemifield, five different subjects on the right hemifield, and the remaining five subjects could naturally chose the PRL location. The position of this PRL was used as baseline. Under central scotoma simulation, subjects performed a pursuit task, a signage reading task, and a reading-text task. In addition, retention of the behavior was also studied. Results showed that the PRL position was transferred to the pursuit task and that the vertical location of the PRL was maintained on the text reading task. However, when reading signage, a function-driven change in PRL location was observed. In addition, retention of the PRL position was observed over weeks and months. These results indicate that PRL positions can be induced and may further transferred to everyday life visual tasks, without hindering function-driven changes in PRL position. |
Maria J Barraza-Bernal; Katharina Rifai; Siegfried Wahl A preferred retinal location of fixation can be induced when systematic stimulus relocations are applied Journal Article Journal of Vision, 17 (2), pp. 1–13, 2017. @article{Barraza-Bernal2017b, title = {A preferred retinal location of fixation can be induced when systematic stimulus relocations are applied}, author = {Maria J Barraza-Bernal and Katharina Rifai and Siegfried Wahl}, doi = {10.1167/17.2.11}, year = {2017}, date = {2017-01-01}, journal = {Journal of Vision}, volume = {17}, number = {2}, pages = {1--13}, abstract = {Patients with central vision loss obtain visual information by fixating on an object eccentrically with a preferred retinal locus of fixation (PRL). Patients do not always choose the most efficient PRL position, and as a consequence, visual performance is not always fully exploited. This study investigates whether PRLs can be induced by applying systematic stimulus relocations. The PRL was trained using a central scotoma simulation in 15 healthy subjects. They performed different visual tasks during four sessions, after which their reading performance was evaluated. In five subjects the stimulus was relocated to the left hemifield whenever a saccade would place the stimulus on the opposite hemifield. In five different subjects the relocation was inversed: The stimulus was located in the right hemifield. The relocation was 7.5° of visual angle and it was applied horizontally. Five additional subjects naturally chose the PRL location. They were used as the control group to evaluate the development of a PRL. After training, subjects performed visual search tasks on static stimuli. Evaluation after training showed that systematic stimulus relocations can be used to influence the development of the PRL. These results might be significant for the development of training strategies for the visually impaired.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Patients with central vision loss obtain visual information by fixating on an object eccentrically with a preferred retinal locus of fixation (PRL). Patients do not always choose the most efficient PRL position, and as a consequence, visual performance is not always fully exploited. This study investigates whether PRLs can be induced by applying systematic stimulus relocations. The PRL was trained using a central scotoma simulation in 15 healthy subjects. They performed different visual tasks during four sessions, after which their reading performance was evaluated. In five subjects the stimulus was relocated to the left hemifield whenever a saccade would place the stimulus on the opposite hemifield. In five different subjects the relocation was inversed: The stimulus was located in the right hemifield. The relocation was 7.5° of visual angle and it was applied horizontally. Five additional subjects naturally chose the PRL location. They were used as the control group to evaluate the development of a PRL. After training, subjects performed visual search tasks on static stimuli. Evaluation after training showed that systematic stimulus relocations can be used to influence the development of the PRL. These results might be significant for the development of training strategies for the visually impaired. |
Maria J Barraza-Bernal; Katharina Rifai; Siegfried Wahl The retinal locus of fixation in simulations of progressing central scotomas Journal Article Journal of Vision, 18 (1), pp. 1–12, 2018. @article{Barraza-Bernal2018, title = {The retinal locus of fixation in simulations of progressing central scotomas}, author = {Maria J Barraza-Bernal and Katharina Rifai and Siegfried Wahl}, doi = {10.1167/18.1.7}, year = {2018}, date = {2018-01-01}, journal = {Journal of Vision}, volume = {18}, number = {1}, pages = {1--12}, abstract = {Patients with central scotoma use a preferred retinal locus (PRL) of fixation to perform visual tasks. Some of the conditions that cause central scotoma are progressive, and as a consequence, the PRL needs to be adjusted throughout the progression. The present study investigates the peripheral locus of fixation in subjects under a simulation of progressive central scotoma. Five normally sighted subjects participated in the study. A foveally centered mask of varying size was presented to simulate the scotoma. Initially, subjects developed a peripheral locus of fixation under simulation of a 68 scotoma, which was used as a baseline. The progression was simulated in two separate conditions: a gradual progression and an abrupt progression. In the gradual progression, the diameter of the scotoma increased by a fixed amount of either 18 or 28 of visual angle, thus scotomas of 88, 108, and 118 of visual angle were simulated. In the abrupt progression, the diameter was adjusted individually to span the area of the visual field used by the current peripheral locus of fixation. Subjects located the peripheral locus of fixation along the same meridian under simulation of scotoma progression. Furthermore, no differences between the fixation stability of the baseline locus of fixation and the incremental progression locus of fixation were found whereas, in abrupt progression, the fixation stability decreased significantly. These results provide first insight into fixation behavior in a progressive scotoma and may contribute to the development of training tools for patients with progressive central maculopathies.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Patients with central scotoma use a preferred retinal locus (PRL) of fixation to perform visual tasks. Some of the conditions that cause central scotoma are progressive, and as a consequence, the PRL needs to be adjusted throughout the progression. The present study investigates the peripheral locus of fixation in subjects under a simulation of progressive central scotoma. Five normally sighted subjects participated in the study. A foveally centered mask of varying size was presented to simulate the scotoma. Initially, subjects developed a peripheral locus of fixation under simulation of a 68 scotoma, which was used as a baseline. The progression was simulated in two separate conditions: a gradual progression and an abrupt progression. In the gradual progression, the diameter of the scotoma increased by a fixed amount of either 18 or 28 of visual angle, thus scotomas of 88, 108, and 118 of visual angle were simulated. In the abrupt progression, the diameter was adjusted individually to span the area of the visual field used by the current peripheral locus of fixation. Subjects located the peripheral locus of fixation along the same meridian under simulation of scotoma progression. Furthermore, no differences between the fixation stability of the baseline locus of fixation and the incremental progression locus of fixation were found whereas, in abrupt progression, the fixation stability decreased significantly. These results provide first insight into fixation behavior in a progressive scotoma and may contribute to the development of training tools for patients with progressive central maculopathies. |
Pablo A Barrionuevo; Nathaniel Nicandro; Jason J McAnany; Andrew J Zele; Paul Gamlin; Dingcai Cao Assessing rod, cone, and melanopsin contributions to human pupil flicker responses Journal Article Investigative Ophthalmology & Visual Science, 55 (2), pp. 719–727, 2014. @article{Barrionuevo2014, title = {Assessing rod, cone, and melanopsin contributions to human pupil flicker responses}, author = {Pablo A Barrionuevo and Nathaniel Nicandro and Jason J McAnany and Andrew J Zele and Paul Gamlin and Dingcai Cao}, doi = {10.1167/iovs.13-13252}, year = {2014}, date = {2014-01-01}, journal = {Investigative Ophthalmology & Visual Science}, volume = {55}, number = {2}, pages = {719--727}, abstract = {PURPOSE: We determined the relative contributions of rods, cones, and melanopsin to pupil responses in humans using temporal sinusoidal stimulation for light levels spanning the low mesopic to photopic range. METHODS: A four-primary Ganzfeld photostimulator controlled flicker stimulations at seven light levels (-2.7 to 2 log cd/m(2)) and five frequencies (0.5-8 Hz). Pupil diameter was measured using a high-resolution eye tracker. Three kinds of sinusoidal photoreceptor modulations were generated using silent substitution: rod modulation, cone modulation, and combined rod and cone modulation in phase (experiment 1) or cone phase shifted (experiment 2) from a fixed rod phase. The melanopsin excitation was computed for each condition. A vector sum model was used to estimate the relative contribution of rods, cones, and melanopsin to the pupil response. RESULTS: From experiment 1, the pupil frequency response peaked at 1 Hz at two mesopic light levels for the three modulation conditions. Analyzing the rod-cone phase difference for the combined modulations (experiment 2) identified a V-shaped response amplitude with a minimum between 135° and 180°. The pupil response phases increased as cone modulation phase increased. The pupil amplitude increased with increasing light level for cone, and combined (in-phase rod and cone) modulation, but not for the rod modulation. CONCLUSIONS: These results demonstrate that cone- and rod-pathway contributions are more predominant than melanopsin contribution to the phasic pupil response. The combined rod, cone, and melanopsin inputs to the phasic state of the pupil light reflex follow linear summation.}, keywords = {}, pubstate = {published}, tppubtype = {article} } PURPOSE: We determined the relative contributions of rods, cones, and melanopsin to pupil responses in humans using temporal sinusoidal stimulation for light levels spanning the low mesopic to photopic range. METHODS: A four-primary Ganzfeld photostimulator controlled flicker stimulations at seven light levels (-2.7 to 2 log cd/m(2)) and five frequencies (0.5-8 Hz). Pupil diameter was measured using a high-resolution eye tracker. Three kinds of sinusoidal photoreceptor modulations were generated using silent substitution: rod modulation, cone modulation, and combined rod and cone modulation in phase (experiment 1) or cone phase shifted (experiment 2) from a fixed rod phase. The melanopsin excitation was computed for each condition. A vector sum model was used to estimate the relative contribution of rods, cones, and melanopsin to the pupil response. RESULTS: From experiment 1, the pupil frequency response peaked at 1 Hz at two mesopic light levels for the three modulation conditions. Analyzing the rod-cone phase difference for the combined modulations (experiment 2) identified a V-shaped response amplitude with a minimum between 135° and 180°. The pupil response phases increased as cone modulation phase increased. The pupil amplitude increased with increasing light level for cone, and combined (in-phase rod and cone) modulation, but not for the rod modulation. CONCLUSIONS: These results demonstrate that cone- and rod-pathway contributions are more predominant than melanopsin contribution to the phasic pupil response. The combined rod, cone, and melanopsin inputs to the phasic state of the pupil light reflex follow linear summation. |
Pablo A Barrionuevo; Dingcai Cao Luminance and chromatic signals interact differently with melanopsin activation to control the pupil light response Journal Article Journal of Vision, 16 (11), pp. 29, 2016. @article{Barrionuevo2016, title = {Luminance and chromatic signals interact differently with melanopsin activation to control the pupil light response}, author = {Pablo A Barrionuevo and Dingcai Cao}, doi = {10.1167/16.11.29}, year = {2016}, date = {2016-01-01}, journal = {Journal of Vision}, volume = {16}, number = {11}, pages = {29}, abstract = {Intrinsically photosensitive retinal ganglion cells (ipRGCs) express the photopigment melanopsin. These cells receive afferent inputs from rods and cones, which provide inputs to the postreceptoral visual pathways. It is unknown, however, how melanopsin activation is integrated with postreceptoral signals to control the pupillary light reflex. This study reports human flicker pupillary responses measured using stimuli generated with a five-primary photostimulator that selectively modulated melanopsin, rod, S-, M-, and L-cone excitations in isolation, or in combination to produce postreceptoral signals. We first analyzed the light adaptation behavior of melanopsin activation and rod and cones signals. Second, we determined how melanopsin is integrated with postreceptoral signals by testing with cone luminance, chromatic blue-yellow, and chromatic red-green stimuli that were processed by magnocellular (MC), koniocellular (KC), and parvocellular (PC) pathways, respectively. A combined rod and melanopsin response was also measured. The relative phase of the postreceptoral signals was varied with respect to the melanopsin phase. The results showed that light adaptation behavior for all conditions was weaker than typical Weber adaptation. Melanopsin activation combined linearly with luminance, S-cone, and rod inputs, suggesting the locus of integration with MC and KC signals was retinal. The melanopsin contribution to phasic pupil responses was lower than luminance contributions, but much higher than S-cone contributions. Chromatic red-green modulation interacted with melanopsin activation nonlinearly as described by a "winner-takes-all" process, suggesting the integration with PC signals might be mediated by a postretinal site.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Intrinsically photosensitive retinal ganglion cells (ipRGCs) express the photopigment melanopsin. These cells receive afferent inputs from rods and cones, which provide inputs to the postreceptoral visual pathways. It is unknown, however, how melanopsin activation is integrated with postreceptoral signals to control the pupillary light reflex. This study reports human flicker pupillary responses measured using stimuli generated with a five-primary photostimulator that selectively modulated melanopsin, rod, S-, M-, and L-cone excitations in isolation, or in combination to produce postreceptoral signals. We first analyzed the light adaptation behavior of melanopsin activation and rod and cones signals. Second, we determined how melanopsin is integrated with postreceptoral signals by testing with cone luminance, chromatic blue-yellow, and chromatic red-green stimuli that were processed by magnocellular (MC), koniocellular (KC), and parvocellular (PC) pathways, respectively. A combined rod and melanopsin response was also measured. The relative phase of the postreceptoral signals was varied with respect to the melanopsin phase. The results showed that light adaptation behavior for all conditions was weaker than typical Weber adaptation. Melanopsin activation combined linearly with luminance, S-cone, and rod inputs, suggesting the locus of integration with MC and KC signals was retinal. The melanopsin contribution to phasic pupil responses was lower than luminance contributions, but much higher than S-cone contributions. Chromatic red-green modulation interacted with melanopsin activation nonlinearly as described by a "winner-takes-all" process, suggesting the integration with PC signals might be mediated by a postretinal site. |
