EyeLink Clinical and Oculomotor Eye-Tracking Publications
EyeLink clinical and oculomotor research publications up until 2023 (with some early 2024s) are listed below by year. You can search the publications using keywords such as Saccadic Adaptation, Schizophrenia, Nystagmus, etc. You can also search for individual author names, and limit searches by year (choose the year then click the search button). If we missed any EyeLink clinical or oculomotor articles, please email us!
2016 |
Jean-Baptiste Bernard; Susana T. L. Chung The role of external features in face recognition with central vision loss Journal Article In: Optometry and Vision Science, vol. 93, no. 5, pp. 510–520, 2016. @article{Bernard2016a, 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. |
Sabrina Boll; Marie Bartholomaeus; Ulrike Peter; Ulrike Lupke; Matthias Gamer Attentional mechanisms of social perception are biased in social phobia Journal Article In: Journal of Anxiety Disorders, vol. 40, pp. 83–93, 2016. @article{Boll2016a, Previous studies of social phobia have reported an increased vigilance to social threat cues but also an avoidance of socially relevant stimuli such as eye gaze. The primary aim of this study was to examine attentional mechanisms relevant for perceiving social cues by means of abnormalities in scanning of facial features in patients with social phobia. In two novel experimental paradigms, patients with social phobia and healthy controls matched on age, gender and education were compared regarding their gazing behavior towards facial cues. The first experiment was an emotion classification paradigm which allowed for differentiating reflexive attentional shifts from sustained attention towards diagnostically relevant facial features. In the second experiment, attentional orienting by gaze direction was assessed in a gaze-cueing paradigm in which non-predictive gaze cues shifted attention towards or away from subsequently presented targets. We found that patients as compared to controls reflexively oriented their attention more frequently towards the eyes of emotional faces in the emotion classification paradigm. This initial hypervigilance for the eye region was observed at very early attentional stages when faces were presented for 150 ms, and persisted when facial stimuli were shown for 3 s. Moreover, a delayed attentional orienting into the direction of eye gaze was observed in individuals with social phobia suggesting a differential time course of eye gaze processing in patients and controls. Our findings suggest that basic mechanisms of early attentional exploration of social cues are biased in social phobia and might contribute to the development and maintenance of the disorder. |
Sabrina Boll; Matthias Gamer Psychopathic traits affect the visual exploration of facial expressions Journal Article In: Biological Psychology, vol. 117, pp. 194–201, 2016. @article{Boll2016, Deficits in emotional reactivity and recognition have been reported in psychopathy. Impaired attention to the eyes along with amygdala malfunctions may underlie these problems. Here, we investigated how different facets of psychopathy modulate the visual exploration of facial expressions by assessing personality traits in a sample of healthy young adults using an eye-tracking based face perception task. Fearless Dominance (the interpersonal-emotional facet of psychopathy) and Coldheartedness scores predicted reduced face exploration consistent with findings on lowered emotional reactivity in psychopathy. Moreover, participants high on the social deviance facet of psychopathy ('Self-Centered Impulsivity') showed a reduced bias to shift attention towards the eyes. Our data suggest that facets of psychopathy modulate face processing in healthy individuals and reveal possible attentional mechanisms which might be responsible for the severe impairments of social perception and behavior observed in psychopathy. |
Aurélie Calabrèse; Jean-Baptiste Bernard; Géraldine Faure; Louis Hoffart; Eric Castet Clustering of eye fixations: A new oculomotor determinant of reading speed in maculopathy Journal Article In: Investigative Ophthalmology & Visual Science, vol. 57, no. 7, pp. 3192–3202, 2016. @article{Calabrese2016, Purpose: To describe and quantify a largely unnoticed oculomotor pattern that often occurs when patients with central field loss (CFL) read continuous text: Horizontal distribution of eye fixations dramatically varies across sentences and often reveals clusters. Also to statistically analyze the effect of this new factor on reading speed while controlling for the effect of saccadic amplitude (measured in letters per forward saccade, L/FS), an established oculomotor effect. Methods: Quantification of nonuniformity of eye fixations (NUF factor) was based on statistical analysis of the curvature of fixation distributions. Linear mixed-effects analyses were performed to predict reading speed from oculomotor factors based on eye movements of 34 AMD and 4 Stargardt patients (better eye decimal acuity from 0.08 to 0.3). Single-line French sentences were read aloud by these patients, who all had a dense scotoma covering the fovea as assessed with MP1 microperimetry. Results: Nonuniformity of fixations is a strong determinant of reading speed (−0.76 log units; 95% confidence interval [CI] [−0.86, −0.66]). This effect is not confounded with the effect of L/FS. The per sentence proportion of trials with clustering is predicted by the frequency of occurrence of the lowest-frequency word in each sentence. Conclusions: The NUF factor is a new oculomotor predictor of reading speed. This effect is independent of the effect of L/FS. Reading performance, as well as motivation to read, might be enhanced if new visual aids or automatic text simplification were used to reduce the occurrence of fixation clustering. © |
Irene Ablinger; Ralph Radach Diverging receptive and expressive word processing mechanisms in a deep dyslexic reader Journal Article In: Neuropsychologia, vol. 81, pp. 12–21, 2016. @article{Ablinger2016, 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. |
Serguei V. Astafiev; Kristina L. Zinn; Gordon L. Shulman; Maurizio Corbetta Exploring the physiological correlates of chronic mild traumatic brain injury symptoms Journal Article In: NeuroImage: Clinical, vol. 11, pp. 10–19, 2016. @article{Astafiev2016, 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. |
Bobby Azarian; Elizabeth G. Esser; Matthew S. Peterson Evidence from the eyes: Threatening postures hold attention Journal Article In: Psychonomic Bulletin & Review, vol. 23, no. 3, pp. 764–770, 2016. @article{Azarian2016, 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. |
Petra Sinn; Ralf Engbert Small saccades versus microsaccades: Experimental distinction and model-based unification Journal Article In: Vision Research, vol. 118, pp. 132–143, 2016. @article{Sinn2016, Natural vision is characterized by alternating sequences of rapid gaze shifts (saccades) and fixations. During fixations, microsaccades and slower drift movements occur spontaneously, so that the eye is never motionless. Theoretical models of fixational eye movements predict that microsaccades are dynamically coupled to slower drift movements generated immediately before microsaccades, which might be used as a criterion to distinguish microsaccades from small voluntary saccades. Here we investigate a sequential scanning task, where participants generate goal-directed saccades and microsaccades with overlapping amplitude distributions. We show that properties of microsaccades are correlated with precursory drift motion, while amplitudes of goal-directed saccades do not dependent on previous drift epochs. We develop and test a mathematical model that integrates goal-directed and fixational eye movements, including microsaccades. Using model simulations, we reproduce the experimental finding of correlations within fixational eye movement components (i.e., between physiological drift and microsaccades) but not between goal-directed saccades and fixational drift motion. These results lend support to a functional difference between microsaccades and goal-directed saccades, while, at the same time, both types of behavior may be part of an oculomotor continuum that is quantitatively described by our mathematical model. |
David Souto; Karl R. Gegenfurtner; Alexander C. Schütz Saccade adaptation and visual uncertainty Journal Article In: Frontiers in Human Neuroscience, vol. 10, pp. 227, 2016. @article{Souto2016, Visual uncertainty may affect saccade adaptation in two complementary ways. First, an ideal adaptor should take into account the reliability of visual information for determining the amount of correction, predicting that increasing visual uncertainty should decrease adaptation rates. We tested this by comparing observers' direction discrimination and adaptation rates in an intra-saccadic-step paradigm. Second, clearly visible target steps may generate a slower adaptation rate since the error can be attributed to an external cause, instead of an internal change in the visuo-motor mapping that needs to be compensated. We tested this prediction by measuring saccade adaptation to different step sizes. Most remarkably, we found little correlation between estimates of visual uncertainty and adaptation rates and no slower adaptation rates with more visible step sizes. Additionally, we show that for low contrast targets backward steps are perceived as stationary after the saccade, but that adaptation rates are independent of contrast. We suggest that the saccadic system uses different position signals for adapting dysmetric saccades and for generating a trans-saccadic stable visual percept, explaining that saccade adaptation is found to be independent of visual uncertainty. |
Sara Spotorno; Guillaume S. Masson; Anna Montagnini Fixational saccades during grating detection and discrimination Journal Article In: Vision Research, vol. 118, pp. 105–118, 2016. @article{Spotorno2016, We investigated the patterns of fixational saccades in human observers performing two classical perceptual tasks: grating detection and discrimination. First, participants were asked to detect a vertical or tilted grating with one of three spatial frequencies and one of four luminance contrast levels. In the second experiment, participants had to discriminate the spatial frequency of two supra-threshold gratings. The gratings were always embedded in additive, high- or low-contrast pink noise. We observed that the patterns of fixational saccades were highly idiosyncratic among participants. Moreover, during the grating detection task, the amplitude and the number of saccades were inversely correlated with stimulus visibility. We did not find a systematic relationship between saccade parameters and grating frequency, apart from a slight decrease of saccade amplitude during grating discrimination with higher spatial frequencies. No consistent changes in the number and amplitude of fixational saccades with performance accuracy were reported. Surprisingly, during grating detection, saccade number and amplitude were similar in grating-with-noise and noise-only displays. Grating orientation did not affect substantially saccade direction in either task. The results challenge the idea that, when analyzing low-level spatial properties of visual stimuli, fixational saccades can be adapted in order to extract task-relevant information optimally. Rather, saccadic patterns seem to be overall modulated by task context, stimulus visibility and individual variability. |
Maria Steffens; B. Becker; C. Neumann; Anna-Maria Kasparbauer; Inga Meyhöfer; Bernd Weber; Mitul A. Mehta; R. Hurlemann; Ulrich Ettinger Effects of ketamine on brain function during smooth pursuit eye movements Journal Article In: Human Brain Mapping, vol. 37, no. 11, pp. 4047–4060, 2016. @article{Steffens2016, The uncompetitive NMDA receptor antagonist ketamine has been proposed to model symptoms of psychosis. Smooth pursuit eye movements (SPEM) are an established biomarker of schizophrenia. SPEM performance has been shown to be impaired in the schizophrenia spectrum and during ketamine administration in healthy volunteers. However, the neural mechanisms mediating SPEM impairments during ketamine administration are unknown. In a counter-balanced, placebo-controlled, double-blind, within-subjects design, 27 healthy participants received intravenous racemic ketamine (100 ng/mL target plasma concentration) on one of two assessment days and placebo (intravenous saline) on the other. Participants performed a block-design SPEM task during functional magnetic resonance imaging (fMRI) at 3 Tesla field strength. Self-ratings of psychosis-like experiences were obtained using the Psychotomimetic States Inventory (PSI). Ketamine administration induced psychosis-like symptoms, during ketamine infusion, participants showed increased ratings on the PSI dimensions cognitive disorganization, delusional thinking, perceptual distortion and mania. Ketamine led to robust deficits in SPEM performance, which were accompanied by reduced blood oxygen level dependent (BOLD) signal in the SPEM network including primary visual cortex, area V5 and the right frontal eye field (FEF), compared to placebo. A measure of connectivity with V5 and FEF as seed regions, however, was not significantly affected by ketamine. These results are similar to the deviations found in schizophrenia patients. Our findings support the role of glutamate dysfunction in impaired smooth pursuit performance and the use of ketamine as a pharmacological model of psychosis, especially when combined with oculomotor biomarkers. |
Martin Szinte; Donatas Jonikaitis; Martin Rolfs; Patrick Cavanagh; Heiner Deubel Presaccadic motion integration between current and future retinotopic locations of attended objects Journal Article In: Journal of Neurophysiology, vol. 116, no. 4, pp. 1592–1602, 2016. @article{Szinte2016, Object tracking across eye movements is thought to rely on pre-saccadic updating of attention between the object's current and its "remapped" location (i.e., the post-saccadic retinotopic location). Here we report evidence for a bi-focal, pre-saccadic sampling between these two positions. While preparing a saccade, participants viewed four spatially separated random dot kinematograms, one of which was cued by a colored flash. They reported the direction of a coherent motion signal at the cued location while a second signal occurred simultaneously either at the cue's remapped location or at one of several control locations. Motion integration between the signals occurred only when the two motion signals were congruent and were shown at the cue and at its remapped location. This shows that the visual system integrates features between both the current and the future retinotopic locations of an attended object, and that such pre-saccadic sampling is feature-specific. |
Jérôme Tagu; Karine Doré-Mazars; Christelle Lemoine-Lardennois; Dorine Vergilino-Perez How eye dominance strength modulates the influence of a distractor on saccade accuracy Journal Article In: Investigative Ophthalmology & Visual Science, vol. 57, no. 2, pp. 534–543, 2016. @article{Tagu2016, PURPOSE. Neuroimaging studies have shown that the dominant eye is linked preferentially to the ipsilateral primary visual cortex. However, its role in perception still is misunderstood. We examined the influence of eye dominance and eye dominance strength on saccadic parameters, contrasting stimulations presented in the two hemifields. METHODS. Participants with contrasted eye dominance (left or right) and eye dominance strength (strong or weak) were asked to make a saccade toward a target displayed at 5degree or 7degree left or right of a fixation cross. In some trials, a distractor at 3degree of eccentricity also was displayed either in the same hemifield as the target (to induce a global effect on saccade amplitude) or in the opposite hemifield (to induce a remote distractor effect on saccade latency). RESULTS. Eye dominance did influence saccade amplitude as participants with strong eye dominance showed more accurate saccades toward the target (weaker global effect) in the hemifield contralateral to the dominant eye than in the ipsilateral one. Such asymmetry was not found in participants with weak eye dominance or when a remote distractor was used. CONCLUSIONS. We show that eye dominance strength influences saccade target selection. We discuss several arguments supporting the view that such advantage may be linked to the relationship between the dominant eye and ipsilateral hemisphere. |
Tobias Talanow; Anna-Maria Kasparbauer; Maria Steffens; Inga Meyhöfer; Bernd Weber; Nikolaos Smyrnis; Ulrich Ettinger Facing competition: Neural mechanisms underlying parallel programming of antisaccades and prosaccades Journal Article In: Brain and Cognition, vol. 107, pp. 37–47, 2016. @article{Talanow2016, The antisaccade task is a prominent tool to investigate the response inhibition component of cognitive control. Recent theoretical accounts explain performance in terms of parallel programming of exogenous and endogenous saccades, linked to the horse race metaphor. Previous studies have tested the hypothesis of competing saccade signals at the behavioral level by selectively slowing the programming of endogenous or exogenous processes e.g. by manipulating the probability of antisaccades in an experimental block. To gain a better understanding of inhibitory control processes in parallel saccade programming, we analyzed task-related eye movements and blood oxygenation level dependent (BOLD) responses obtained using functional magnetic resonance imaging (fMRI) at 3T from 16 healthy participants in a mixed antisaccade and prosaccade task. The frequency of antisaccade trials was manipulated across blocks of high (75%) and low (25%) antisaccade frequency. In blocks with high antisaccade frequency, antisaccade latencies were shorter and error rates lower whilst prosaccade latencies were longer and error rates were higher. At the level of BOLD, activations in the task-related saccade network (left inferior parietal lobe, right inferior parietal sulcus, left precentral gyrus reaching into left middle frontal gyrus and inferior frontal junction) and deactivations in components of the default mode network (bilateral temporal cortex, ventromedial prefrontal cortex) compensated increased cognitive control demands. These findings illustrate context dependent mechanisms underlying the coordination of competing decision signals in volitional gaze control. |
Yasuo Terao; Hideki Fukuda; Shinnichi Tokushuge; Yoshiko Nomura; Ritsuko Hanajima; Yoshikazu Ugawa Saccade abnormalities associated with focal cerebral lesions – How cortical and basal ganglia commands shape saccades in humans Journal Article In: Clinical Neurophysiology, vol. 127, no. 8, pp. 2953–2967, 2016. @article{Terao2016, Objective: To study saccade abnormalities associated with focal cerebral lesions, including the cerebral cortex and basal ganglia (BG). Methods: We studied the latency and amplitude of reflexive and voluntary saccades in 37 patients with focal lesions of the frontal and parietal cortices and BG (caudate and putamen), and 51 age-matched controls, along with the ability to inhibit unwanted reflexive saccades. Results: Latencies of reflexive saccades were prolonged in patients with parietal lesions involving the parietal eye field (PEF), whereas their amplitude was decreased with parietal or putaminal lesions. In contrast, latency of voluntary saccades was prolonged and their success rate reduced with frontal lesions including the frontal eye field (FEF) or its outflow tract as well as the dorsolateral/medial prefrontal cortex, and caudate lesions, whereas their amplitude was decreased with parietal lesions. Inhibitory control of reflexive saccades was impaired with frontal, caudate and, less prominently, parietal lesions. Conclusions: PEF is important in triggering reflexive saccades, also determining their amplitude. Whereas FEF and the caudate emit commands for initiating voluntary saccades, their amplitude is mainly determined by PEF. Commands not only from FEF and dorsolateral/medial prefrontal cortex but also from the caudate and PEF serve to inhibit unnecessary reflexive saccades. Significance: The findings suggested how cortical and BG commands shape reflexive and voluntary saccades in humans. |
Xiaoguang Tian; Masatoshi Yoshida; Ziad M. Hafed A microsaccadic account of attentional capture and inhibition of return in Posner cueing Journal Article In: Frontiers in Systems Neuroscience, vol. 10, pp. 23, 2016. @article{Tian2016, Microsaccades exhibit systematic oscillations in direction after spatial cueing, and these oscillations correlate with facilitatory and inhibitory changes in behavioral performance in the same tasks. However, independent of cueing, facilitatory and inhibitory changes in visual sensitivity also arise pre-microsaccadically. Given such pre-microsaccadic modulation, an imperative question to ask becomes: how much of task performance in spatial cueing may be attributable to these peri-movement changes in visual sensitivity? To investigate this question, we adopted a theoretical approach. We developed a minimalist model in which: (1) microsaccades are repetitively generated using a rise-to-threshold mechanism, and (2) pre-microsaccadic target onset is associated with direction-dependent modulation of visual sensitivity, as found experimentally. We asked whether such a model alone is sufficient to account for performance dynamics in spatial cueing. Our model not only explained fine-scale microsaccade frequency and direction modulations after spatial cueing, but it also generated classic facilitatory (i.e., attentional capture) and inhibitory [i.e., inhibition of return (IOR)] effects of the cue on behavioral performance. According to the model, cues reflexively reset the oculomotor system, which unmasks oscillatory processes underlying microsaccade generation; once these oscillatory processes are unmasked, "attentional capture" and "IOR" become direct outcomes of pre-microsaccadic enhancement or suppression, respectively. Interestingly, our model predicted that facilitatory and inhibitory effects on behavior should appear as a function of target onset relative to microsaccades even without prior cues. We experimentally validated this prediction for both saccadic and manual responses. We also established a potential causal mechanism for the microsaccadic oscillatory processes hypothesized by our model. We used retinal-image stabilization to experimentally control instantaneous foveal motor error during the presentation of peripheral cues, and we found that post-cue microsaccadic oscillations were severely disrupted. This suggests that microsaccades in spatial cueing tasks reflect active oculomotor correction of foveal motor error, rather than presumed oscillatory covert attentional processes. Taken together, our results demonstrate that peri-microsaccadic changes in vision can go a long way in accounting for some classic behavioral phenomena. |
Helena X. Wang; Shlomit Yuval-Greenberg; David J. Heeger Suppressive interactions underlying visually evoked fixational saccades Journal Article In: Vision Research, vol. 118, no. 9, pp. 70–82, 2016. @article{Wang2016d, Small saccades occur frequently during fixation, and are coupled to changes in visual stimulation and cognitive state. Neurophysiologically, fixational saccades reflect neural activity near the foveal region of a continuous visuomotor map. It is well known that competitive interactions between neurons within visuomotor maps contribute to target selection for large saccades. Here we asked how such interactions in visuomotor maps shape the rate and direction of small fixational saccades. We measured fixational saccades during periods of prolonged fixation while presenting pairs of visual stimuli (parafoveal: 0.8° eccentricity; peripheral: 5° eccentricity) of various contrasts. Fixational saccade direction was biased toward locations of parafoveal stimuli but not peripheral stimuli, ~100-250 ms following stimulus onset. The rate of fixational saccades toward parafoveal stimuli (congruent saccades) increased systematically with parafoveal stimulus contrast, and was suppressed by the simultaneous presentation of a peripheral stimulus. The suppression was best characterized as a combination of two processes: a subtractive suppression of the overall fixational saccade rate and a divisive suppression of the direction bias. These results reveal the nature of suppressive interactions within visuomotor maps and constrain models of the population code for fixational saccades. |
Kim Wende; Laetitia Theunissen; Marcus Missal Anticipation of physical causality guides eye movements Journal Article In: Journal of Eye Movement Research, vol. 9, no. 2, pp. 1–9, 2016. @article{Wende2016, Causality is a unique feature of human perception. We present here a behavioral investigation of the influence of physical causality during visual pursuit of object collisions. Pursuit and saccadic eye movements of human subjects were recorded during ocular pursuit of two concurrently launched targets, one that moved according to the laws of Newtonian mechanics (the causal target) and the other one that moved in a physically implausible direction (the non-causal target). We found that anticipation of collision evoked early smooth pursuit decelerations. Saccades to non-causal targets were hypermetric and had latencies longer than saccades to causal targets. In conclusion, before and after a collision of two moving objects the oculomotor system implicitly predicts upcoming physically plausible target trajectories. |