Sarah Bate; Catherine Haslam; Jeremy J Tree; Timothy L Hodgson Evidence of an eye movement-based memory effect in congenital prosopagnosia Journal Article Cortex, 44 (7), pp. 806–819, 2008. @article{Bate2008, title = {Evidence of an eye movement-based memory effect in congenital prosopagnosia}, author = {Sarah Bate and Catherine Haslam and Jeremy J Tree and Timothy L Hodgson}, doi = {10.1016/j.cortex.2007.02.004}, year = {2008}, date = {2008-01-01}, journal = {Cortex}, volume = {44}, number = {7}, pages = {806--819}, abstract = {While extensive work has examined the role of covert recognition in acquired prosopagnosia, little attention has been directed to this process in the congenital form of the disorder. Indeed, evidence of covert recognition has only been demonstrated in one congenital case in which autonomic measures provided evidence of recognition (Jones and Tranel, 2001), whereas two investigations using behavioural indicators failed to demonstrate the effect (de Haan and Campbell, 1991; Bentin et al., 1999). In this paper, we use a behavioural indicator, an "eye movement-based memory effect" (Althoff and Cohen, 1999), to provide evidence of covert recognition in congenital prosopagnosia. In an initial experiment, we examined viewing strategies elicited to famous and novel faces in control participants, and found fewer fixations and reduced regional sampling for famous compared to novel faces. In a second experiment, we examined the same processes in a patient with congenital prosopagnosia (AA), and found some evidence of an eye movement-based memory effect regardless of his recognition accuracy. Finally, we examined whether a difference in scanning strategy was evident for those famous faces AA failed to explicitly recognise, and again found evidence of reduced sampling for famous faces. We use these findings to (a) provide evidence of intact structural representations in a case of congenital prosopagnosia, and (b) to suggest that covert recognition can be demonstrated using behavioural indicators in this disorder.}, keywords = {}, pubstate = {published}, tppubtype = {article} } While extensive work has examined the role of covert recognition in acquired prosopagnosia, little attention has been directed to this process in the congenital form of the disorder. Indeed, evidence of covert recognition has only been demonstrated in one congenital case in which autonomic measures provided evidence of recognition (Jones and Tranel, 2001), whereas two investigations using behavioural indicators failed to demonstrate the effect (de Haan and Campbell, 1991; Bentin et al., 1999). In this paper, we use a behavioural indicator, an "eye movement-based memory effect" (Althoff and Cohen, 1999), to provide evidence of covert recognition in congenital prosopagnosia. In an initial experiment, we examined viewing strategies elicited to famous and novel faces in control participants, and found fewer fixations and reduced regional sampling for famous compared to novel faces. In a second experiment, we examined the same processes in a patient with congenital prosopagnosia (AA), and found some evidence of an eye movement-based memory effect regardless of his recognition accuracy. Finally, we examined whether a difference in scanning strategy was evident for those famous faces AA failed to explicitly recognise, and again found evidence of reduced sampling for famous faces. We use these findings to (a) provide evidence of intact structural representations in a case of congenital prosopagnosia, and (b) to suggest that covert recognition can be demonstrated using behavioural indicators in this disorder. |
Sarah Bate; Catherine Haslam; Ashok Jansari; Timothy L Hodgson Covert face recognition relies on affective valence in congenital prosopagnosia Journal Article Cognitive Neuropsychology, 26 (4), pp. 391–411, 2009. @article{Bate2009b, title = {Covert face recognition relies on affective valence in congenital prosopagnosia}, author = {Sarah Bate and Catherine Haslam and Ashok Jansari and Timothy L Hodgson}, doi = {10.1080/02643290903175004}, year = {2009}, date = {2009-01-01}, journal = {Cognitive Neuropsychology}, volume = {26}, number = {4}, pages = {391--411}, abstract = {Dominant accounts of covert recognition in prosopagnosia assume subthreshold activation of face representations created prior to onset of the disorder. Yet, such accounts cannot explain covert recognition in congenital prosopagnosia, where the impairment is present from birth. Alternatively, covert recognition may rely on affective valence, yet no study has explored this possibility. The current study addressed this issue in 3 individuals with congenital prosopagnosia, using measures of the scanpath to indicate recognition. Participants were asked to memorize 30 faces paired with descriptions of aggressive, nice, or neutral behaviours. In a later recognition test, eye movements were monitored while participants discriminated studied from novel faces. Sampling was reduced for studied--nice compared to studied--aggressive faces, and performance for studied--neutral and novel faces fell between these two conditions. This pattern of findings suggests that (a) positive emotion can facilitate processing in prosopagnosia, and (b) covert recognition may rely on emotional valence rather than familiarity.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Dominant accounts of covert recognition in prosopagnosia assume subthreshold activation of face representations created prior to onset of the disorder. Yet, such accounts cannot explain covert recognition in congenital prosopagnosia, where the impairment is present from birth. Alternatively, covert recognition may rely on affective valence, yet no study has explored this possibility. The current study addressed this issue in 3 individuals with congenital prosopagnosia, using measures of the scanpath to indicate recognition. Participants were asked to memorize 30 faces paired with descriptions of aggressive, nice, or neutral behaviours. In a later recognition test, eye movements were monitored while participants discriminated studied from novel faces. Sampling was reduced for studied--nice compared to studied--aggressive faces, and performance for studied--neutral and novel faces fell between these two conditions. This pattern of findings suggests that (a) positive emotion can facilitate processing in prosopagnosia, and (b) covert recognition may rely on emotional valence rather than familiarity. |
Sarah Bate; Rachel Bennetts; Joseph A Mole; James A Ainge; Nicola J Gregory; Anna K Bobak; Amanda Bussunt Rehabilitation of face-processing skills in an adolescent with prosopagnosia: Evaluation of an online perceptual training programme Journal Article Neuropsychological Rehabilitation, 25 (5), pp. 733–762, 2015. @article{Bate2015, title = {Rehabilitation of face-processing skills in an adolescent with prosopagnosia: Evaluation of an online perceptual training programme}, author = {Sarah Bate and Rachel Bennetts and Joseph A Mole and James A Ainge and Nicola J Gregory and Anna K Bobak and Amanda Bussunt}, doi = {10.1080/09602011.2014.973886}, year = {2015}, date = {2015-01-01}, journal = {Neuropsychological Rehabilitation}, volume = {25}, number = {5}, pages = {733--762}, abstract = {In this paper we describe the case of EM, a female adolescent who acquired prosopagnosia following encephalitis at the age of eight. Initial neuropsychological and eye-movement investigations indicated that EM had profound difficulties in face perception as well as face recognition. EM underwent 14 weeks of perceptual training in an online programme that attempted to improve her ability to make fine-grained discriminations between faces. Following training, EM's face perception skills had improved, and the effect generalised to untrained faces. Eye-movement analyses also indicated that EM spent more time viewing the inner facial features post-training. Examination of EM's face recognition skills revealed an improvement in her recognition of personally-known faces when presented in a laboratory-based test, although the same gains were not noted in her everyday experiences with these faces. In addition, EM did not improve on a test assessing the recognition of newly encoded faces. One month after training, EM had maintained the improvement on the eye-tracking test, and to a lesser extent, her performance on the familiar faces test. This pattern of findings is interpreted as promising evidence that the programme can improve face perception skills, and with some adjustments, may at least partially improve face recognition skills.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this paper we describe the case of EM, a female adolescent who acquired prosopagnosia following encephalitis at the age of eight. Initial neuropsychological and eye-movement investigations indicated that EM had profound difficulties in face perception as well as face recognition. EM underwent 14 weeks of perceptual training in an online programme that attempted to improve her ability to make fine-grained discriminations between faces. Following training, EM's face perception skills had improved, and the effect generalised to untrained faces. Eye-movement analyses also indicated that EM spent more time viewing the inner facial features post-training. Examination of EM's face recognition skills revealed an improvement in her recognition of personally-known faces when presented in a laboratory-based test, although the same gains were not noted in her everyday experiences with these faces. In addition, EM did not improve on a test assessing the recognition of newly encoded faces. One month after training, EM had maintained the improvement on the eye-tracking test, and to a lesser extent, her performance on the familiar faces test. This pattern of findings is interpreted as promising evidence that the programme can improve face perception skills, and with some adjustments, may at least partially improve face recognition skills. |
Louise Beattie; Markus Bindemann; Simon D Kyle; Stephany M Biello Attention to beds in natural scenes by observers with insomnia symptoms Journal Article Behaviour Research and Therapy, 92 , pp. 51–56, 2017. @article{Beattie2017, title = {Attention to beds in natural scenes by observers with insomnia symptoms}, author = {Louise Beattie and Markus Bindemann and Simon D Kyle and Stephany M Biello}, doi = {10.1016/j.brat.2017.02.001}, year = {2017}, date = {2017-01-01}, journal = {Behaviour Research and Therapy}, volume = {92}, pages = {51--56}, publisher = {Elsevier Ltd}, abstract = {Attention biases to sleep-related stimuli are held to play a key role in the development and maintenance of insomnia, but such biases have only been shown with controlled visual displays. This study investigated whether observers with insomnia symptoms allocate attention to sleep-related items in natural scenes, by recording eye movements during free-viewing of bedrooms. Participants with insomnia symptoms and normal sleepers were matched in their visual exploration of these scenes, and there was no evidence that the attention of those with insomnia symptoms was captured more quickly by sleep-related stimuli than that of normal sleepers. However, the insomnia group fixated bed regions on more trials and, once fixated on a bed, also remained there for longer. These findings indicate that sleep stimuli are particularly effective in retaining visual attention in complex natural scenes.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Attention biases to sleep-related stimuli are held to play a key role in the development and maintenance of insomnia, but such biases have only been shown with controlled visual displays. This study investigated whether observers with insomnia symptoms allocate attention to sleep-related items in natural scenes, by recording eye movements during free-viewing of bedrooms. Participants with insomnia symptoms and normal sleepers were matched in their visual exploration of these scenes, and there was no evidence that the attention of those with insomnia symptoms was captured more quickly by sleep-related stimuli than that of normal sleepers. However, the insomnia group fixated bed regions on more trials and, once fixated on a bed, also remained there for longer. These findings indicate that sleep stimuli are particularly effective in retaining visual attention in complex natural scenes. |