Farahnaz A. Wick; Tyler W. Garaas; Marc Pomplun Saccadic adaptation alters the attentional field Journal Article In: Frontiers in Human Neuroscience, vol. 10, pp. 568, 2016. @article{Wick2016, It is currently unknown whether changes to the oculomotor system can induce changes to the distribution of spatial attention around a fixated target. Previous studies have used perceptual performance tasks to show that adaptation of saccadic eye movements affects dynamic properties of visual attention, in particular, attentional shifts to a cued location. In this study, we examined the effects of saccadic adaptation on the static distribution of visual attention around fixation (attentional field). We used the classic double step adaptation procedure and a flanker task to test for differences in the attentional field after forward and backward adaptation. RT measures revealed that the shape of the attentional field changed significantly after backward adaptation as shown through altered interference from distracters at different eccentricities but not after forward adaptation. This finding reveals that modification of saccadic amplitudes can affect metrics of not only dynamic properties of attention but also its static properties. A major implication is that the neural mechanisms underlying fundamental selection mechanisms and the oculomotor system can reweight each other. |
Esther X. W. Wu; Fook-Kee Chua; Shih-Cheng Yen Saccade plan overlap and cancellation during free viewing Journal Article In: Vision Research, vol. 127, pp. 122–131, 2016. @article{Wu2016a, In the current study, we examined how the saccadic system responds when visual information changes dynamically in our environment. Previous studies, using the double-step task, have shown that (a) saccade plans could overlap, such that saccade preparation to an object started even while the saccade preparation to another object was ongoing, and (b) saccade plans could be cancelled before they were completed. In these studies, saccade targets were restricted to a few, experimenter-defined locations. Here, we examined whether saccade plan overlap and cancellation mechanisms could be observed in free-viewing conditions. For each trial, we constructed sets of two images, each containing five objects. All objects have unique positions. Image 1 was presented for several fixations, before Image 2 was presented during a fixation, presumably while a saccade plan to an object in Image 1 was ongoing. There were two crucial findings: (a) First, the saccade immediately following the transition was sometimes executed towards objects in Image 2, and not an object in Image 1, suggesting that the earlier saccade plan to an Image 1 object had been cancelled. Second, analysis of the temporal data also suggested that preparation of the first post-transition saccade started before an earlier saccade plan to an Image 1 object was executed, implying that saccade plans overlapped. |
Chuyao Yan; Tao He; Raymond M. Klein; Zhiguo Wang Predictive remapping gives rise to environmental inhibition of return Journal Article In: Psychonomic Bulletin & Review, vol. 23, no. 6, pp. 1860–1866, 2016. @article{Yan2016a, Neurons in various brain regions predictively respond to stimuli that will be brought to their receptive fields by an impending eye movement. This neural mechanism, known as predictive remapping, has been suggested to underlie spatial constancy. Inhibition of return (IOR) is a bias against recently attended locations. The present study examined whether predictive remapping is a mechanism underlying IOR effects observed in environmental coordinates. The participant made saccades to a peripheral location after an IOR effect had been elicited by an onset cue and discriminated a target presented around the time of saccade onset. Immediately before the required saccade, IOR emerged at the retinal locus that would be brought to the cued location. A second task in which the participant maintained fixation during the entire trial ruled out the possibility that this IOR effect was simply the spillover of IOR from the cued location. These findings, for the first time, provide direct behavioral evidence that predictive remapping is a mechanism underlying environmental IOR. |
Theodoros P. Zanos; Patrick J. Mineault; Daniel Guitton; Christopher C. Pack Mechanisms of saccadic suppression in primate cortical area V4 Journal Article In: Journal of Neuroscience, vol. 36, no. 35, pp. 9227–9239, 2016. @article{Zanos2016, Psychophysical studies have shown that subjects are often unaware of visual stimuli presented around the time of an eye movement. This saccadic suppression is thought to be a mechanism for maintaining perceptual stability. The brain might accomplish saccadic suppression by reducing the gain of visual responses to specific stimuli or by simply suppressing firing uniformly for all stimuli. Moreover, the suppression might be identical across the visual field or concentrated at specific points. To evaluate these possibilities, we recorded from individual neurons in cortical area V4 of nonhuman primates trained to execute saccadic eye movements. We found that both modes of suppression were evident in the visual responses of these neurons and that the two modes showed different spatial and temporal profiles: while gain changes started earlier and were more widely distributed across visual space, nonspecific suppression was found more often in the peripheral visual field, after the completion of the saccade. Peripheral suppression was also associated with increased noise correlations and stronger local field potential oscillations in the α frequency band. This pattern of results suggests that saccadic suppression shares some of the circuitry responsible for allocating voluntary attention. SIGNIFICANCE STATEMENT We explore our surroundings by looking at things, but each eye movement that we make causes an abrupt shift of the visual input. Why doesn't the world look like a film recorded on a shaky camera? The answer in part is a brain mechanism called saccadic suppression, which reduces the responses of visual neurons around the time of each eye movement. Here we reveal several new properties of the underlying mechanisms. First, the suppression operates differently in the central and peripheral visual fields. Second, it appears to be controlled by oscillations in the local field potentials at frequencies traditionally associated with attention. These results suggest that saccadic suppression shares the brain circuits responsible for actively ignoring irrelevant stimuli. |
Paul Zerr; Katharine N. Thakkar; Siarhei Uzunbajakau; Stefan Van der Stigchel Error compensation in random vector double step saccades with and without global adaptation Journal Article In: Vision Research, vol. 127, pp. 141–151, 2016. @article{Zerr2016, In saccade sequences without visual feedback endpoint errors pose a problem for subsequent saccades. Accurate error compensation has previously been demonstrated in double step saccades (DSS) and is thought to rely on a copy of the saccade motor vector. However, these studies typically use fixed target vectors on each trial, calling into question the generalizability of the findings due to the high stimulus predictability. We present a random walk DSS paradigm (random target vector amplitudes and directions) to provide a more complete, realistic and generalizable description of error compensation in saccade sequences. We regressed the vector between the endpoint of the second saccade and the endpoint of a hypothetical second saccade that does not take first saccade error into account on the ideal compensation vector. This provides a direct and complete estimation of error compensation in DSS. We observed error compensation with varying stimulus displays that was comparable to previous findings. We also employed this paradigm to extend experiments that showed accurate compensation for systematic undershoots after specific-vector saccade adaptation. Utilizing the random walk paradigm for saccade adaptation by Rolfs et al. (2010) together with our random walk DSS paradigm we now also demonstrate transfer of adaptation from reactive to memory guided saccades for global saccade adaptation. We developed a new, generalizable DSS paradigm with unpredictable stimuli and successfully employed it to verify, replicate and extend previous findings, demonstrating that endpoint errors are compensated for saccades in all directions and variable amplitudes. |
Eckart Zimmermann Spatiotopic buildup of saccade target representation depends on target size Journal Article In: Journal of Vision, vol. 16, no. 15, pp. 11, 2016. @article{Zimmermann2016, How we maintain spatial stability across saccade eye movements is an open question in visual neuroscience. A phenomenon that has received much attention in the field is our seemingly poor ability to discriminate the direction of transsaccadic target displacements. We have recently shown that discrimination performance increases the longer the saccade target has been previewed before saccade execution (Zimmermann, Morrone, & Burr, 2013). We have argued that the spatial representation of briefly presented stimuli is weak but that a strong representation is needed for transsaccadic, i.e., spatiotopic localization. Another factor that modulates the representation of saccade targets is stimulus size. The representation of spatially extended targets is more noisy than that of point-like targets. Here, I show that theincreaseintranssaccadic displacement discrimination as a function of saccade target preview duration depends on target size. This effect was found for spatially extended targets—thus replicating the results of Zimmermann et al. (2013)— but not for point-like targets. An analysis of saccade parameters revealed that the constant error for reaching the saccade target was bigger for spatially extended than for point-like targets, consistent with weaker representation of bigger targets. These results show that transsaccadic displacement discrimination becomes accurate when saccade targets are spatially extended and presented longer, thus resembling closer stimuli in real-world environments. |
Eckart Zimmermann; M. Concetta Morrone; David C. Burr Adaptation to size affects saccades with long but not short latencies Journal Article In: Journal of Vision, vol. 16, no. 7, pp. 2, 2016. @article{Zimmermann2016a, Maintained exposure to a specific stimulus property— such as size, color, or motion—induces perceptual adaptation aftereffects, usually in the opposite direction to that of the adaptor. Here we studied how adaptation to size affects perceived position and visually guided action (saccadic eye movements) to that position. Subjects saccaded to the border of a diamond-shaped object after adaptation to a smaller diamond shape. For saccades in the normal latency range, amplitudes decreased, consistent with saccading to a larger object. Short-latency saccades, however, tended to be affected less by the adaptation, suggesting that they were only partly triggered by a signal representing the illusory target position. We also tested size perception after adaptation, followed by a mask stimulus at the probe location after various delays. Similar size adaptation magnitudes were found for all probe-mask delays. In agreement with earlier studies, these results suggest that the duration of the saccade latency period determines the reference frame that codes the probe location. |
Eckart Zimmermann; Ralph Weidner; R. O. Abdollahi; Gereon R. Fink Spatiotopic adaptation in visual areas Journal Article In: Journal of Neuroscience, vol. 36, no. 37, pp. 9526–9534, 2016. @article{Zimmermann2016b, The ability to perceive the visual world around us as spatially stable despite frequent eye movements is one of the long-standing mysteries of neuroscience. The existence of neural mechanisms processing spatiotopic information is indispensable for a successful interaction with the external world. However, how the brain handles spatiotopic information remains a matter of debate. We here combined behavioral and fMRI adaptation to investigate the coding of spatiotopic information in the human brain. Subjects were adapted by a prolonged presentation of a tilted grating. Thereafter, they performed a saccade followed by the brief presentation of a probe. This procedure allowed dissociating adaptation aftereffects at retinal and spatiotopic positions. We found significant behavioral and functional adaptation in both retinal and spatiotopic positions, indicating information transfer into a spatiotopic coordinate system. The brain regions involved were located in ventral visual areas V3, V4, and VO. Our findings suggest that spatiotopic representations involved in maintaining visual stability are constructed by dynamically remapping visual feature information between retinotopic regions within early visual areas. |