Elizabeth H Beck; Anthony A Amato; Steven A Greenberg; Elizabeth H Beck Improvement of internuclear ophthalmoparesis in multiple sclerosis with dalfampridine Journal Article Neurology, 83 , pp. 192–194, 2014. @article{Beck2014, title = {Improvement of internuclear ophthalmoparesis in multiple sclerosis with dalfampridine}, author = {Elizabeth H Beck and Anthony A Amato and Steven A Greenberg and Elizabeth H Beck}, doi = {10.1212/WNL.0000000000000546}, year = {2014}, date = {2014-01-01}, journal = {Neurology}, volume = {83}, pages = {192--194}, abstract = {Internuclear ophthalmoparesis (INO) in multiple sclerosis (MS) is due to demyelination of the medial longitudinal fasciculus (MLF) and provides an acces- sible model for studying consequences of raised body temperature and fatigue on central demyelination.1,2 Prompted by one of our patient's report of vision improvement after initiating dalfampridine, a potas- sium channel blocker prescribed for gait impairment,3 we measured this drug's effects on 3 patients with MS with bilateral INO. All showed changes in horizontal saccadic conjugacy consistent with improved trans- mission of the neural pulse responsible for adducting movements.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Internuclear ophthalmoparesis (INO) in multiple sclerosis (MS) is due to demyelination of the medial longitudinal fasciculus (MLF) and provides an acces- sible model for studying consequences of raised body temperature and fatigue on central demyelination.1,2 Prompted by one of our patient's report of vision improvement after initiating dalfampridine, a potas- sium channel blocker prescribed for gait impairment,3 we measured this drug's effects on 3 patients with MS with bilateral INO. All showed changes in horizontal saccadic conjugacy consistent with improved trans- mission of the neural pulse responsible for adducting movements. |
Jeffrey S Bedwell; Christopher C Spencer; Chi C Chan; Pamela D Butler; Pejman Sehatpour; Joseph Schmidt The P1 visual-evoked potential, red light, and transdiagnostic psychiatric symptoms Journal Article Brain Research, 1687 , pp. 144–154, 2018. @article{Bedwell2018, title = {The P1 visual-evoked potential, red light, and transdiagnostic psychiatric symptoms}, author = {Jeffrey S Bedwell and Christopher C Spencer and Chi C Chan and Pamela D Butler and Pejman Sehatpour and Joseph Schmidt}, doi = {10.1016/j.brainres.2018.03.002}, year = {2018}, date = {2018-01-01}, journal = {Brain Research}, volume = {1687}, pages = {144--154}, publisher = {Elsevier B.V.}, abstract = {A reduced P1 visual-evoked potential amplitude has been reported across several psychiatric disorders, including schizophrenia-spectrum, bipolar, and depressive disorders. In addition, a difference in P1 amplitude change to a red background compared to its opponent color, green, has been found in schizophrenia-spectrum samples. The current study examined whether specific psychiatric symptoms that related to these P1 abnormalities in earlier studies would be replicated when using a broad transdiagnostic sample. The final sample consisted of 135 participants: 26 with bipolar disorders, 25 with schizophrenia-spectrum disorders, 19 with unipolar depression, 62 with no current psychiatric disorder, and 3 with disorders in other categories. Low (8%) and high (64%) contrast check arrays were presented on gray, green, and red background conditions during electroencephalogram, while an eye tracker monitored visual fixation on the stimuli. Linear regressions across the entire sample (N = 135) found that greater severity of both clinician-rated and self-reported delusions/magical thinking correlated with a reduced P1 amplitude on the low contrast gray (neutral) background condition. In addition, across the entire sample, higher self-reported constricted affect was associated with a larger decrease in P1 amplitude (averaged across contrast conditions) to the red, compared to green, background. All relationships remained statistically significant after covarying for diagnostic class, suggesting that they are relatively transdiagnostic in nature. These findings indicate that early visual processing abnormalities may be more directly related to specific transdiagnostic symptoms such as delusions and constricted affect rather than specific psychiatric diagnoses or broad symptom factor scales.}, keywords = {}, pubstate = {published}, tppubtype = {article} } A reduced P1 visual-evoked potential amplitude has been reported across several psychiatric disorders, including schizophrenia-spectrum, bipolar, and depressive disorders. In addition, a difference in P1 amplitude change to a red background compared to its opponent color, green, has been found in schizophrenia-spectrum samples. The current study examined whether specific psychiatric symptoms that related to these P1 abnormalities in earlier studies would be replicated when using a broad transdiagnostic sample. The final sample consisted of 135 participants: 26 with bipolar disorders, 25 with schizophrenia-spectrum disorders, 19 with unipolar depression, 62 with no current psychiatric disorder, and 3 with disorders in other categories. Low (8%) and high (64%) contrast check arrays were presented on gray, green, and red background conditions during electroencephalogram, while an eye tracker monitored visual fixation on the stimuli. Linear regressions across the entire sample (N = 135) found that greater severity of both clinician-rated and self-reported delusions/magical thinking correlated with a reduced P1 amplitude on the low contrast gray (neutral) background condition. In addition, across the entire sample, higher self-reported constricted affect was associated with a larger decrease in P1 amplitude (averaged across contrast conditions) to the red, compared to green, background. All relationships remained statistically significant after covarying for diagnostic class, suggesting that they are relatively transdiagnostic in nature. These findings indicate that early visual processing abnormalities may be more directly related to specific transdiagnostic symptoms such as delusions and constricted affect rather than specific psychiatric diagnoses or broad symptom factor scales. |
Sara A Beedie; Philip J Benson; Ina Giegling; Dan Rujescu; David M St. Clair Smooth pursuit and visual scanpaths: Independence of two candidate oculomotor risk markers for schizophrenia Journal Article The World Journal of Biological Psychiatry, 13 (3), pp. 200–210, 2012. @article{Beedie2012, title = {Smooth pursuit and visual scanpaths: Independence of two candidate oculomotor risk markers for schizophrenia}, author = {Sara A Beedie and Philip J Benson and Ina Giegling and Dan Rujescu and David M {St. Clair}}, doi = {10.3109/15622975.2011.566628}, year = {2012}, date = {2012-01-01}, journal = {The World Journal of Biological Psychiatry}, volume = {13}, number = {3}, pages = {200--210}, abstract = {OBJECTIVES: Smooth pursuit and visual scanpath deficits are candidate trait markers for schizophrenia. It is not clear whether eye tracking dysfunction (ETD) and atypical scanpath behaviour are the product of the same underlying neurobiological processes. We have examined co-occurrence of ETD and scanpath disturbance in individuals with schizophrenia and healthy volunteers. METHODS: Eye movements of individuals with schizophrenia (N = 96) and non-clinical age-matched comparison participants (N = 100) were recorded using non-invasive infrared oculography during smooth pursuit in both predictable (horizontal sinusoid) and less predictable (Lissajous sinusoid) conditions and a free viewing scanpath task. RESULTS: Individuals with schizophrenia demonstrated scanning deficits in both tasks. There was no association between performance measures of smooth pursuit and scene scanpaths in patient or control groups. Odds ratios comparing the likelihood of scanpath dysfunction when ETD was present, and the likelihood of finding scanpath dysfunction when ETD was absent were not significant in patients or controls in either pursuit variant, suggesting that ETD and scanpath dysfunction are independent anomalies in schizophrenia. CONCLUSION: ETD and scanpath disturbance appear to reflect independent oculomotor or neurocognitive deficits in schizophrenia. Each task may confer unique information about the pathophysiology of psychosis.}, keywords = {}, pubstate = {published}, tppubtype = {article} } OBJECTIVES: Smooth pursuit and visual scanpath deficits are candidate trait markers for schizophrenia. It is not clear whether eye tracking dysfunction (ETD) and atypical scanpath behaviour are the product of the same underlying neurobiological processes. We have examined co-occurrence of ETD and scanpath disturbance in individuals with schizophrenia and healthy volunteers. METHODS: Eye movements of individuals with schizophrenia (N = 96) and non-clinical age-matched comparison participants (N = 100) were recorded using non-invasive infrared oculography during smooth pursuit in both predictable (horizontal sinusoid) and less predictable (Lissajous sinusoid) conditions and a free viewing scanpath task. RESULTS: Individuals with schizophrenia demonstrated scanning deficits in both tasks. There was no association between performance measures of smooth pursuit and scene scanpaths in patient or control groups. Odds ratios comparing the likelihood of scanpath dysfunction when ETD was present, and the likelihood of finding scanpath dysfunction when ETD was absent were not significant in patients or controls in either pursuit variant, suggesting that ETD and scanpath dysfunction are independent anomalies in schizophrenia. CONCLUSION: ETD and scanpath disturbance appear to reflect independent oculomotor or neurocognitive deficits in schizophrenia. Each task may confer unique information about the pathophysiology of psychosis. |
R J van Beers The sources of variability in saccadic eye movements Journal Article Journal of Neuroscience, 27 (33), pp. 8757–8770, 2007. @article{Beers2007, title = {The sources of variability in saccadic eye movements}, author = {R J van Beers}, doi = {10.1523/JNEUROSCI.2311-07.2007}, year = {2007}, date = {2007-01-01}, journal = {Journal of Neuroscience}, volume = {27}, number = {33}, pages = {8757--8770}, abstract = {Our movements are variable, but the origin of this variability is poorly understood. We examined the sources of variability in human saccadic eye movements. In two experiments, we measured the spatiotemporal variability in saccade trajectories as a function of movement direction and amplitude. One of our new observations is that the variability in movement direction is smaller for purely horizontal and vertical saccades than for saccades in oblique directions. We also found that saccade amplitude, duration, and peak velocity are all correlated with one another. To determine the origin of the observed variability, we estimated the noise in motor commands from the observed spatiotemporal variability, while taking into account the variability resulting from uncertainty in localization of the target. This analysis revealed that uncertainty in target localization is the major source of variability in saccade endpoints, whereas noise in the magnitude of the motor commands explains a slightly smaller fraction. In addition, there is temporal variability such that saccades with a longer than average duration have a smaller than average peak velocity. This noise model has a large generality because it correctly predicts the variability in other data sets, which contain saccades starting from very different initial locations. Because the temporal noise most likely originates in movement planning, and the motor command noise in movement execution, we conclude that uncertainty in sensory signals and noise in movement planning and execution all contribute to the variability in saccade trajectories. These results are important for understanding how the brain controls movement.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Our movements are variable, but the origin of this variability is poorly understood. We examined the sources of variability in human saccadic eye movements. In two experiments, we measured the spatiotemporal variability in saccade trajectories as a function of movement direction and amplitude. One of our new observations is that the variability in movement direction is smaller for purely horizontal and vertical saccades than for saccades in oblique directions. We also found that saccade amplitude, duration, and peak velocity are all correlated with one another. To determine the origin of the observed variability, we estimated the noise in motor commands from the observed spatiotemporal variability, while taking into account the variability resulting from uncertainty in localization of the target. This analysis revealed that uncertainty in target localization is the major source of variability in saccade endpoints, whereas noise in the magnitude of the motor commands explains a slightly smaller fraction. In addition, there is temporal variability such that saccades with a longer than average duration have a smaller than average peak velocity. This noise model has a large generality because it correctly predicts the variability in other data sets, which contain saccades starting from very different initial locations. Because the temporal noise most likely originates in movement planning, and the motor command noise in movement execution, we conclude that uncertainty in sensory signals and noise in movement planning and execution all contribute to the variability in saccade trajectories. These results are important for understanding how the brain controls movement. |
Nathalie N Bélanger; Michelle Lee; Elizabeth R Schotter Young skilled deaf readers have an enhanced perceptual span in reading Journal Article Quarterly Journal of Experimental Psychology, 71 (1), pp. 291–301, 2018. @article{Belanger2018, title = {Young skilled deaf readers have an enhanced perceptual span in reading}, author = {Nathalie N Bélanger and Michelle Lee and Elizabeth R Schotter}, doi = {10.1080/17470218.2017.1324498}, year = {2018}, date = {2018-01-01}, journal = {Quarterly Journal of Experimental Psychology}, volume = {71}, number = {1}, pages = {291--301}, abstract = {Recent evidence suggests that deaf people have enhanced visual attention to simple stimuli in the parafovea in comparison to hearing people. Although a large part of reading involves processing the fixated words in foveal vision, readers also utilize information in parafoveal vision to pre-process upcoming words and decide where to look next. We investigated whether auditory deprivation affects low-level visual processing during reading, and compared the perceptual span of deaf signers who were skilled and less skilled readers to that of skilled hearing readers. Compared to hearing readers, deaf readers had a larger perceptual span than would be expected by their reading ability. These results provide the first evidence that deaf readers' enhanced attentional allocation to the parafovea is used during a complex cognitive task such as reading.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Recent evidence suggests that deaf people have enhanced visual attention to simple stimuli in the parafovea in comparison to hearing people. Although a large part of reading involves processing the fixated words in foveal vision, readers also utilize information in parafoveal vision to pre-process upcoming words and decide where to look next. We investigated whether auditory deprivation affects low-level visual processing during reading, and compared the perceptual span of deaf signers who were skilled and less skilled readers to that of skilled hearing readers. Compared to hearing readers, deaf readers had a larger perceptual span than would be expected by their reading ability. These results provide the first evidence that deaf readers' enhanced attentional allocation to the parafovea is used during a complex cognitive task such as reading. |
Christian Bellebaum; Irene Daum; B Koch; M Schwarz; K P Hoffmann The role of the human thalamus in processing corollary discharge Journal Article Brain, 128 (5), pp. 1139–1154, 2005. @article{Bellebaum2005, title = {The role of the human thalamus in processing corollary discharge}, author = {Christian Bellebaum and Irene Daum and B Koch and M Schwarz and K P Hoffmann}, doi = {10.1093/brain/awh474}, year = {2005}, date = {2005-01-01}, journal = {Brain}, volume = {128}, number = {5}, pages = {1139--1154}, abstract = {Corollary discharge signals play an important role in monitoring self-generated movements to guarantee spatial constancy. Recent work in macaques suggests that the thalamus conveys corollary discharge information of upcoming saccades passing from the superior colliculus to the frontal eye field. The present study aimed to investigate the involvement of the thalamus in humans by assessing the effect of thalamic lesions on the processing of corollary discharge information. Thirteen patients with selective thalamic lesions and 13 healthy age-matched control subjects performed a saccadic double-step task in which retino-spatial dissonance was induced, i.e. the retinal vector of the second target and the movement vector of the second saccade were different. Thus, the subjects could not rely on retinal information alone, but had to use corollary discharge information to correctly perform the second saccade. The amplitudes of first and second saccades were significantly smaller in patients than in controls. Five thalamic lesion patients showed unilateral deficits in using corollary discharge information, as revealed by asymmetries compared with the other patients and controls. Three patients with lateral thalamic lesions including the ventrolateral nucleus (VL) were impaired contralaterally to the side of damage and one patient with a lesion in the mediodorsal thalamus (MD) was impaired ipsilaterally to the lesion. The largest asymmetry was found in a patient with a bilateral thalamic lesion. The results provide evidence for a thalamic involvement in the processing of corollary discharge information in humans, with a potential role of both the VL and MD nuclei}, keywords = {}, pubstate = {published}, tppubtype = {article} } Corollary discharge signals play an important role in monitoring self-generated movements to guarantee spatial constancy. Recent work in macaques suggests that the thalamus conveys corollary discharge information of upcoming saccades passing from the superior colliculus to the frontal eye field. The present study aimed to investigate the involvement of the thalamus in humans by assessing the effect of thalamic lesions on the processing of corollary discharge information. Thirteen patients with selective thalamic lesions and 13 healthy age-matched control subjects performed a saccadic double-step task in which retino-spatial dissonance was induced, i.e. the retinal vector of the second target and the movement vector of the second saccade were different. Thus, the subjects could not rely on retinal information alone, but had to use corollary discharge information to correctly perform the second saccade. The amplitudes of first and second saccades were significantly smaller in patients than in controls. Five thalamic lesion patients showed unilateral deficits in using corollary discharge information, as revealed by asymmetries compared with the other patients and controls. Three patients with lateral thalamic lesions including the ventrolateral nucleus (VL) were impaired contralaterally to the side of damage and one patient with a lesion in the mediodorsal thalamus (MD) was impaired ipsilaterally to the lesion. The largest asymmetry was found in a patient with a bilateral thalamic lesion. The results provide evidence for a thalamic involvement in the processing of corollary discharge information in humans, with a potential role of both the VL and MD nuclei |
Christian Bellebaum; Klaus-Peter Hoffmann; Irene Daum Post-saccadic updating of visual space in the posterior parietal cortex in humans Journal Article Behavioural Brain Research, 163 (2), pp. 194–203, 2005. @article{Bellebaum2005a, title = {Post-saccadic updating of visual space in the posterior parietal cortex in humans}, author = {Christian Bellebaum and Klaus-Peter Hoffmann and Irene Daum}, doi = {10.1016/j.bbr.2005.05.007}, year = {2005}, date = {2005-01-01}, journal = {Behavioural Brain Research}, volume = {163}, number = {2}, pages = {194--203}, abstract = {Updating of visual space takes place in the posterior parietal cortex to guarantee spatial constancy across eye movements. However, the timing of updating with respect to saccadic eye movements remains a matter of debate. In the present study, event-related potentials (ERPs) were recorded in 15 volunteers during a saccadic double-step task to elucidate the time course of the updating process. In the experimental condition updating of visual space was required, because both saccade targets had already disappeared before the first saccade was executed. A similar task without updating requirements served as control condition. ERP analysis revealed a significantly larger slow positive wave in the retino-spatial dissonance condition compared to the control condition, starting between 150 and 200 ms after first saccade onset. Source analysis showed an asymmetry with respect to the direction of the first saccade. Whereas the source was restricted to the right PPC in trials with leftward first saccades, left and right PPC were involved in rightward trials. The results of the present study suggest that updating of visual space in a saccadic double-step task occurs not earlier than 150 ms after the onset of the first saccade. We conclude that extraretinal information about the first saccade is integrated with motor information about the second saccade in the inter-saccade interval.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Updating of visual space takes place in the posterior parietal cortex to guarantee spatial constancy across eye movements. However, the timing of updating with respect to saccadic eye movements remains a matter of debate. In the present study, event-related potentials (ERPs) were recorded in 15 volunteers during a saccadic double-step task to elucidate the time course of the updating process. In the experimental condition updating of visual space was required, because both saccade targets had already disappeared before the first saccade was executed. A similar task without updating requirements served as control condition. ERP analysis revealed a significantly larger slow positive wave in the retino-spatial dissonance condition compared to the control condition, starting between 150 and 200 ms after first saccade onset. Source analysis showed an asymmetry with respect to the direction of the first saccade. Whereas the source was restricted to the right PPC in trials with leftward first saccades, left and right PPC were involved in rightward trials. The results of the present study suggest that updating of visual space in a saccadic double-step task occurs not earlier than 150 ms after the onset of the first saccade. We conclude that extraretinal information about the first saccade is integrated with motor information about the second saccade in the inter-saccade interval. |
Joachim Bellet; Chih-Yang Chen; Ziad M Hafed Sequential hemifield gating of alpha and beta behavioral performance oscillations after microsaccades Journal Article Journal of Neurophysiology, 118 , pp. 2789–2805, 2017. @article{Bellet2017, title = {Sequential hemifield gating of alpha and beta behavioral performance oscillations after microsaccades}, author = {Joachim Bellet and Chih-Yang Chen and Ziad M Hafed}, doi = {10.1152/jn.00253.2017}, year = {2017}, date = {2017-01-01}, journal = {Journal of Neurophysiology}, volume = {118}, pages = {2789--2805}, abstract = {Microsaccades are tiny saccades that occur during gaze fixation. Even though visual processing has been shown to be strongly modulated close to the time of microsaccades, both at central and peripheral eccentricities, it is not clear how these eye movements might influence longer term fluctuations in brain activity and behavior. Here we found that visual processing is significantly affected and, in a rhythmic manner, even several hundreds of milliseconds after a microsaccade. Human visual detection efficiency, as measured by reaction time, exhibited coherent rhythmic oscillations in the ? - and ? -frequency bands for up to ~650–700 ms after a microsaccade. Surprisingly, the oscillations were sequentially pulsed across visual hemifields relative to microsaccade direction, first occurring in the same hemifield as the movement vector for ~400 ms and then the opposite. Such pulsing also affected perceptual detection performance. Our results suggest that visual processing is subject to long-lasting oscillations that are phase locked to microsaccade generation, and that these oscillations are dependent on microsaccade direction.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Microsaccades are tiny saccades that occur during gaze fixation. Even though visual processing has been shown to be strongly modulated close to the time of microsaccades, both at central and peripheral eccentricities, it is not clear how these eye movements might influence longer term fluctuations in brain activity and behavior. Here we found that visual processing is significantly affected and, in a rhythmic manner, even several hundreds of milliseconds after a microsaccade. Human visual detection efficiency, as measured by reaction time, exhibited coherent rhythmic oscillations in the ? - and ? -frequency bands for up to ~650–700 ms after a microsaccade. Surprisingly, the oscillations were sequentially pulsed across visual hemifields relative to microsaccade direction, first occurring in the same hemifield as the movement vector for ~400 ms and then the opposite. Such pulsing also affected perceptual detection performance. Our results suggest that visual processing is subject to long-lasting oscillations that are phase locked to microsaccade generation, and that these oscillations are dependent on microsaccade direction. |