Wendy Ming; Dimitrios J. Palidis; Miriam Spering; Martin J. McKeown Visual contrast sensitivity in early-stage parkinson's disease Journal Article In: Investigative Ophthalmology & Visual Science, vol. 57, no. 13, pp. 5696–5704, 2016. @article{Ming2016, Purpose: Visual impairments are frequent in Parkinson's disease (PD) and impact normal functioning in daily activities. Visual contrast sensitivity is a powerful nonmotor sign for discriminating PD patients from controls. However, it is usually assessed with static visual stimuli. Here we examined the interaction between perception and eye movements in static and dynamic contrast sensitivity tasks in a cohort of mildly impaired, early-stage PD patients. Methods: Patients (n = 13) and healthy age-matched controls (n = 12) viewed stimuli of various spatial frequencies (0-8 cyc/deg) and speeds (0°/s, 10°/s, 30°/s) on a computer monitor. Detection thresholds were determined by asking participants to adjust luminance contrast until they could just barely see the stimulus. Eye position was recorded with a video-based eye tracker. Results: Patients' static contrast sensitivity was impaired in the intermediate spatial-frequency range and this impairment correlated with fixational instability. However, dynamic contrast sensitivity and patients' smooth pursuit were relatively normal. An independent component analysis revealed contrast sensitivity profiles differentiating patients and controls. Conclusions: Our study simultaneously assesses perceptual contrast sensitivity and eye movements in PD, revealing a possible link between fixational instability and perceptual deficits. Spatiotemporal contrast sensitivity profiles may represent an easily measurable metric as a component of a broader combined biometric for nonmotor features observed in PD. |
Charlotte B. Montgomery; Carrie Allison; Meng Chuan Lai; Sarah Cassidy; Peter E. Langdon; Simon Baron-Cohen Do adults with high functioning Autism or Asperger syndrome differ in empathy and emotion recognition? Journal Article In: Journal of Autism and Developmental Disorders, vol. 46, no. 6, pp. 1931–1940, 2016. @article{Montgomery2016, The present study examined whether adults with high functioning autism (HFA) showed greater difficulties in (1) their self-reported ability to empathise with others and/or (2) their ability to read mental states in others' eyes than adults with Asperger syndrome (AS). The Empathy Quotient (EQ) and ‘Reading the Mind in the Eyes' Test (Eyes Test) were compared in 43 adults with AS and 43 adults with HFA. No significant difference was observed on EQ score between groups, while adults with AS performed significantly better on the Eyes Test than those with HFA. This suggests that adults with HFA may need more support, particularly in mentalizing and complex emotion recognition, and raises questions about the existence of subgroups within autism spectrum conditions. |
Kinan Muhammed; Sanjay G. Manohar; Michael Ben Yehuda; Trevor T. J. Chong; George Tofaris; Graham Lennox; Marko Bogdanovic; Michele Hu; Masud Husain Reward sensitivity deficits modulated by dopamine are associated with apathy in Parkinson's disease Journal Article In: Brain, vol. 139, no. 10, pp. 2706–2721, 2016. @article{Muhammed2016, Apathy is a debilitating and under-recognized condition that has a significant impact in many neurodegenerative disorders. In Parkinson's disease, it is now known to contribute to worse outcomes and a reduced quality of life for patients and carers, adding to health costs and extending disease burden. However, despite its clinical importance, there remains limited understanding of mechanisms underlying apathy. Here we investigated if insensitivity to reward might be a contributory factor and examined how this relates to severity of clinical symptoms. To do this we created novel ocular measures that indexed motivation level using pupillary and saccadic response to monetary incentives, allowing reward sensitivity to be evaluated objectively. This approach was tested in 40 patients with Parkinson's disease, 31 elderly age-matched control participants and 20 young healthy volunteers. Thirty patients were examined ON and OFF their dopaminergic medication in two counterbalanced sessions, so that the effect of dopamine on reward sensitivity could be assessed. Pupillary dilation to increasing levels of monetary reward on offer provided quantifiable metrics of motivation in healthy subjects as well as patients. Moreover, pupillary reward sensitivity declined with age. In Parkinson's disease, reduced pupillary modulation by incentives was predictive of apathy severity, and independent of motor impairment and autonomic dysfunction as assessed using overnight heart rate variability measures. Reward sensitivity was further modulated by dopaminergic state, with blunted sensitivity when patients were OFF dopaminergic drugs, both in pupillary response and saccadic peak velocity response to reward. These findings suggest that reward insensitivity may be a contributory mechanism to apathy and provide potential new clinical measures for improved diagnosis and monitoring of apathy. |
Aidan P. Murphy; David A. Leopold; Glyn W. Humphreys; Andrew E. Welchman Lesions to right posterior parietal cortex impair visual depth perception from disparity but not motion cues Journal Article In: Philosophical Transactions of the Royal Society B: Biological Sciences, vol. 371, pp. 1–17, 2016. @article{Murphy2016, The posterior parietal cortex (PPC) is understood to be active when observers perceive three-dimensional (3D) structure. However, it is not clear how central this activity is in the construction of 3D spatial representations. Here, we examine whether PPC is essential for two aspects of visual depth perception by testing patients with lesions affecting this region. First, we measured subjects' ability to discriminate depth structure in various 3D surfaces and objects using binocular disparity. Patients with lesions to right PPC (N = 3) exhibited marked perceptual deficits on these tasks, whereas those with left hemisphere lesions (N = 2) were able to reliably discriminate depth as accurately as control subjects. Second, we presented an ambiguous 3D stimulus defined by structure from motion to determine whether PPC lesions influence the rate of bistable perceptual alternations. Patients' percept durations for the 3D stimulus were generally within a normal range, although the two patients with bilateral PPC lesions showed the fastest perceptual alternation rates in our sample. Intermittent stimulus presentation reduced the reversal rate similarly across subjects. Together, the results suggest that PPC plays a causal role in both inferring and maintaining the perception of 3D structure with stereopsis supported primarily by the right hemisphere, but do not lend support to the view that PPC is a critical contributor to bistable perceptual alternations. |
Tyler R. Peel; Ziad M. Hafed; Suryadeep Dash; Stephen G. Lomber; Brian D. Corneil A causal role for the cortical frontal eye fields in microsaccade deployment Journal Article In: PLoS Biology, vol. 14, no. 8, pp. e1002531, 2016. @article{Peel2016, Microsaccades aid vision by helping to strategically sample visual scenes. Despite the importance of these small eye movements, no cortical area has ever been implicated in their generation. Here, we used unilateral and bilateral reversible inactivation of the frontal eye fields (FEF) to identify a cortical drive for microsaccades. Unexpectedly, FEF inactivation altered microsaccade metrics and kinematics. Such inactivation also impaired microsaccade deployment following peripheral cue onset, regardless of cue side or inactivation configuration. Our results demonstrate that the FEF provides critical top-down drive for microsaccade generation, particularly during the recovery of microsaccades after disruption by sensory transients. Our results constitute the first direct evidence, to our knowledge, for the contribution of any cortical area to microsaccade generation, and they provide a possible substrate for how cognitive processes can influence the strategic deployment of microsaccades. |
Christina U. Pfeuffer; Andrea Kiesel; Lynn Huestegge A look into the future: Spontaneous anticipatory saccades reflect processes of anticipatory action control Journal Article In: Journal of Experimental Psychology: General, vol. 145, no. 11, pp. 1530–1547, 2016. @article{Pfeuffer2016, According to ideomotor theory, human action control uses anticipations of one's own actions' future consequences, that is, action effect anticipations, as a means of triggering actions that will produce desired outcomes (e.g., Hommel, Müsseler, Aschersleben, & Prinz, 2001). Using the response-effect compatibility paradigm (Kunde, 2001), we demonstrate that the anticipation of one's own manual actions' future consequences not only triggers appropriate (i.e., instructed) actions, but simultaneously induces spontaneous (uninstructed) anticipatory saccades to the location of future action consequences. In contrast to behavioral response-effect compatibility effects that have been linked to processes of action selection and action planning, our results suggest that these anticipatory saccades serve the function of outcome evaluation, that is, the comparison of expected/intended and observed action outcomes. Overall, our results demonstrate the informational value of additionally analyzing uninstructed behavioral components complementary to instructed responses and allow us to specify essential mechanisms of the complex interplay between the manual and oculomotor control system in goal-directed action control. |
Alessandro Piras; Milena Raffi; Michela Persiani; Monica Perazzolo; Salvatore Squatrito Effect of heading perception on microsaccade dynamics Journal Article In: Behavioural Brain Research, vol. 312, pp. 246–252, 2016. @article{Piras2016a, The present study shows the relationship between microsaccades and heading perception. Recent research demonstrates that microsaccades during fixation are necessary to overcome loss of vision due to continuous stimulation of the retinal receptors, even at the potential cost of a decrease in visual acuity. The goal of oculomotor fixational mechanisms might be not retinal stabilization, but controlled image motion adjusted to be optimal for visual processing. Thus, patterns of microsaccades may be exploited to help to understand the oculomotor system, aspects of visual perception, and the dynamics of visual attention. We presented an expansion optic flow in which the dot speed simulated a heading directed to the left or to the right of the subject, who had to signal the perceived heading by making a saccade toward the perceived direction. We recorded microsaccades during the optic flow stimulation to investigate their characteristics before and after the response. The time spent on heading perception was similar between right and left direction, and response latency was shorter during correct than incorrect responses. Furthermore, we observed that correct heading perception is associated with longer, larger and faster microsaccade characteristics. The time-course of microsaccade rate shows a modulation across the perception process similar to that seen for other local perception tasks, while the main direction is oriented toward the opposite side with respect to the perceived heading. Microsaccades enhance visual perception and, therefore, represent a fundamental motor process, with a specific effect for the build-up of global visual perception of space. |
Yuval Porat; Ehud Zohary Practice improves peri-saccadic shape judgment but does not diminish target mislocalization Journal Article In: Proceedings of the National Academy of Sciences, vol. 113, no. 46, pp. E7327–E7336, 2016. @article{Porat2016, Visual sensitivity is markedly reduced during an eye movement. Peri-saccadic vision is also characterized by a mislocalization of the briefly presented stimulus closer to the saccadic target. These features are commonly viewed as obligatory elements of peri-saccadic vision. However, practice improves performance in many perceptual tasks performed at threshold conditions. We wondered if this could also be the case with peri-saccadic perception. To test this, we used a paradigm in which subjects reported the orientation (or location) of an ellipse briefly presented during a saccade. Practice on peri-saccadic orientation discrimination led to long-lasting gains in that task but did not alter the classical mislocalization of the visual stimulus. Shape discrimination gains were largely generalized to other untrained conditions when the same stimuli were used (discrimination during a saccade in the opposite direction or at a different stimulus location than previously trained). However, performance dropped to baseline level when participants shifted to a novel Vernier discrimination task under identical saccade conditions. Furthermore, practice on the location task did not induce better stimulus localization or discrimination. These results suggest that the limited visual information available during a saccade may be better used with practice, possibly by focusing attention on the specific target features or a better readout of the available information. Saccadic mislocalization, by contrast, is robust and resistant to top-down modulations, suggesting that it involves an automatic process triggered by the upcoming execution of a saccade (e.g., an efference copy signal). |