Caren Bellmann; Mary Feely; Michael D Crossland; Stamatina A Kabanarou; Gary S Rubin Fixation stability using central and pericentral fixation targets in patients with age-related macular degeneration Journal Article Ophthalmology, 111 (12), pp. 2265–2270, 2004. @article{Bellmann2004, title = {Fixation stability using central and pericentral fixation targets in patients with age-related macular degeneration}, author = {Caren Bellmann and Mary Feely and Michael D Crossland and Stamatina A Kabanarou and Gary S Rubin}, doi = {10.1016/j.ophtha.2004.06.019}, year = {2004}, date = {2004-01-01}, journal = {Ophthalmology}, volume = {111}, number = {12}, pages = {2265--2270}, abstract = {To determine fixation stability for central and pericentral fixation targets in patients with age-related macular degeneration (AMD). Comparative study. Twelve patients having late-stage AMD involving the fovea and 10 age-matched controls having no other eye diseases and visual acuity better than 20/25. Six different fixation targets (1°cross; 1°filled circle; 1°letter x; small 4-point diamond; large 4-point diamond using dimensions as in a field analyzer; large-crossover whole-image diagonal with open 1°center) were presented on a high-resolution monitor. Before examination, subjects were given verbal instructions to move their eye to see the center of the target best. Fixation stability was measured for the preferred eye, with the fellow eye occluded, using a gaze tracker. Fixation stability was quantified by calculating the bivariate contour ellipse area (BCEA) over 30 seconds for each target. For statistical analysis, BCEA values (minutes of arc2) were converted into their logarithms. The absolute retinal scotoma for the study eye was determined using a scanning laser ophthalmoscope. Bivariate contour ellipse area. Visual acuity in patients (age range, 57-87 years) ranged from 20/32 to 20/600. The lowest BCEA values were found for the 1°letter x in patients (mean, 12052.2%±254.0%) and for the 1°cross in normal subjects (mean, 1286.9%±47.8%); the highest BCEA values were found for the small 4-point diamond in patients (mean, 23109.5%±298.3%) and for the large 4-point diamond in normals (age range, 62-79 years) (mean, 3229.2%±105.4%). The difference between the targets was significant for normal subjects (analysis of variance [ANOVA], Ptextless0.01) but not for patients (ANOVA, Ptextgreater0.05). In normals, BCEA values were significantly lower for central fixation targets than for pericentral fixation targets (Ptextless0.01). Fixation is significantly less stable for pericentral fixation targets in normal subjects, indicating an advantage for central fixation targets. These results are particularly significant for any clinical and experimental testing method that requires the patient to maintain stable fixation.}, keywords = {}, pubstate = {published}, tppubtype = {article} } To determine fixation stability for central and pericentral fixation targets in patients with age-related macular degeneration (AMD). Comparative study. Twelve patients having late-stage AMD involving the fovea and 10 age-matched controls having no other eye diseases and visual acuity better than 20/25. Six different fixation targets (1°cross; 1°filled circle; 1°letter x; small 4-point diamond; large 4-point diamond using dimensions as in a field analyzer; large-crossover whole-image diagonal with open 1°center) were presented on a high-resolution monitor. Before examination, subjects were given verbal instructions to move their eye to see the center of the target best. Fixation stability was measured for the preferred eye, with the fellow eye occluded, using a gaze tracker. Fixation stability was quantified by calculating the bivariate contour ellipse area (BCEA) over 30 seconds for each target. For statistical analysis, BCEA values (minutes of arc2) were converted into their logarithms. The absolute retinal scotoma for the study eye was determined using a scanning laser ophthalmoscope. Bivariate contour ellipse area. Visual acuity in patients (age range, 57-87 years) ranged from 20/32 to 20/600. The lowest BCEA values were found for the 1°letter x in patients (mean, 12052.2%±254.0%) and for the 1°cross in normal subjects (mean, 1286.9%±47.8%); the highest BCEA values were found for the small 4-point diamond in patients (mean, 23109.5%±298.3%) and for the large 4-point diamond in normals (age range, 62-79 years) (mean, 3229.2%±105.4%). The difference between the targets was significant for normal subjects (analysis of variance [ANOVA], Ptextless0.01) but not for patients (ANOVA, Ptextgreater0.05). In normals, BCEA values were significantly lower for central fixation targets than for pericentral fixation targets (Ptextless0.01). Fixation is significantly less stable for pericentral fixation targets in normal subjects, indicating an advantage for central fixation targets. These results are particularly significant for any clinical and experimental testing method that requires the patient to maintain stable fixation. |
Artem V Belopolsky; Jan Theeuwes Selection within visual memory representations activates the oculomotor system Journal Article Neuropsychologia, 49 (6), pp. 1605–1610, 2011. @article{Belopolsky2011a, title = {Selection within visual memory representations activates the oculomotor system}, author = {Artem V Belopolsky and Jan Theeuwes}, doi = {10.1016/j.neuropsychologia.2010.12.045}, year = {2011}, date = {2011-01-01}, journal = {Neuropsychologia}, volume = {49}, number = {6}, pages = {1605--1610}, publisher = {Elsevier Ltd}, abstract = {Humans tend to create and maintain internal representations of the environment that help guiding actions during the everyday activities. Previous studies have shown that the oculomotor system is involved in coding and maintenance of locations in visual-spatial working memory. In these studies selection of the relevant location for maintenance in working memory took place on the screen (selecting the location of a dot presented on the screen). The present study extended these findings by showing that the oculomotor system also codes selection of location from an internal memory representation. Participants first memorized two locations and after a retention interval selected one location for further maintenance. The results show that saccade trajectories deviated away from the ultimately remembered location. Furthermore, selection of the location from the memorized representation produced sustained oculomotor preparation to it. The results show that oculomotor system is very flexible and plays an active role for coding and maintaining information selected within internal memory representations.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Humans tend to create and maintain internal representations of the environment that help guiding actions during the everyday activities. Previous studies have shown that the oculomotor system is involved in coding and maintenance of locations in visual-spatial working memory. In these studies selection of the relevant location for maintenance in working memory took place on the screen (selecting the location of a dot presented on the screen). The present study extended these findings by showing that the oculomotor system also codes selection of location from an internal memory representation. Participants first memorized two locations and after a retention interval selected one location for further maintenance. The results show that saccade trajectories deviated away from the ultimately remembered location. Furthermore, selection of the location from the memorized representation produced sustained oculomotor preparation to it. The results show that oculomotor system is very flexible and plays an active role for coding and maintaining information selected within internal memory representations. |
Artem V Belopolsky; Jan Theeuwes Updating the premotor theory: The allocation of attention is not always accompanied by saccade preparation Journal Article Journal of Experimental Psychology: Human Perception and Performance, 38 (4), pp. 902–914, 2012. @article{Belopolsky2012, title = {Updating the premotor theory: The allocation of attention is not always accompanied by saccade preparation}, author = {Artem V Belopolsky and Jan Theeuwes}, doi = {10.1037/a0028662}, year = {2012}, date = {2012-01-01}, journal = {Journal of Experimental Psychology: Human Perception and Performance}, volume = {38}, number = {4}, pages = {902--914}, abstract = {There is an ongoing controversy regarding the relationship between covert attention and saccadic eye movements. While there is quite some evidence that the preparation of a saccade is obligatory preceded by a shift of covert attention, the reverse is not clear: Is allocation of attention always accompanied by saccade preparation? Recently, a shifting and maintenance account was proposed suggesting that shifting and maintenance components of covert attention differ in their relation to the oculomotor system. Specifically, it was argued that a shift of covert attention is always accompanied by activation of the oculomotor program, while maintaining covert attention at a location can be accompanied either by activation or suppression of oculomotor program, depending on the probability of executing an eye movement to the attended location. In the present study we tested whether there is such an obligatory coupling between shifting of attention and saccade preparation and how quickly saccade preparation gets suppressed. The results showed that attention shifting was always accompanied by saccade preparation whenever covert attention had to be shifted during visual search, as well as in response to exogenous or endogenous cues. However, for the endogenous cues the saccade program to the attended location was suppressed very soon after the attention shift was completed. The current findings support the shifting and maintenance account and indicate that the premotor theory needs to be updated to include a shifting and maintenance component for the cases in which covert shifts of attention are made without the intention to execute a saccade.}, keywords = {}, pubstate = {published}, tppubtype = {article} } There is an ongoing controversy regarding the relationship between covert attention and saccadic eye movements. While there is quite some evidence that the preparation of a saccade is obligatory preceded by a shift of covert attention, the reverse is not clear: Is allocation of attention always accompanied by saccade preparation? Recently, a shifting and maintenance account was proposed suggesting that shifting and maintenance components of covert attention differ in their relation to the oculomotor system. Specifically, it was argued that a shift of covert attention is always accompanied by activation of the oculomotor program, while maintaining covert attention at a location can be accompanied either by activation or suppression of oculomotor program, depending on the probability of executing an eye movement to the attended location. In the present study we tested whether there is such an obligatory coupling between shifting of attention and saccade preparation and how quickly saccade preparation gets suppressed. The results showed that attention shifting was always accompanied by saccade preparation whenever covert attention had to be shifted during visual search, as well as in response to exogenous or endogenous cues. However, for the endogenous cues the saccade program to the attended location was suppressed very soon after the attention shift was completed. The current findings support the shifting and maintenance account and indicate that the premotor theory needs to be updated to include a shifting and maintenance component for the cases in which covert shifts of attention are made without the intention to execute a saccade. |
A V Belopolsky; S Van der Stigchel Saccades curve away from previously inhibited locations: Evidence for the role of priming in oculomotor competition Journal Article Journal of Neurophysiology, 110 (10), pp. 2370–2377, 2013. @article{Belopolsky2013, title = {Saccades curve away from previously inhibited locations: Evidence for the role of priming in oculomotor competition}, author = {A V Belopolsky and S {Van der Stigchel}}, doi = {10.1152/jn.00293.2013}, year = {2013}, date = {2013-01-01}, journal = {Journal of Neurophysiology}, volume = {110}, number = {10}, pages = {2370--2377}, abstract = {The oculomotor system serves as the basis for representing concurrently competing motor programs. Here, we examine whether the oculomotor system also keeps track of the outcome of competition between target and distractor on the previous trial. Participants had to perform a simple task of making a saccade toward a predefined direction. On two-thirds of the trials, an irrelevant distractor was presented to either the left or right of the fixation. On one-third of the trials, no distractor was present. The results show that on trials without a distractor, saccades curved away from the empty location that was occupied by a distractor on the previous trial. This result was replicated and extended to cases when different saccade directions were used. In addition, we show that repetition of distractor location on the distractor-present trials results in a stronger curvature away and in a shorter saccade latency to the target. Taken together, these results provide strong evidence that the oculomotor system automatically codes and retains locations that had been ignored in the past to bias future behavior.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The oculomotor system serves as the basis for representing concurrently competing motor programs. Here, we examine whether the oculomotor system also keeps track of the outcome of competition between target and distractor on the previous trial. Participants had to perform a simple task of making a saccade toward a predefined direction. On two-thirds of the trials, an irrelevant distractor was presented to either the left or right of the fixation. On one-third of the trials, no distractor was present. The results show that on trials without a distractor, saccades curved away from the empty location that was occupied by a distractor on the previous trial. This result was replicated and extended to cases when different saccade directions were used. In addition, we show that repetition of distractor location on the distractor-present trials results in a stronger curvature away and in a shorter saccade latency to the target. Taken together, these results provide strong evidence that the oculomotor system automatically codes and retains locations that had been ignored in the past to bias future behavior. |
Alessandro Benedetto; Paola Binda Dissociable saccadic suppression of pupillary and perceptual responses to light Journal Article Journal of Neurophysiology, 115 (3), pp. 1243–1251, 2016. @article{Benedetto2016, title = {Dissociable saccadic suppression of pupillary and perceptual responses to light}, author = {Alessandro Benedetto and Paola Binda}, doi = {10.1152/jn.00964.2015}, year = {2016}, date = {2016-01-01}, journal = {Journal of Neurophysiology}, volume = {115}, number = {3}, pages = {1243--1251}, abstract = {We measured pupillary constrictions in response to full-screen flashes of variable luminance, occurring either at the onset of a saccadic eye movement or well before/after it. A large fraction of perisaccadic flashes were undetectable to the subjects, consistent with saccadic suppression of visual sensitivity. Likewise, pupillary responses to perisaccadic flashes were strongly suppressed. However, the two phenomena appear to be dissociable. Across subjects and luminance levels of the flash stimulus, there were cases in which conscious perception of the flash was completely depleted yet the pupillary response was clearly present, as well as cases in which the opposite occurred. On one hand, the fact that pupillary light responses are subject to saccadic suppression reinforces evidence that this is not a simple reflex but depends on the integration of retinal illumination with complex "extraretinal" cues. On the other hand, the relative independence of pupillary and perceptual responses suggests that suppression acts separately on these systems-consistent with the idea of multiple visual pathways that are differentially affected by saccades.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We measured pupillary constrictions in response to full-screen flashes of variable luminance, occurring either at the onset of a saccadic eye movement or well before/after it. A large fraction of perisaccadic flashes were undetectable to the subjects, consistent with saccadic suppression of visual sensitivity. Likewise, pupillary responses to perisaccadic flashes were strongly suppressed. However, the two phenomena appear to be dissociable. Across subjects and luminance levels of the flash stimulus, there were cases in which conscious perception of the flash was completely depleted yet the pupillary response was clearly present, as well as cases in which the opposite occurred. On one hand, the fact that pupillary light responses are subject to saccadic suppression reinforces evidence that this is not a simple reflex but depends on the integration of retinal illumination with complex "extraretinal" cues. On the other hand, the relative independence of pupillary and perceptual responses suggests that suppression acts separately on these systems-consistent with the idea of multiple visual pathways that are differentially affected by saccades. |
Alessandro Benedetto; Maria Concetta Morrone Saccadic suppression is embedded within extended oscillatory modulation of sensitivity Journal Article Journal of Neuroscience, 37 (13), pp. 3661–3670, 2017. @article{Benedetto2017, title = {Saccadic suppression is embedded within extended oscillatory modulation of sensitivity}, author = {Alessandro Benedetto and Maria Concetta Morrone}, doi = {10.1523/JNEUROSCI.2390-16.2016}, year = {2017}, date = {2017-01-01}, journal = {Journal of Neuroscience}, volume = {37}, number = {13}, pages = {3661--3670}, abstract = {Action and perception are intimately coupled systems. One clear case is saccadic suppression, the reduced visibility around the time of saccades, which is important in mediating visual stability; another is the oscillatory modulation of visibility synchronized with hand action. To suppress effectively the spurious retinal motion generated by the eye movements, it is crucial that saccadic suppression and saccadic onset be temporally synchronous. However, the mechanisms that determine this temporal synchrony are unknown. We investigated the effect of saccades on contrast discrimination sensitivity over a long period stretching over textgreater1 s before and after saccade execution. Human subjects made horizontal saccades at will to two stationary saccadic targets separated by 20°. At a random interval, a brief Gabor patch was displayed between the two fixations in either the upper or lower visual field and the subject had to detect its location. Strong saccadic suppression was measured between -50 and 50 ms from saccadic onset. However, the suppression was systematically embedded in a trough of oscillations of contrast sensitivity that fluctuated rhythmically in the delta range (at ∼3 Hz), commencing ∼1 s before saccade execution and lasting for up to 1 s after the saccade. The results show that saccadic preparation and visual sensitivity oscillations are coupled and the coupling might be instrumental in temporally aligning the initiation of the saccade with the visual suppression.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Action and perception are intimately coupled systems. One clear case is saccadic suppression, the reduced visibility around the time of saccades, which is important in mediating visual stability; another is the oscillatory modulation of visibility synchronized with hand action. To suppress effectively the spurious retinal motion generated by the eye movements, it is crucial that saccadic suppression and saccadic onset be temporally synchronous. However, the mechanisms that determine this temporal synchrony are unknown. We investigated the effect of saccades on contrast discrimination sensitivity over a long period stretching over textgreater1 s before and after saccade execution. Human subjects made horizontal saccades at will to two stationary saccadic targets separated by 20°. At a random interval, a brief Gabor patch was displayed between the two fixations in either the upper or lower visual field and the subject had to detect its location. Strong saccadic suppression was measured between -50 and 50 ms from saccadic onset. However, the suppression was systematically embedded in a trough of oscillations of contrast sensitivity that fluctuated rhythmically in the delta range (at ∼3 Hz), commencing ∼1 s before saccade execution and lasting for up to 1 s after the saccade. The results show that saccadic preparation and visual sensitivity oscillations are coupled and the coupling might be instrumental in temporally aligning the initiation of the saccade with the visual suppression. |
Brittany Benjamin; Christopher Macomb; Alisha Martin; Aaron L Cecala Preliminary Report: Can color act as a contextual cue in human saccadic adaptation? Journal Article Bios, 87 (1), pp. 9–20, 2016. @article{Benjamin2016, title = {Preliminary Report: Can color act as a contextual cue in human saccadic adaptation?}, author = {Brittany Benjamin and Christopher Macomb and Alisha Martin and Aaron L Cecala}, doi = {http://dx.doi.org/10.1893/BIOS-D-14-00011.1}, year = {2016}, date = {2016-01-01}, journal = {Bios}, volume = {87}, number = {1}, pages = {9--20}, abstract = {When the head does not move, rapid movements of the eyes called saccades are used to redirect the line of sight. Saccades are defined by a series of metrical and kinematic (evolution of a movement as a function of time) relationships. For example, the amplitude of a saccade made from one visual target to another is roughly 90% of the distance between the initial fixation point (T0) and the peripheral target (T1). However, this stereotypical relationship between saccade amplitude and initial retinal error (jT1-Initial Eye Positionj) may be altered, either increased or decreased, by surreptitiously displacing a visual target during an ongoing saccade. This form of saccadic adaptation has been described in both humans and monkeys. We investigated the effects of a contextual cue (target color) on the magnitude of human saccadic adaptation using an eye tracker to measure our subjects' eye position. Our results indicate that target color cannot be used by the eye movement control system to elicit differential changes in motor output regardless of whether the color cues are randomly intermixed or presented sequentially.}, keywords = {}, pubstate = {published}, tppubtype = {article} } When the head does not move, rapid movements of the eyes called saccades are used to redirect the line of sight. Saccades are defined by a series of metrical and kinematic (evolution of a movement as a function of time) relationships. For example, the amplitude of a saccade made from one visual target to another is roughly 90% of the distance between the initial fixation point (T0) and the peripheral target (T1). However, this stereotypical relationship between saccade amplitude and initial retinal error (jT1-Initial Eye Positionj) may be altered, either increased or decreased, by surreptitiously displacing a visual target during an ongoing saccade. This form of saccadic adaptation has been described in both humans and monkeys. We investigated the effects of a contextual cue (target color) on the magnitude of human saccadic adaptation using an eye tracker to measure our subjects' eye position. Our results indicate that target color cannot be used by the eye movement control system to elicit differential changes in motor output regardless of whether the color cues are randomly intermixed or presented sequentially. |
Philip J Benson; Ute Leonards; Robert M Lothian; David M St. Clair; Marco C G Merlo Visual scan paths in first-episode schizophrenia and cannabis-induced psychosis Journal Article Journal of Psychiatry and Neuroscience, 32 (4), pp. 267–274, 2007. @article{Benson2007, title = {Visual scan paths in first-episode schizophrenia and cannabis-induced psychosis}, author = {Philip J Benson and Ute Leonards and Robert M Lothian and David M {St. Clair} and Marco C G Merlo}, doi = {10.1111/bjd.13740}, year = {2007}, date = {2007-01-01}, journal = {Journal of Psychiatry and Neuroscience}, volume = {32}, number = {4}, pages = {267--274}, abstract = {OBJECTIVE: Patterns of successive saccades and fixations (scan paths) that are made while viewing images are often spatially restricted in schizophrenia, but the relation with cannabis-induced psychosis has not been examined. We used higher-order statistical methods to examine spatiotemporal characteristics of scan paths to determine whether viewing behaviour was distinguishable on a continuum. METHODS: Patients with early acute first-episode paranoid schizophrenia (SCH; n = 11), cannabis-induced psychosis (CIP; n = 6) and unaffected control subjects (n = 22) undertook a task requiring free viewing of facial, fractal and landscape images for 5 seconds while their eye movements were recorded. Frequencies and distributions of saccades and fixations were calculated in relation to image regions examined during each trial. RESULTS: Findings were independent of image category, indicating generalized scanning deficits. Compared with control subjects, patients with SCH and CIP made fewer saccades and fewer fixations of longer duration. In turn, the spatial distribution of fixations in CIP patients was more clustered than in SCH and control subjects. The diversity of features fixated in subjects with CIP was also lower than in SCH patients and control subjects. CONCLUSION: A continuous approach to characterizing scan path changes in different phenotypes suggests that CIP shares some of the abnormalities of SCH but can be distinguished with measures that are sensitive to cognitive strategies active or inhibited during visual exploration.}, keywords = {}, pubstate = {published}, tppubtype = {article} } OBJECTIVE: Patterns of successive saccades and fixations (scan paths) that are made while viewing images are often spatially restricted in schizophrenia, but the relation with cannabis-induced psychosis has not been examined. We used higher-order statistical methods to examine spatiotemporal characteristics of scan paths to determine whether viewing behaviour was distinguishable on a continuum. METHODS: Patients with early acute first-episode paranoid schizophrenia (SCH; n = 11), cannabis-induced psychosis (CIP; n = 6) and unaffected control subjects (n = 22) undertook a task requiring free viewing of facial, fractal and landscape images for 5 seconds while their eye movements were recorded. Frequencies and distributions of saccades and fixations were calculated in relation to image regions examined during each trial. RESULTS: Findings were independent of image category, indicating generalized scanning deficits. Compared with control subjects, patients with SCH and CIP made fewer saccades and fewer fixations of longer duration. In turn, the spatial distribution of fixations in CIP patients was more clustered than in SCH and control subjects. The diversity of features fixated in subjects with CIP was also lower than in SCH patients and control subjects. CONCLUSION: A continuous approach to characterizing scan path changes in different phenotypes suggests that CIP shares some of the abnormalities of SCH but can be distinguished with measures that are sensitive to cognitive strategies active or inhibited during visual exploration. |
Philip J Benson; Sara A Beedie; Elizabeth Shephard; Ina Giegling; Dan Rujescu; David St. Clair Simple viewing tests can detect eye movement abnormalities that distinguish schizophrenia cases from controls with exceptional accuracy Journal Article Biological Psychiatry, 72 (9), pp. 716–724, 2012. @article{Benson2012, title = {Simple viewing tests can detect eye movement abnormalities that distinguish schizophrenia cases from controls with exceptional accuracy}, author = {Philip J Benson and Sara A Beedie and Elizabeth Shephard and Ina Giegling and Dan Rujescu and David {St. Clair}}, doi = {10.1016/j.biopsych.2012.04.019}, year = {2012}, date = {2012-01-01}, journal = {Biological Psychiatry}, volume = {72}, number = {9}, pages = {716--724}, publisher = {Elsevier Inc.}, abstract = {Background: We have investigated which eye-movement tests alone and combined can best discriminate schizophrenia cases from control subjects and their predictive validity. Methods: A training set of 88 schizophrenia cases and 88 controls had a range of eye movements recorded; the predictive validity of the tests was then examined on eye-movement data from 34 9-month retest cases and controls, and from 36 novel schizophrenia cases and 52 control subjects. Eye movements were recorded during smooth pursuit, fixation stability, and free-viewing tasks. Group differences on performance measures were examined by univariate and multivariate analyses. Model fitting was used to compare regression, boosted tree, and probabilistic neural network approaches. Results: As a group, schizophrenia cases differed from control subjects on almost all eye-movement tests, including horizontal and Lissajous pursuit, visual scanpath, and fixation stability; fixation dispersal during free viewing was the best single discriminator. Effects were stable over time, and independent of sex, medication, or cigarette smoking. A boosted tree model achieved perfect separation of the 88 training cases from 88 control subjects; its predictive validity on retest assessments and novel cases and control subjects was 87.8%. However, when we examined the whole data set of 298 assessments, a cross-validated probabilistic neural network model was superior and could discriminate all cases from controls with near perfect accuracy at 98.3%. Conclusions: Simple viewing patterns can detect eye-movement abnormalities that can discriminate schizophrenia cases from control subjects with exceptional accuracy. textcopyright 2012 Society of Biological Psychiatry.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Background: We have investigated which eye-movement tests alone and combined can best discriminate schizophrenia cases from control subjects and their predictive validity. Methods: A training set of 88 schizophrenia cases and 88 controls had a range of eye movements recorded; the predictive validity of the tests was then examined on eye-movement data from 34 9-month retest cases and controls, and from 36 novel schizophrenia cases and 52 control subjects. Eye movements were recorded during smooth pursuit, fixation stability, and free-viewing tasks. Group differences on performance measures were examined by univariate and multivariate analyses. Model fitting was used to compare regression, boosted tree, and probabilistic neural network approaches. Results: As a group, schizophrenia cases differed from control subjects on almost all eye-movement tests, including horizontal and Lissajous pursuit, visual scanpath, and fixation stability; fixation dispersal during free viewing was the best single discriminator. Effects were stable over time, and independent of sex, medication, or cigarette smoking. A boosted tree model achieved perfect separation of the 88 training cases from 88 control subjects; its predictive validity on retest assessments and novel cases and control subjects was 87.8%. However, when we examined the whole data set of 298 assessments, a cross-validated probabilistic neural network model was superior and could discriminate all cases from controls with near perfect accuracy at 98.3%. Conclusions: Simple viewing patterns can detect eye-movement abnormalities that can discriminate schizophrenia cases from control subjects with exceptional accuracy. textcopyright 2012 Society of Biological Psychiatry. |