Maria Solé Puig; Josep Marco Pallarés; Laura Perez Zapata; Laura Puigcerver; Josep Cañete; Hans Supèr Attentional selection accompanied by eye vergence as revealed by event-related brain potentials Journal Article In: PLoS ONE, vol. 11, no. 12, pp. e0167646, 2016. @article{Puig2016, Neural mechanisms of attention allow selective sensory information processing. Top-down deployment of visual-spatial attention is conveyed by cortical feedback connections from frontal regions to lower sensory areas modulating late stimulus responses. A recent study reported the occurrence of small eye vergence during orienting top-down attention. Here we assessed a possible link between vergence and attention by comparing visual event related potentials (vERPs) to a cue stimulus that induced attention to shift towards the target location to the vERPs to a no-cue stimulus that did not trigger orienting attention. The results replicate the findings of eye vergence responses during orienting attention and show that the strength and time of eye vergence coincide with the onset and strength of the vERPs when subjects oriented attention. Our findings therefore support the idea that eye vergence relates to and possibly has a role in attentional selection. |
Maria M. Robinson; David E. Irwin Shifts of attention bias awareness of voluntary and reflexive eye movements Journal Article In: Experimental Brain Research, vol. 234, no. 6, pp. 1689–1699, 2016. @article{Robinson2016, Current theories regarding factors that influence people's awareness of their actions have underscored the role of peripheral signals (e.g., proprioceptive feedback) and central commands (e.g., the intention to make a response). The role of covert attention has been largely underexplored, even though attention and awareness have been tightly linked. The aim of the current study was to directly examine the impact of shifts of visual attention on people's awareness of their eye movements as they performed the antisaccade task. People tend to be unaware of a high percentage of erroneous eye movements on this task, thus lending it to the study of variables that might modulate people's awareness of their actions. In addition, this task provides the opportunity to compare two classes of actions, voluntary (antisaccade) and involuntary (erroneous prosaccade) eye movements, and thus to assess whether shifts of covert attention can or cannot override sources of information that may be present when people make voluntary but not reflexive responses. We found that shifts of visual attention did indeed influence participants' awareness of their own eye movements, leading them to misperceive reflexive and voluntary movements alike, suggesting that covert attention may override both peripheral and central signals to bias awareness. |
Lars O. M. Rothkegel; Hans A. Trukenbrod; Heiko H. Schütt; Felix A. Wichmann; Ralf Engbert Influence of initial fixation position in scene viewing Journal Article In: Vision Research, vol. 129, pp. 33–49, 2016. @article{Rothkegel2016a, During scene perception our eyes generate complex sequences of fixations. Predictors of fixation locations are bottom-up factors such as luminance contrast, top-down factors like viewing instruction, and systematic biases, e.g., the tendency to place fixations near the center of an image. However, comparatively little is known about the dynamics of scanpaths after experimental manipulation of specific fixation locations. Here we investigate the influence of initial fixation position on subsequent eye-movement behavior on an image. We presented 64 colored photographs to participants who started their scanpaths from one of two experimentally controlled positions in the right or left part of an image. Additionally, we used computational models to predict the images' fixation locations and classified them as balanced images or images with high conspicuity on either the left or right side of a picture. The manipulation of the starting position influenced viewing behavior for several seconds and produced a tendency to overshoot to the image side opposite to the starting position. Possible mechanisms for the generation of this overshoot were investigated using numerical simulations of statistical and dynamical models. Our model comparisons show that inhibitory tagging is a viable mechanism for dynamical planning of scanpaths. |
2015 |
Hayley Crawford; Joanna Moss; Giles M. Anderson; Chris Oliver; Joseph P. McCleery Implicit discrimination of basic facial expressions of positive/negative emotion in Fragile X syndrome and autism spectrum disorder Journal Article In: American Journal on Intellectual and Developmental Disabilities, vol. 120, no. 4, pp. 328–345, 2015. @article{Crawford2015, Fragile X syndrome (FXS) and autism spectrum disorders (ASD) are characterized by impaired social functioning. We examined the spontaneous discrimination of happy and disgusted facial expressions, from neutral faces, in individuals with FXS (n = 13 |
Yuka Matsuo; Masayuki Watanabe; Masako Taniike; Ikuko Mohri; Syoji Kobashi; Masaya Tachibana; Yasushi Kobayashi; Yuri Kitamura Kitamura Gap effect abnormalities during a visually guided pro-saccade task in children with attention deficit hyperactivity disorder Journal Article In: PLoS ONE, vol. 10, no. 5, pp. e0125573, 2015. @article{Matsuo2015, Attention deficit hyperactivity disorder (ADHD) is a neurodevelopmental disorder that starts in early childhood and has a comprehensive impact on psychosocial activity and education as well as general health across the lifespan. Despite its prevalence, the current diagnostic criteria for ADHD are debated. Saccadic eye movements are easy to quantify and may be a quantitative biomarker for a wide variety of neurological and psychiatric disorders, including ADHD. The goal of this study was to examine whether children with ADHD exhibit abnormalities during a visually guided pro-saccadic eye-movement and to clarify the neurophysiological mechanisms associated with their behavioral impairments. Thirty-seven children with ADHD (aged 5–11 years) and 88 typically developing (TD) children (aged 5–11 years) were asked to perform a simple saccadic eye-movement task in which step and gap conditions were randomly interleaved. We evaluated the gap effect, which is the difference in the reaction time between the two conditions. Children with ADHD had a significantly longer reaction time than TD children (p < 0.01) and the gap effect was markedly attenuated (p < 0.01). These results suggest that the measurement of saccadic eye movements may provide a novel method for evaluating the behavioral symptoms and clinical features of ADHD, and that the gap effect is a potential biomarker for the diagnosis of ADHD in early childhood. |
Sören Krach; Inge Kamp-Becker; Wolfgang Einhäuser; Jens Sommer; Stefan Frässle; Andreas Jansen; Lena Rademacher; Laura Müller-Pinzler; Valeria Gazzola; Frieder M. Paulus Evidence from pupillometry and fMRI indicates reduced neural response during vicarious social pain but not physical pain in autism Journal Article In: Human Brain Mapping, vol. 36, no. 11, pp. 4730–4744, 2015. @article{Krach2015, Autism spectrum disorder (ASD) is characterized by substantial social deficits. The notion that dysfunctions in neural circuits involved in sharing another's affect explain these deficits is appealing, but has received only modest experimental support. Here we evaluated a complex paradigm on the vicarious social pain of embarrassment to probe social deficits in ASD as to whether it is more potent than paradigms currently in use. To do so we acquired pupillometry and fMRI in young adults with ASD and matched healthy controls. During a simple vicarious physical pain task no differences emerged between groups in behavior, pupillometry, and neural activation of the anterior insula (AIC) and anterior cingulate cortex (ACC). In contrast, processing complex vicarious social pain yielded reduced responses in ASD on all physiological measures of sharing another's affect. The reduced activity within the AIC was thereby explained by the severity of autistic symptoms in the social and affective domain. Additionally, behavioral responses lacked correspondence with the anterior cingulate and anterior insula cortex activity found in controls. Instead, behavioral responses in ASD were associated with hippocampal activity. The observed dissociation echoes the clinical observations that deficits in ASD are most pronounced in complex social situations and simple tasks may not probe the dysfunctions in neural pathways involved in sharing affect. Our results are highly relevant because individuals with ASD may have preserved abilities to share another's physical pain but still have problems with the vicarious representation of more complex emotions that matter in life. |
Jiyeon Lee; Cynthia K. Thompson Phonological facilitation effects on naming latencies and viewing times during noun and verb naming in agrammatic and anomic aphasia Journal Article In: Aphasiology, vol. 29, no. 10, pp. 1164–1188, 2015. @article{Lee2015, Background: Phonological priming has been shown to facilitate naming in$backslash$nindividuals with aphasia, as well as healthy speakers, resulting in$backslash$nfaster naming latencies. However, the mechanisms of phonological$backslash$nfacilitation (PF) in aphasia remain unclear.Aims: Within discrete vs.$backslash$ninteractive models of lexical access, this study examined whether PF$backslash$noccurs via the sub-lexical or lexical route during noun and verb naming$backslash$nin agrammatic and anomic aphasia.Methods & Procedures: Thirteen$backslash$nparticipants with agrammatic aphasia and 10 participants with anomic$backslash$naphasia and their young and age-matched controls (n=20/each) were$backslash$ntested. Experiment 1 examined noun and verb naming deficit patterns in$backslash$nan off-line confrontation naming task. Experiment 2 examined PF effects$backslash$non naming both word categories using eyetracking priming$backslash$nparadigm.Outcomes &Results: Results of Experiment 1 showed greater$backslash$nnaming difficulty for verbs than for nouns in the agrammatic group, with$backslash$nno difference between the two word categories in the anomic group. For$backslash$nboth participant groups, errors were dominated by semantic paraphasias,$backslash$nindicating impaired lexical selection. In the phonological priming task$backslash$n(Experiment 2), young and age-matched control groups showed PF in both$backslash$nnoun and verb naming. Interestingly, the agrammatic group showed PF when$backslash$nnaming verbs, but not nouns, whereas the anomic group showed PF for$backslash$nnouns only.Conclusions: Consistent with lexically mediated PF in$backslash$ninteractive models of lexical access, selective PF for different word$backslash$ncategories in our agrammatic and anomic groups suggest that phonological$backslash$nprimes facilitate lexical selection via feedback activation, resulting$backslash$nin greater PF for more difficult (i.e., verbs in agrammatic and possibly$backslash$nnouns in anomic group) lexical items. |
Rebekka Lencer; Andreas Sprenger; James L. Reilly; Jennifer E. McDowell; Leah H. Rubin; Judith A. Badner; Matcheri S. Keshavan; Godfrey D. Pearlson; Carol A. Tamminga; Elliot S. Gershon; Brett A. Clementz; John A. Sweeney Pursuit eye movements as an intermediate phenotype across psychotic disorders: Evidence from the B-SNIP study Journal Article In: Schizophrenia Research, vol. 169, no. 1-3, pp. 326–333, 2015. @article{Lencer2015, Smooth pursuit eye tracking deficits are a promising intermediate phenotype for schizophrenia and possibly for psychotic disorders more broadly. The Bipolar-Schizophrenia Network on Intermediate Phenotypes (B-SNIP) consortium investigated the severity and familiality of different pursuit parameters across psychotic disorders. Probands with schizophrenia (N=265), schizoaffective disorder (N=178), psychotic bipolar disorder (N=231), their first-degree relatives (N=306 |
Xiaowei Li; Bin Hu; Tingting Xu; Ji Shen; Martyn Ratcliffe A study on EEG-based brain electrical source of mild depressed subjects Journal Article In: Computer Methods and Programs in Biomedicine, vol. 120, no. 3, pp. 135–141, 2015. @article{Li2015a, Background and objective: Several abnormal brain regions are known to be linked to depression, including amygdala, orbitofrontal cortex (OFC), anterior cingulate cortex (ACC), and dorsolateral prefrontal cortex (DLPFC) etc. The aim of this study is to apply EEG (electroencephalogram) data analysis to investigate, with respect to mild depression, whether there exists dysregulation in these brain regions. Methods: EEG sources were assessed from 9 healthy and 9 mildly depressed subjects who were classified according to the Beck Depression Inventory (BDI) criteria. t-Test was used to calculate the eye movement data and standardized low resolution tomography (sLORETA) was used to correlate EEG activity. Results: A comparison of eye movement data between the healthy and mild depressed subjects exhibited that mildly depressed subjects spent more time viewing negative emotional faces. Comparison of the EEG from the two groups indicated higher theta activity in BA6 (Brodmann area) and higher alpha activity in BA38. Conclusions: EEG source location results suggested that temporal pole activity to be dysregulated, and eye-movement data analysis exhibited mild depressed subjects paid much more attention to negative face expressions, which is also in accordance with the results of EEG source location. |
Shunichi Matsuda; Hideyuki Matsumoto; Toshiaki Furubayashi; Hideki Fukuda; Ritsuko Hanajima; Shoji Tsuji; Yoshikazu Ugawa; Yasuo Terao Visual scanning area is abnormally enlarged in hereditary pure Cerebellar ataxia Journal Article In: Cerebellum, vol. 14, no. 2, pp. 63–71, 2015. @article{Matsuda2015, The aim of paper was to investigate abnormalities in visual scanning using an eye-tracking device with patients with spinocerebellar ataxia type 6 (SCA6) and SCA31, pure cerebellar types of spinocerebellar degeneration. Nineteen SCA patients (12 patients with SCA6 and 7 patients with SCA31) and 19 normal subjects in total participated in the study. While the subjects viewed images of varying complexity for later recall, we compared the visual scanning parameters between SCA patients and normal subjects. SCA patients had lower image recall scores. The scanned area in SCA patients was consistently larger than that in normal subjects. The amplitude of saccades was slightly larger in SCA patients than that in normal subjects, although it did not statistically differ between the two groups and correlated significantly with the scanned area in most images in SCA patients. The instability ratio of fixation, reflecting gaze-evoked nystagmus and downbeat nystagmus, was higher in SCA patients than that in normal subjects. Since SCA patients showed low scores despite wide visual scanning, the scanned area is considered to be abnormally enlarged. The larger scanned area in SCA patients was supposed mainly to result from the slightly larger saccade amplitude. Additionally, SCA patients showed prominent fixation disturbances probably due to gaze-evoked nystagmus and downbeat nystagmus. Consequently, SCA patients suffer from recognizing various objects in daily life, probably due to the impaired saccade control and impaired fixation. |
Phillip D. Fletcher; Jennifer M. Nicholas; Timothy J. Shakespeare; Laura E. Downey; Hannah L. Golden; Jennifer L. Agustus; Camilla N. Clark; Catherine J. Mummery; Jonathan M. Schott; Sebastian J. Crutch; Jason D. Warren Dementias show differential physiological responses to salient sounds Journal Article In: Frontiers in Behavioral Neuroscience, vol. 9, pp. 73, 2015. @article{Fletcher2015, Abnormal responsiveness to salient sensory signals is often a prominent feature of dementia diseases, particularly the frontotemporal lobar degenerations, but has been little studied. Here we assessed processing of one important class of salient signals, looming sounds, in canonical dementia syndromes. We manipulated tones using intensity cues to create percepts of salient approaching ("looming") or less salient withdrawing sounds. Pupil dilatation responses and behavioral rating responses to these stimuli were compared in patients fulfilling consensus criteria for dementia syndromes (semantic dementia |
John J. Foxe; Sophie Molholm; Victor A. Del Bene; Hans Peter Frey; Natalie N. Russo; Daniella Blanco; Dave Saint-Amour; Lars A. Ross In: Cerebral Cortex, vol. 25, no. 2, pp. 298–312, 2015. @article{Foxe2015, Under noisy listening conditions, visualizing a speaker's articulations substantially improves speech intelligibility. This multisensory speech integration ability is crucial to effective communication, and the appropriate development of this capacity greatly impacts a child's ability to successfully navigate educational and social settings. Research shows that multisensory integration abilities continue developing late into childhood. The primary aim here was to track the development of these abilities in children with autism, since multisensory deficits are increasingly recognized as a component of the autism spectrum disorder (ASD) phenotype. The abilities of high-functioning ASD children (n = 84) to integrate seen and heard speech were assessed cross-sectionally, while environmental noise levels were systematically manipulated, comparing them with age-matched neurotypical children (n = 142). Severe integration deficits were uncovered in ASD, which were increasingly pronounced as background noise increased. These deficits were evident in school-aged ASD children (5–12 year olds), but were fully ameliorated in ASD children entering adolescence (13–15 year olds). The severity of multisensory deficits uncovered has important implications for educators and clinicians working in ASD. We consider the observation that the multisensory speech system recovers substantially in adolescence as an indication that it is likely amenable to intervention during earlier childhood, with potentially profound implications for the development of social communication abilities in ASD children. |
Franziska Geringswald; Anne Herbik; Wolfram Hofmüller; Michael B. Hoffmann; Stefan Pollmann Visual memory for objects following foveal vision loss Journal Article In: Journal of Experimental Psychology: Learning, Memory, and Cognition, vol. 41, no. 5, pp. 1471–1484, 2015. @article{Geringswald2015a, Allocation of visual attention is crucial for encoding items into visual long-term memory. In free vision, attention is closely linked to the center of gaze, raising the question whether foveal vision loss entails suboptimal deployment of attention and subsequent impairment of object encoding. To investigate this question, we examined visual long-term memory for objects in patients suffering from foveal vision loss due to age-related macular degeneration. We measured patients' change detection sensitivity after a period of free scene exploration monocularly with their worse eye when possible, and under binocular vision, comparing sensitivity and eye movements to matched normal-sighted controls. A highly salient cue was used to capture attention to a nontarget location before a target change occurred in half of the trials, ensuring that change detection relied on memory. Patients' monocular and binocular sensitivity to object change was comparable to controls, even after more than 4 intervening fixations, and not significantly correlated with visual impairment. We conclude that extrafoveal vision suffices for efficient encoding into visual long-term memory. |
Alma Gharib; Daniela Mier; Ralph Adolphs; Shinsuke Shimojo Eyetracking of social preference choices reveals normal but faster processing in autism Journal Article In: Neuropsychologia, vol. 72, pp. 70–79, 2015. @article{Gharib2015, People with Autism Spectrum Disorder (ASD) have been reported to show atypical attention and evaluative processing, in particular for social stimuli such as faces. The usual measure in these studies is an explicit, subjective judgment, which is the culmination of complex-temporally extended processes that are not typically dissected in detail. Here we addressed a neglected aspect of social decision-making in order to gain further insight into the underlying mechanisms: the temporal evolution of the choice. We investigated this issue by quantifying the alternating patterns of gaze onto faces, as well as nonsocial stimuli, while subjects had to decide which of the two stimuli they preferred. Surprisingly, the temporal profile of fixations relating to choice (the so-called "gaze cascade") was entirely normal in ASD, as were the eventual preference choices. Despite these similarities, we found two key abnormalities: people with ASD made choices more rapidly than did control subjects across the board, and their reaction times for social preference judgments were insensitive to choice difficulty. We suggest that ASD features an altered decision-making process when basing choice on social preferences. One hypothesis motivated by these data is that a choice criterion is reached in ASD regardless of the discriminability of the options. |
Fatema F. Ghasia; Aasef G. Shaikh Head oscillations in infantile nystagmus syndrome Journal Article In: Journal of AAPOS, vol. 19, no. 1, pp. 38–41, 2015. @article{Ghasia2015, PURPOSE: To quantitatively characterize eye and head oscillations in patients with infantile nystagmus syndrome (INS). METHODS: Vertical and horizontal eye and head position in INS patients were measured simultaneously at a sampling frequency of 500 Hz. Eye and head movements were measured continuously for 180 seconds. The data was calibrated and converted to angular vectors, which were further analyzed with custom software. RESULTS: A total of 10 patients with INS were included: 3 with pseudo-jerk, 3 with pure-jerk, 2 with pseudo-pendular with foveating saccade form of jerk, 1 with bidirectional jerk, and 1 with asymmetric pendular nystagmus waveforms. None of the patients had periodic, aperiodic, or a superimposed latent nystagmus component. Two types of head oscillations were observed: one with a frequency of 1-3 Hz, present in all patients; and another with a frequency range of 5-8 Hz, present in only 7 patients. High-frequency oscillations were episodic, whereas low-frequency oscillations were constantly present. Peak velocity of the high-frequency head oscillations and eye velocity of nystagmus were not correlated, suggesting that these oscillations did not influence foveation. CONCLUSIONS: Two types of head oscillations were found in INS patients: a constant, low-frequency and an episodic, high-frequency. Lack of correlation between the foveation period of nystagmus and peak head velocity during high-frequency oscillations suggests a coexisting pathological phenomenon rather than a compensatory mechanism used to improve the visual acuity. |
Fatema F. Ghasia; Aasef G. Shaikh; Jonathan B. Jacobs; Mark F. Walker Cross-coupled eye movement supports neural origin of pattern strabismus Journal Article In: Investigative Ophthalmology & Visual Science, vol. 56, no. 5, pp. 2855–2866, 2015. @article{Ghasia2015b, PURPOSE: Pattern strabismus describes vertically incomitant horizontal strabismus. Conventional theories emphasized the role of orbital etiologies, such as abnormal fundus torsion and misaligned orbital pulleys as a cause of the pattern strabismus. Experiments in animal models, however, suggested the role of abnormal cross-connections between the neural circuits. We quantitatively assessed eye movements in patients with pattern strabismus with a goal to delineate the role of neural circuits versus orbital etiologies.$backslash$n$backslash$nMETHODS: We measured saccadic eye movements with high-precision video-oculography in 14 subjects with pattern strabismus, 5 with comitant strabismus, and 15 healthy controls. We assessed change in eye position in the direction orthogonal to that of the desired eye movement (cross-coupled responses). We used fundus photography to quantify the fundus torsion.$backslash$n$backslash$nRESULTS: We found cross-coupling of saccades in all patients with pattern strabismus. The cross-coupled responses were in the same direction in both eyes, but larger in the nonviewing eye. All patients had clinically apparent inferior oblique overaction with abnormal excylotorsion. There was no correlation between the amount of the fundus torsion or the grade of oblique overaction and the severity of cross-coupling. The disconjugacy in the saccade direction and amplitude in pattern strabismics did not have characteristics predicted by clinically apparent inferior oblique overaction.$backslash$n$backslash$nCONCLUSIONS: Our results validated primate models of pattern strabismus in human patients. We found no correlation between ocular torsion or oblique overaction and cross-coupling. Therefore, we could not ascribe cross-coupling exclusively to the orbital etiology. Patients with pattern strabismus could have abnormalities in the saccade generators. |