Valerie Benson; Monica S Castelhano; Sheena K Au-Yeung; Keith Rayner Eye movements reveal no immediate"WOW" ("which one's weird") effect in autism spectrum disorder Journal Article The Quarterly Journal of Experimental Psychology, 65 (6), pp. 1139–1150, 2012. @article{Benson2012a, title = {Eye movements reveal no immediate"WOW" ("which one's weird") effect in autism spectrum disorder}, author = {Valerie Benson and Monica S Castelhano and Sheena K Au-Yeung and Keith Rayner}, doi = {10.1080/17470218.2011.644305}, year = {2012}, date = {2012-01-01}, journal = {The Quarterly Journal of Experimental Psychology}, volume = {65}, number = {6}, pages = {1139--1150}, abstract = {Autism spectrum disorder (ASD) and typically developed (TD) adult participants viewed pairs of scenes for a simple " spot the difference " (STD) and a complex " which one's weird " (WOW) task. There were no group differences in the STD task. In the WOW task, the ASD group took longer to respond manually and to begin fixating the target " weird " region. Additionally, as indexed by the first-fixation duration into the target region, the ASD group failed to " pick up " immediately on what was " weird " . The findings are discussed with reference to the complex information processing theory of ASD (Minshew & Goldstein, 1998).}, keywords = {}, pubstate = {published}, tppubtype = {article} } Autism spectrum disorder (ASD) and typically developed (TD) adult participants viewed pairs of scenes for a simple " spot the difference " (STD) and a complex " which one's weird " (WOW) task. There were no group differences in the STD task. In the WOW task, the ASD group took longer to respond manually and to begin fixating the target " weird " region. Additionally, as indexed by the first-fixation duration into the target region, the ASD group failed to " pick up " immediately on what was " weird " . The findings are discussed with reference to the complex information processing theory of ASD (Minshew & Goldstein, 1998). |
Valerie Benson; Magdalena Ietswaart; David Milner Eye movements and verbal report in a single case of visual neglect Journal Article PLoS ONE, 7 (8), pp. 1–11, 2012. @article{Benson2012b, title = {Eye movements and verbal report in a single case of visual neglect}, author = {Valerie Benson and Magdalena Ietswaart and David Milner}, doi = {10.1371/journal.pone.0043743}, year = {2012}, date = {2012-01-01}, journal = {PLoS ONE}, volume = {7}, number = {8}, pages = {1--11}, abstract = {In this single case study, visuospatial neglect patient P1 demonstrated a dissociation between an intact ability to make appropriate reflexive eye movements to targets in the neglected field with latencies of textless400 ms, while failing to report targets presented at such durations in a separate verbal detection task. In contrast, there was a failure to evoke the usually robust Remote Distractor Effect in P1, even though distractors in the neglected field were presented at above threshold durations. Together those data indicate that the tight coupling that is normally shown between attention and eye movements appears to be disrupted for low-level orienting in P1. A comparable disruption was also found for high-level cognitive processing tasks, namely reading and scene scanning. The findings are discussed in relation to sampling, attention and awareness in neglect.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this single case study, visuospatial neglect patient P1 demonstrated a dissociation between an intact ability to make appropriate reflexive eye movements to targets in the neglected field with latencies of textless400 ms, while failing to report targets presented at such durations in a separate verbal detection task. In contrast, there was a failure to evoke the usually robust Remote Distractor Effect in P1, even though distractors in the neglected field were presented at above threshold durations. Together those data indicate that the tight coupling that is normally shown between attention and eye movements appears to be disrupted for low-level orienting in P1. A comparable disruption was also found for high-level cognitive processing tasks, namely reading and scene scanning. The findings are discussed in relation to sampling, attention and awareness in neglect. |
Valerie Benson; Monica S Castelhano; Philippa L Howard; Nida Latif; Keith Rayner Looking, seeing and believing in autism: Eye movements reveal how subtle cognitive processing differences impact in the social domain Journal Article Autism Research, 9 (8), pp. 879–887, 2016. @article{Benson2016, title = {Looking, seeing and believing in autism: Eye movements reveal how subtle cognitive processing differences impact in the social domain}, author = {Valerie Benson and Monica S Castelhano and Philippa L Howard and Nida Latif and Keith Rayner}, doi = {10.1002/aur.1580}, year = {2016}, date = {2016-01-01}, journal = {Autism Research}, volume = {9}, number = {8}, pages = {879--887}, abstract = {Adults with High Functioning Autism Spectrum Disorders (ASD) viewed scenes with people in them, while having their eye movements recorded. The task was to indicate, using a button press, whether the pictures were normal, or in some way weird or odd. Oddities in the pictures were categorized as violations of either perceptual or social norms. Compared to a Typically Developed (TD) control group, the ASD participants were equally able to categorize the scenes as odd or normal, but they took longer to respond. The eye movement patterns showed that the ASD group made more fixations and revisits to the target areas in the odd scenes compared with the TD group. Additionally, when the ASD group first fixated the target areas in the scenes, they failed to initially detect the social oddities. These two findings have clear implications for processing difficulties in ASD for the social domain, where it is important to detect social cues on-line, and where there is little opportunity to go back and recheck possible cues in fast dynamic interactions.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Adults with High Functioning Autism Spectrum Disorders (ASD) viewed scenes with people in them, while having their eye movements recorded. The task was to indicate, using a button press, whether the pictures were normal, or in some way weird or odd. Oddities in the pictures were categorized as violations of either perceptual or social norms. Compared to a Typically Developed (TD) control group, the ASD participants were equally able to categorize the scenes as odd or normal, but they took longer to respond. The eye movement patterns showed that the ASD group made more fixations and revisits to the target areas in the odd scenes compared with the TD group. Additionally, when the ASD group first fixated the target areas in the scenes, they failed to initially detect the social oddities. These two findings have clear implications for processing difficulties in ASD for the social domain, where it is important to detect social cues on-line, and where there is little opportunity to go back and recheck possible cues in fast dynamic interactions. |
Douwe P Bergsma; G Van Der Wildt Visual training of cerebral blindness patients gradually enlarges the visual field Journal Article British Journal of Ophthalmology, 94 (1), pp. 88–96, 2010. @article{Bergsma2010, title = {Visual training of cerebral blindness patients gradually enlarges the visual field}, author = {Douwe P Bergsma and G {Van Der Wildt}}, doi = {10.1136/bjo.2008.154336}, year = {2010}, date = {2010-01-01}, journal = {British Journal of Ophthalmology}, volume = {94}, number = {1}, pages = {88--96}, abstract = {BACKGROUND: Multiple studies on recovery of hemianopsia after cerebrovascular accident report visual-field enlargements after stimulation of the visual-field border area. These enlargements are made evident by the difference between pre- and post-training measurements of the visual field. Until now, it was not known how the visual-field enlargement develops. AIM: To study how the enlargement develops as a function of time. METHODS: 11 subjects were trained by stimulating the border area of their visual-field defect using a Goldmann perimeter. The visual-field border location was assessed using dynamic Goldmann perimetry before, after and during training (after each 10th training session). To monitor eye fixation, a video-based eye-tracker was used during each complete perimetry session. RESULTS: It was found that visual-field enlargement during training is actually a gradual shift of the visual-field border, which was independent of the type of stimulus-set used during training. The shift could be observed while eye fixation was accurate. CONCLUSION: Visual-detection training leads to a decrease in detection thresholds in the affected visual-field areas and to visual-field enlargement. Training effects can be generalised to important daily-life activities like reading.}, keywords = {}, pubstate = {published}, tppubtype = {article} } BACKGROUND: Multiple studies on recovery of hemianopsia after cerebrovascular accident report visual-field enlargements after stimulation of the visual-field border area. These enlargements are made evident by the difference between pre- and post-training measurements of the visual field. Until now, it was not known how the visual-field enlargement develops. AIM: To study how the enlargement develops as a function of time. METHODS: 11 subjects were trained by stimulating the border area of their visual-field defect using a Goldmann perimeter. The visual-field border location was assessed using dynamic Goldmann perimetry before, after and during training (after each 10th training session). To monitor eye fixation, a video-based eye-tracker was used during each complete perimetry session. RESULTS: It was found that visual-field enlargement during training is actually a gradual shift of the visual-field border, which was independent of the type of stimulus-set used during training. The shift could be observed while eye fixation was accurate. CONCLUSION: Visual-detection training leads to a decrease in detection thresholds in the affected visual-field areas and to visual-field enlargement. Training effects can be generalised to important daily-life activities like reading. |
Douwe P Bergsma; J A Elshout; G J van der Wildt; A V van den Berg Transfer effects of training-induced visual field recovery in patients with chronic stroke Miscellaneous 2012. @misc{Bergsma2012, title = {Transfer effects of training-induced visual field recovery in patients with chronic stroke}, author = {Douwe P Bergsma and J A Elshout and G J van der Wildt and A V van den Berg}, doi = {10.1310/tsr1903-212}, year = {2012}, date = {2012-01-01}, booktitle = {Topics in Stroke Rehabilitation}, volume = {19}, number = {3}, pages = {212--225}, abstract = {OBJECTIVE: Visual training of light detection in the transition zone between blind and healthy hemianopic visual fields leads to improvement of color and simple pattern recognition. Recently, we demonstrated that visual field enlargement (VFE) also occurs when an area just beyond the transition zone is stimulated. In the current study, we attempted to determine whether this peripheral training also causes improvement in color and shape perception and reading speed. Further, we evaluated which measure of VFE relates best to improvements in performance: the average border shift (ABS) in degrees or the estimated amount of cortical surface gain (ECSG) in millimeters, using the cortical magnification factor (CMF).$backslash$n$backslash$nMETHOD: Twelve patients received 40 sessions of 1-hour restorative function training (RFT). Before and after training, we measured visual fields and reading speed. Additionally, color and shape perception in the trained visual field area was measured in 7 patients.$backslash$n$backslash$nRESULTS: VFE was found for 9 of 12 patients. Significant improvements were observed in reading speed for 8 of 12 patients and in color and shape perception for 3 of 7 patients. ECSG correlates significantly with performance; ABS does not. Our data indicate that the threshold ECSG, needed for significant changes in color and shape perception and reading speed, is about 6 mm.$backslash$n$backslash$nCONCLUSIONS: White stimulus training-induced VFE can lead to improved color and shape perception and to increased reading speed in and beyond the pretraining transition zone if ECSG is sufficiently large. The latter depends on the eccentricity of the VFE.}, keywords = {}, pubstate = {published}, tppubtype = {misc} } OBJECTIVE: Visual training of light detection in the transition zone between blind and healthy hemianopic visual fields leads to improvement of color and simple pattern recognition. Recently, we demonstrated that visual field enlargement (VFE) also occurs when an area just beyond the transition zone is stimulated. In the current study, we attempted to determine whether this peripheral training also causes improvement in color and shape perception and reading speed. Further, we evaluated which measure of VFE relates best to improvements in performance: the average border shift (ABS) in degrees or the estimated amount of cortical surface gain (ECSG) in millimeters, using the cortical magnification factor (CMF).$backslash$n$backslash$nMETHOD: Twelve patients received 40 sessions of 1-hour restorative function training (RFT). Before and after training, we measured visual fields and reading speed. Additionally, color and shape perception in the trained visual field area was measured in 7 patients.$backslash$n$backslash$nRESULTS: VFE was found for 9 of 12 patients. Significant improvements were observed in reading speed for 8 of 12 patients and in color and shape perception for 3 of 7 patients. ECSG correlates significantly with performance; ABS does not. Our data indicate that the threshold ECSG, needed for significant changes in color and shape perception and reading speed, is about 6 mm.$backslash$n$backslash$nCONCLUSIONS: White stimulus training-induced VFE can lead to improved color and shape perception and to increased reading speed in and beyond the pretraining transition zone if ECSG is sufficiently large. The latter depends on the eccentricity of the VFE. |
Douwe P Bergsma; Joris A Elshout; Albert V van den Berg Segregation of spontaneous and training induced recovery from visual field defects in subacute stroke patients Journal Article Frontiers in Neurology, 8 , pp. 1–12, 2017. @article{Bergsma2017, title = {Segregation of spontaneous and training induced recovery from visual field defects in subacute stroke patients}, author = {Douwe P Bergsma and Joris A Elshout and Albert V van den Berg}, doi = {10.3389/fneur.2017.00681}, year = {2017}, date = {2017-01-01}, journal = {Frontiers in Neurology}, volume = {8}, pages = {1--12}, abstract = {Whether rehabilitation after stroke profits from an early start is difficult to establish as the contributions of spontaneous recovery and treatment are difficult to tease apart. Here, we use a novel training design to dissociate these components for visual rehabilitation of subacute stroke patients with visual field defects such as hemianopia. Visual discrimination training was started within 6 weeks after stroke in 17 patients. Spontaneous and training-induced recoveries were distinguished by training one-half of the defect for 8 weeks, while monitoring spontaneous recovery in the other (control) half of the defect. Next, trained and control regions were swapped, and training continued for another 8 weeks. The same paradigm was also applied to seven chronic patients for whom spontaneous recovery can be excluded and changes in the control half of the defect point to a spillover effect of training. In both groups, field stability was assessed during a no-intervention period. Defect reduction was significantly greater in the trained part of the defect than in the simultaneously untrained part of the defect irrespective of training onset (p = 0.001). In subacute patients, training contributed about twice as much to their defect reduction as the spontaneous recovery. Goal Attainment Scores were significantly and positively correlated with the total defect reduction (p = 0.01), percentage increase reading speed was significantly and positively correlated with the defect reduction induced by training (epoch 1: p = 0.0044; epoch 2: p = 0.023). Visual training adds significantly to the spontaneous recovery of visual field defects, both during training in the early and the chronic stroke phase. However, field recovery as a result of training in this subacute phase was as large as in the chronic phase. This suggests that patients benefited primarily of early onset training by gaining access to a larger visual field sooner.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Whether rehabilitation after stroke profits from an early start is difficult to establish as the contributions of spontaneous recovery and treatment are difficult to tease apart. Here, we use a novel training design to dissociate these components for visual rehabilitation of subacute stroke patients with visual field defects such as hemianopia. Visual discrimination training was started within 6 weeks after stroke in 17 patients. Spontaneous and training-induced recoveries were distinguished by training one-half of the defect for 8 weeks, while monitoring spontaneous recovery in the other (control) half of the defect. Next, trained and control regions were swapped, and training continued for another 8 weeks. The same paradigm was also applied to seven chronic patients for whom spontaneous recovery can be excluded and changes in the control half of the defect point to a spillover effect of training. In both groups, field stability was assessed during a no-intervention period. Defect reduction was significantly greater in the trained part of the defect than in the simultaneously untrained part of the defect irrespective of training onset (p = 0.001). In subacute patients, training contributed about twice as much to their defect reduction as the spontaneous recovery. Goal Attainment Scores were significantly and positively correlated with the total defect reduction (p = 0.01), percentage increase reading speed was significantly and positively correlated with the defect reduction induced by training (epoch 1: p = 0.0044; epoch 2: p = 0.023). Visual training adds significantly to the spontaneous recovery of visual field defects, both during training in the early and the chronic stroke phase. However, field recovery as a result of training in this subacute phase was as large as in the chronic phase. This suggests that patients benefited primarily of early onset training by gaining access to a larger visual field sooner. |
Douwe P Bergsma; Mies van Genderen; Carlien Roelofzen; Serge O Dumoulin; Alessio Fracasso; Giorgio L Porro; Marnix Naber Gaze-contingent flicker pupil perimetry detects scotomas in patients with cerebral visual impairments or glaucoma Journal Article Frontiers in Neurology, 9 , pp. 1–12, 2018. @article{Bergsma2018, title = {Gaze-contingent flicker pupil perimetry detects scotomas in patients with cerebral visual impairments or glaucoma}, author = {Douwe P Bergsma and Mies van Genderen and Carlien Roelofzen and Serge O Dumoulin and Alessio Fracasso and Giorgio L Porro and Marnix Naber}, doi = {10.3389/fneur.2018.00558}, year = {2018}, date = {2018-01-01}, journal = {Frontiers in Neurology}, volume = {9}, pages = {1--12}, abstract = {Background: The pupillary light reflex is weaker for stimuli presented inside as compared to outside absolute scotomas. Pupillograph perimetry could thus be an objective measure of impaired visual processing. However, the diagnostic accuracy in detecting scotomas has remained unclear. We quantitatively investigated the accuracy of a novel form of pupil perimetry. Methods: The new perimetry method, termed gaze-contingent flicker pupil perimetry, consists of the repetitive on, and off flickering of a bright disk (2 hz; 320 cd/m2; 4◦ diameter) on a gray background (160 cd/m2) for 4 seconds per stimulus location. The disk evokes continuous pupil oscillations at the same rate as its flicker frequency, and the oscillatory power of the pupil reflects visual sensitivity. We monocularly presented the disk at a total of 80 locations in the central visual field (max. 15◦). The location of the flickering disk moved along with gaze to reduce confounds of eye movements (gaze-contingent paradigm). The test lasted ∼5min per eye and was performed on 7 patients with cerebral visual impairment (CVI), 8 patients with primary open angle glaucoma (age textgreater 45), and 14 healthy, age/gender-matched controls. Results: For all patients, pupil oscillation power (FFT based response amplitude to flicker) was significantly weaker when the flickering disk was presented in the impaired as compared to the intact visual field (CVI: 12%}, keywords = {}, pubstate = {published}, tppubtype = {article} } Background: The pupillary light reflex is weaker for stimuli presented inside as compared to outside absolute scotomas. Pupillograph perimetry could thus be an objective measure of impaired visual processing. However, the diagnostic accuracy in detecting scotomas has remained unclear. We quantitatively investigated the accuracy of a novel form of pupil perimetry. Methods: The new perimetry method, termed gaze-contingent flicker pupil perimetry, consists of the repetitive on, and off flickering of a bright disk (2 hz; 320 cd/m2; 4◦ diameter) on a gray background (160 cd/m2) for 4 seconds per stimulus location. The disk evokes continuous pupil oscillations at the same rate as its flicker frequency, and the oscillatory power of the pupil reflects visual sensitivity. We monocularly presented the disk at a total of 80 locations in the central visual field (max. 15◦). The location of the flickering disk moved along with gaze to reduce confounds of eye movements (gaze-contingent paradigm). The test lasted ∼5min per eye and was performed on 7 patients with cerebral visual impairment (CVI), 8 patients with primary open angle glaucoma (age textgreater 45), and 14 healthy, age/gender-matched controls. Results: For all patients, pupil oscillation power (FFT based response amplitude to flicker) was significantly weaker when the flickering disk was presented in the impaired as compared to the intact visual field (CVI: 12% |
Jean-Baptiste Bernard; Susana T L Chung The role of external features in face recognition with central vision loss Journal Article Optometry and Vision Science, 93 (5), pp. 510–520, 2016. @article{Bernard2016b, title = {The role of external features in face recognition with central vision loss}, author = {Jean-Baptiste Bernard and Susana T L Chung}, doi = {http://dx.doi.org/10.1289/ehp.1002503}, year = {2016}, date = {2016-01-01}, journal = {Optometry and Vision Science}, volume = {93}, number = {5}, pages = {510--520}, abstract = {PURPOSE: We evaluated how the performance of recognizing familiar face images depends on the internal (eyebrows, eyes, nose, mouth) and external face features (chin, outline of face, hairline) in individuals with central vision loss. METHODS: In experiment 1, we measured eye movements for four observers with central vision loss to determine whether they fixated more often on the internal or the external features of face images while attempting to recognize the images. We then measured the accuracy for recognizing face images that contained only the internal, only the external, or both internal and external features (experiment 2) and for hybrid images where the internal and external features came from two different source images (experiment 3) for five observers with central vision loss and four age-matched control observers. RESULTS: When recognizing familiar face images, approximately 40% of the fixations of observers with central vision loss was centered on the external features of faces. The recognition accuracy was higher for images containing only external features (66.8 ± 3.3% correct) than for images containing only internal features (35.8 ± 15.0%), a finding contradicting that of control observers. For hybrid face images, observers with central vision loss responded more accurately to the external features (50.4 ± 17.8%) than to the internal features (9.3 ± 4.9%), whereas control observers did not show the same bias toward responding to the external features. CONCLUSIONS: Contrary to people with normal vision who rely more on the internal features of face images for recognizing familiar faces, individuals with central vision loss show a higher dependence on using external features of face images.}, keywords = {}, pubstate = {published}, tppubtype = {article} } PURPOSE: We evaluated how the performance of recognizing familiar face images depends on the internal (eyebrows, eyes, nose, mouth) and external face features (chin, outline of face, hairline) in individuals with central vision loss. METHODS: In experiment 1, we measured eye movements for four observers with central vision loss to determine whether they fixated more often on the internal or the external features of face images while attempting to recognize the images. We then measured the accuracy for recognizing face images that contained only the internal, only the external, or both internal and external features (experiment 2) and for hybrid images where the internal and external features came from two different source images (experiment 3) for five observers with central vision loss and four age-matched control observers. RESULTS: When recognizing familiar face images, approximately 40% of the fixations of observers with central vision loss was centered on the external features of faces. The recognition accuracy was higher for images containing only external features (66.8 ± 3.3% correct) than for images containing only internal features (35.8 ± 15.0%), a finding contradicting that of control observers. For hybrid face images, observers with central vision loss responded more accurately to the external features (50.4 ± 17.8%) than to the internal features (9.3 ± 4.9%), whereas control observers did not show the same bias toward responding to the external features. CONCLUSIONS: Contrary to people with normal vision who rely more on the internal features of face images for recognizing familiar faces, individuals with central vision loss show a higher dependence on using external features of face images. |