Bruno Gingras; Manuela M. Marin; Estela Puig-Waldmüller; W. T. Fitch The eye is listening: Music-induced arousal and Iindividual differences predict pupillary responses Journal Article In: Frontiers in Human Neuroscience, vol. 9, pp. 619, 2015. @article{Gingras2015, Pupillary responses are a well-known indicator of emotional arousal but have not yet been systematically investigated in response to music. Here, we measured pupillary dilations evoked by short musical excerpts normalized for intensity and selected for their stylistic uniformity. Thirty participants (15 females) provided subjective ratings of music-induced felt arousal, tension, pleasantness, and familiarity for 80 classical music excerpts. The pupillary responses evoked by these excerpts were measured in another thirty participants (15 females). We probed the role of listener-specific characteristics such as mood, stress reactivity, self-reported role of music in life, liking for the selected excerpts, as well as of subjective responses to music, in pupillary responses. Linear mixed model analyses showed that a greater role of music in life was associated with larger dilations, and that larger dilations were also predicted for excerpts rated as more arousing or tense. However, an interaction between arousal and liking for the excerpts suggested that pupillary responses were modulated less strongly by arousal when the excerpts were particularly liked. An analogous interaction was observed between tension and liking. Additionally, males exhibited larger dilations than females. Overall, these findings suggest a complex interplay between bottom-up and top-down influences on pupillary responses to music. |
Shahrbanoo Hamel; Dominique Houzet; Denis Pellerin; Nathalie Guyader Does color influence eye movements while exploring videos? Journal Article In: Journal of Eye Movement Research, vol. 8, no. 1, pp. 1–10, 2015. @article{Hamel2015, Although visual attention studies consider color as one of the most important features in guiding visual attention, few studies have investigated how color influences eye movements while viewing natural scenes without any particular task. To better understand the visual features that drive attention, the aim of this paper was to quantify the influence of color on eye movements when viewing dynamic natural scenes. The influence of color was investigated by comparing the eye positions of several observers eye-tracked while viewing video stimuli in two conditions: color and grayscale. The comparison was made using the dispersion between the eye positions of observers, the number of attractive regions measured with a clustering method applied to the eye positions, and by comparing eye positions to the predictions of a saliency model. The mean amplitude of saccades and the mean duration of fixations were compared as well. Globally, a slight influence of color on eye movements was measured; only the number of attractive regions for color stimuli was slightly higher than for grayscale stimuli. However, a luminance-based saliency model predicts the eye positions for color stimuli as efficiently as for grayscale stimuli. |
James J. Harrison; Petroc Sumner; Matt J. Dunn; Jonathan T. Erichsen; Tom C. A. Freeman Quick phases of infantile nystagmus show the saccadic inhibition effect Journal Article In: Investigative Ophthalmology & Visual Science, vol. 56, no. 3, pp. 1594–1600, 2015. @article{Harrison2015, PURPOSE: Infantile nystagmus (IN) is a pathological, involuntary oscillation of the eyes consisting of slow, drifting eye movements interspersed with rapid reorienting quick phases. The extent to which quick phases of IN are programmed similarly to saccadic eye movements remains unknown. We investigated whether IN quick phases exhibit 'saccadic inhibition,' a phenomenon typically related to normal targeting saccades, in which the initiation of the eye movement is systematically delayed by task-irrelevant visual distractors. METHODS: We recorded eye position from 10 observers with early-onset idiopathic nystagmus while task-irrelevant distractor stimuli were flashed along the top and bottom of a large screen at ±10° eccentricity. The latency distributions of quick phases were measured with respect to these distractor flashes. Two additional participants, one with possible albinism and one with fusion maldevelopment nystagmus syndrome, were also tested. RESULTS: All observers showed that a distractor flash delayed the execution of quick phases that would otherwise have occurred approximately 100 ms later, exactly as in the standard saccadic inhibition effect. The delay did not appear to differ between the two main nystagmus types under investigation (idiopathic IN with unidirectional and bidirectional jerk). CONCLUSIONS: The presence of the saccadic inhibition effect in IN quick phases is consistent with the idea that quick phases and saccades share a common programming pathway. This could allow quick phases to take on flexible, goal-directed behavior, at odds with the view that IN quick phases are stereotyped, involuntary eye movements. |
Christoph Helmchen; Evripides Livitzis; Andreas Sprenger; Peter Trillenberg Cerebellar ataxia with unilateral high frequency vestibulopathy and caloric disinhibition Journal Article In: Journal of the Neurological Sciences, vol. 358, no. 1-2, pp. 527–529, 2015. @article{Helmchen2015, Quantitative analysis of the head impulse test (qHIT), known as the Halmagyi–Curthoys test, has recently more commonly been used in standard diagnostic work up of patients with dizziness, due to modern videooculography systems. qHIT examines the high frequency, high acceleration components of the vestibulo-ocular reflex (VOR), in contrast to caloric irrigation which tests its low frequency components. Here we present a patient with a unilateral vestibulopathy during qHIT suspected to suffer from peripheral unilateral vestibulopathy who showed profoundly increased caloric responses on the lesion side. We provide some evidence that this probably indicates cerebellar disease. |
Richard W. Hertle; Dongsheng Yang; Tonia Adkinson; Michael Reed Topical brinzolamide (Azopt) versus placebo in the treatment of infantile nystagmus syndrome (INS) Journal Article In: British Journal of Ophthalmology, vol. 99, no. 4, pp. 471–476, 2015. @article{Hertle2015, PURPOSE:To test the hypothesis that the topical carbonic anhydrase inhibitor brinzolamide (Azopt) has beneficial effects versus placebo on measures of nystagmus and visual acuity in adult subjects with infantile nystagmus syndrome (INS). DESIGN:Prospective, cross-over, double masked clinical trial. METHODS: SETTING:Single centre. STUDY POPULATION:Five subjects ≥18 years old with typical INS and best-binocular visual acuity in their primary position null zone ETDRS 55 letters to 85 letters (20/200 to 20/50) and had no previous treatment for nystagmus. INTERVENTION:In a randomised order, each subject received one drop of Azopt or placebo in both eyes three times a day separated by a washout period of at least a week followed by Azopt or placebo in both eyes three times a day; thus each subject got the drug and placebo, each acting as his or her own control. OUTCOME MEASURES:The nystagmus acuity function and INS waveforms obtained from eye movement recordings, binocular optotype visual acuity, using the ETDRS protocol analysed individually and as a group before and after Azopt and placebo. RESULTS:Versus placebo and baseline measures, topical Azopt significantly improved; INS waveform characteristics in the primary position null zone, group mean values of the nystagmus acuity function across gaze (p<0.01) and group mean ETDRS binocular letter visual acuity (p<0.05). There was a predictable decrease in intraocular pressure (IOP) without any systemic or ocular adverse events. CONCLUSIONS:Although a prospective large-scale clinical trial is needed to prove effectiveness, an eye-drop-based therapy for INS may emerge as a viable addition to optical, surgical, behavioural and systemic drug therapies for INS. |
Angelina Paolozza; Rebecca Munn; Douglas P. Munoz; James N. Reynolds Eye movements reveal sexually dimorphic deficits in children with fetal alcohol spectrum disorder Journal Article In: Frontiers in Neuroscience, vol. 9, pp. 76, 2015. @article{Paolozza2015, BACKGROUND: We examined the accuracy and characteristics of saccadic eye movements in children with fetal alcohol spectrum disorder (FASD) compared with typically developing control children. Previous studies have found that children with FASD produce saccades that are quantifiably different from controls. Additionally, animal studies have found sex-based differences for behavioral effects after prenatal alcohol exposure. Therefore, we hypothesized that eye movement measures will show sexually dimorphic results. METHODS: Children (aged 5-18 years) with FASD (n = 71) and typically developing controls (n = 113) performed a visually-guided saccade task. Saccade metrics and behavior were analyzed for sex and group differences. RESULTS: Female control participants had greater amplitude saccades than control males or females with FASD. Accuracy was significantly poorer in the FASD group, especially in males, which introduced significantly greater variability in the data. Therefore, we conducted additional analyses including only those trials in which the first saccade successfully reached the target within a ± 1° window. In this restricted amplitude dataset, the females with FASD made saccades with significantly lower velocity and longer duration, whereas the males with FASD did not differ from the control group. Additionally, the mean and peak deceleration were selectively decreased in the females with FASD. CONCLUSIONS: These data support the hypothesis that children with FASD exhibit specific deficits in eye movement control and sensory-motor integration associated with cerebellar and/or brain stem circuits. Moreover, prenatal alcohol exposure may have a sexually dimorphic impact on eye movement metrics, with males and females exhibiting differential patterns of deficit. |
Frieder M. Paulus; Sören Krach; Marius Blanke; Christine Roth; Marcus Belke; Jens Sommer; Laura Müller-Pinzler; Katja Menzler; Andreas Jansen; Felix Rosenow; Frank Bremmer; Wolfgang Einhäuser; Susanne Knake Fronto-insula network activity explains emotional dysfunctions in juvenile myoclonic epilepsy: Combined evidence from pupillometry and fMRI Journal Article In: Cortex, vol. 65, pp. 219–231, 2015. @article{Paulus2015, Emotional instability, difficulties in social adjustment, and disinhibited behavior are the most common symptoms of the psychiatric comorbidities in juvenile myoclonic epilepsy (JME). This psychopathology has been associated with dysfunctions of mesial-frontal brain circuits. The present work is a first direct test of this link and adapted a paradigm for probing frontal circuits during empathy for pain. Neural and psychophysiological parameters of pain empathy were assessed by combining functional magnetic resonance imaging (fMRI) with simultaneous pupillometry in 15 JME patients and 15 matched healthy controls. In JME patients, we observed reduced neural activation of the anterior cingulate cortex (ACC), the anterior insula (AI), and the ventrolateral prefrontal cortex (VLPFC). This modulation was paralleled by reduced pupil dilation during empathy for pain in patients. At the same time, pupil dilation was positively related to neural activity of the ACC, AI, and VLPFC. In JME patients, the ACC additionally showed reduced functional connectivity with the primary and secondary somatosensory cortex, areas fundamentally implicated in processing the somatic cause of another's pain. Our results provide first evidence that alterations of mesial-frontal circuits directly affect psychosocial functioning in JME patients and draw a link of pupil dynamics with brain activity during emotional processing. The findings of reduced pain empathy related activation of the ACC and AI and aberrant functional integration of the ACC with somatosensory cortex areas provide further evidence for this network's role in social behavior and helps explaining the JME psychopathology and patients' difficulties in social adjustment. |
Manuel Perea; María Jiménez; Miguel Martín-Suesta; Pablo Gómez Letter position coding across modalities: Braille and sighted reading of sentences with jumbled words Journal Article In: Psychonomic Bulletin & Review, vol. 22, no. 2, pp. 531–536, 2015. @article{Perea2015, This article explores how letter position coding is attained during braille reading and its implications for models of word recognition. When text is presented visually, the reading process easily adjusts to the jumbling of some letters (jugde-judge), with a small cost in reading speed. Two explanations have been proposed: One relies on a general mechanism of perceptual uncertainty at the visual level, and the other focuses on the activation of an abstract level of representation (i.e., bigrams) that is shared by all orthographic codes. Thus, these explanations make differential predictions about reading in a tactile modality. In the present study, congenitally blind readers read sentences presented on a braille display that tracked the finger position. The sentences either were intact or involved letter transpositions. A parallel experiment was conducted in the visual modality. Results revealed a substantially greater reading cost for the sentences with transposed-letter words in braille readers. In contrast with the findings with sighted readers, in which there is a cost of transpositions in the external (initial and final) letters, the reading cost in braille readers occurs serially, with a large cost for initial letter transpositions. Thus, these data suggest that the letter-position-related effects in visual word recognition are due to the characteristics of the visual stream. |
Andrea Phillipou; Larry Allen Abel; David J. Castle; Matthew E. Hughes; Caroline T. Gurvich; Richard G. Nibbs; Susan Lee Rossell Self perception and facial emotion perception of others in anorexia nervosa Journal Article In: Frontiers in Psychology, vol. 6, pp. 1181, 2015. @article{Phillipou2015, BACKGROUND: Whether individuals with anorexia nervosa (AN) are able to accurately perceive emotions from faces of others is unclear. Furthermore, whether individuals with AN process images of their own face differently to healthy individuals has thus far not been investigated. Therefore, the aim of this study was to investigate facial affect processing and the processing of one's own face through measures of emotion identification, functional magnetic resonance imaging (fMRI) and eyetracking. METHODS: Twenty-four females with AN and 25 matched healthy control participants were presented with an implicit emotion processing task during fMRI and eyetracking, followed by an explicit emotion identification task. RESULTS: The AN group were found to 'hyperscan' stimuli and avoided visually attending to salient features of their own face images. RESULTS of the fMRI revealed increased activity to own face stimuli in AN in the right inferior and middle temporal gyri, and right lingual gyrus. AN participants were not found to display emotion identification deficits to the standard emotional face stimuli. DISCUSSION: The findings are discussed in terms of increased anxiety to disorder-relevant stimuli in AN. Potential clinical implications are discussed in relation to the use of eyetracking techniques to improve the perception of self in AN. |
Marianne E. F. Piano; Peter J. Bex; Anita J. Simmers Perceptual visual distortions in adult amblyopia and their relationship to clinical features Journal Article In: Investigative Ophthalmology & Visual Science, vol. 56, no. 9, pp. 5533–5542, 2015. @article{Piano2015, PURPOSE: Develop a paradigm to map binocular perceptual visual distortions in adult amblyopes and visually normal controls, measure their stability over time, and determine the relationship between strength of binocular single vision and distortion magnitude. METHODS: Perceptual visual distortions were measured in 24 strabismic, anisometropic, or microtropic amblyopes (interocular acuity difference ≥ 0.200 logMAR or history of amblyopia treatment) and 10 controls (mean age 27.13 ± 10.20 years). The task was mouse-based target alignment on a stereoscopic liquid crystal display monitor, measured binocularly five times during viewing dichoptically through active shutter glasses, amblyopic eye viewing cross-hairs, fellow eye viewing single target dots (16 locations within central 5°), and five times nondichoptically, with all stimuli visible to either eye. Measurements were repeated over time (1 week, 1 month) in eight amblyopic subjects, evaluating test-retest reliability. Measurements were also correlated against logMAR visual acuity, horizontal prism motor fusion range, Frisby/Preschool Randot stereoacuity, and heterophoria/heterotropia prism cover test measurement. RESULTS: Sixty-seven percent (16/24) of amblyopes had significant perceptual visual distortions under dichoptic viewing conditions compared to nondichoptic viewing conditions and dichoptic control group performance. Distortions correlated with the strength of motor fusion (r = -0.417 |
Anastasia Pilat; Daniel Sibley; Rebecca J. McLean; Frank A. Proudlock; Irene Gottlob High-resolution imaging of the optic nerve and retina in optic nerve hypoplasia Journal Article In: Ophthalmology, vol. 122, no. 7, pp. 1330–1339, 2015. @article{Pilat2015, Purpose To investigate the optic nerve and macular morphology in patients with optic nerve hypoplasia (ONH) using spectral-domain optical coherence tomography (SD OCT). Design Prospective, cross-sectional, observational study. Subjects A total of 16 participants with ONH (10 female and 6 male; mean age, 17.2 years; 6 bilateral involvement) and 32 gender-, age-, ethnicity-, and refraction-matched healthy controls. Methods High-resolution SD OCT (Copernicus [Optopol Technology S.A., Zawiercie, Poland], 3 μm resolution) and handheld SD OCT (Bioptigen Inc [Research Triangle Park, NC], 2.6 μm resolution) devices were used to acquire horizontal scans through the center of the optic disc and macula. Main Outcome Measures Horizontal optic disc/cup and rim diameters, cup depth, peripapillary retinal nerve fiber layer (RNFL), and thickness of individual retinal layers in participants with ONH and in controls. Results Patients with ONH had significantly smaller discs (P < 0.03 and P < 0.001 compared with unaffected eye and healthy controls, respectively), horizontal cup diameter (P < 0.02 for both), and cup depth (P < 0.02 and P < 0.01, respectively). In the macula, significantly thinner RNFL (nasally), ganglion cell layer (GCL) (nasally and temporally), inner plexiform layer (IPL) (nasally), outer nuclear layer (ONL) (nasally), and inner segment (centrally and temporally) were found in patients with ONH compared with the control group (P < 0.05 for all comparisons). Continuation of significantly thicker GCL, IPL, and outer plexiform layer in the central retinal area (i.e., foveal hypoplasia) was found in more than 80% of patients with ONH. Clinically unaffected fellow eyes of patients with ONH showed mild features of underdevelopment. Visual acuity and presence of septo-optic dysplasia were associated with changes in GCL and IPL. Sensitivity and specificity for the detection of ONH based on disc and retinal optical coherence tomography (OCT) parameters were >80%. Conclusions Our study provides evidence of retinal changes in ONH. In addition to thinning of retina layers mainly involving the RNFL and GCL, signs reminiscent of foveal hypoplasia were observed in patients with ONH. Optic nerve and foveal parameters measured using OCT showed high sensitivity and specificity for detecting ONH, demonstrating their useful for clinical diagnosis. |
Avery Popien; Mallory Frayn; Kristin M. Ranson; Christopher R. Sears Eye gaze tracking reveals heightened attention to food in adults with binge eating when viewing images of real-world scenes Journal Article In: Appetite, vol. 91, pp. 233–240, 2015. @article{Popien2015, Individuals with eating disorders often exhibit food-related biases in attention tasks. To assess the engagement and maintenance of attention to food in adults with binge eating, in the present study, eye gaze tracking was used to compare fixations to food among non-clinical adults with versus without binge eating while they viewed images of real-world scenes. Fifty-seven participants' eye fixations were tracked and recorded throughout 8-second presentations of scenes containing high-calorie and/or low-caloriefood items in various settings (restaurants, social gatherings, etc.). Participants with binge eating fixated on both high-calorie and low-calorie food items significantly more than controls, and this was the case when the high- and low-calorie food items were presented in the same image and in different images. Participants with binge eating also fixated on food items significantly earlier in the presentations. A time course analysis that divided each 8-second presentation into 2-second intervals revealed that participants with binge eating attended to food items more than control participants throughout the 8-second presentation. These results have implications for theory regarding the initiation and maintenance of binge eating. |
Silvia Primativo; Lisa S. Arduino; Roberta Daini; Maria De Luca; Carlo Toneatto; Marialuisa Martelli Impaired oculo-motor behaviour affects both reading and scene perception in neglect patients Journal Article In: Neuropsychologia, vol. 70, pp. 90–106, 2015. @article{Primativo2015, Unilateral spatial neglect (USN) is a common neuropsychological disorder following a right-sided brain lesion. Although USN is mostly characterized by symptoms involving the left hemispace, other symptoms are not left lateralized. Recently, it was shown that patients with neglect dyslexia, a reading disturbance that affects about 40% of USN patients, manifest a non-lateralized impairment of eye movement behaviour in association with their reading deficit when they read aloud and perform non-verbal saccadic tasks (Primativo et al., 2013).In the present paper, we aimed to demonstrate that the eye movement impairment shown by some USN patients reflects a more general oculo-motor disorder that is not confined to orthographic material, the horizontal axis or constrained saccadic tasks. We conjectured that inaccurate oculo-motor behaviour in USN patients indicates the presence of a reading deficit. With this aim we evaluated 20 patients, i.e., 10 right-sided brain-damaged patients without neglect and 10 patients affected by USN. On the basis of the patients' eye movement patterns during a scene exploration task, we found that 4 out of the 10 USN patients presented an abnormal oculo-motor pattern. These same four patients (but not the others) also failed in performing 5 different saccadic tasks and produced neglect dyslexia reading errors in both single words and texts. First, we show that a large proportion of USN patients have inaccurate eye movement behaviour in non-reading tasks. Second, we demonstrate that this exploratory deficit is predictive of the reading impairment. Thus, we conclude that the eye movement deficit prevents reading and impairs the performance on many other perceptual tests, including scene exploration. The large percentage of patients with impaired eye-movement pattern suggests that particular attention should be paid to eye movement behaviour during the diagnostic phase in order to program the best rehabilitation strategy for each patient. |
Kate Rath-Wilson; Daniel Guitton Refuting the hypothesis that a unilateral human parietal lesion abolishes saccade corollary discharge Journal Article In: Brain, vol. 138, no. 12, pp. 3760–3775, 2015. @article{RathWilson2015, This paper questions the prominent role that the parietal lobe is thought to play in the processing of corollary discharges for saccadic eye movements. A corollary discharge copies the motor neurons' signal and sends it to brain areas involved in monitoring eye trajectories. The classic double-step saccade task has been used extensively to study these mechanisms: two targets (T1 and T2) are quickly (40-150 ms) flashed sequentially in the periphery. After the extinction of the fixation point, subjects are to make two saccades (S1 and S2), in the dark, to the remembered locations of the targets in the order they appeared. The success of S2 requires a corollary discharge encoding S1's vector. Patients with a parietal lobe lesion, particularly on the right, are impaired at generating an accurate S2 when S1 is directed contralesionally, but not ipsilesionally, thought due to an impaired contralesional corollary discharge. In contrast, we hypothesize that failure on the classic double-step task is due to visual processing and attentional deficits that commonly result from lesions of the parietal lobe and imperfect data analysis methods. Here, we studied parietal patients who fail in the classic double-step task when tested and data analysed according to previously published methods. We then tested our patients on two modified versions of the double-step task, designed to mitigate deficits other than corollary discharge that may have confounded previous investigations. In our 'exogenous' task, T2 was presented prior to T1 and for longer (T2: 800-1200 ms, T1: 350 ms) than in the classic task. S1 went to T1 and S2 to T2, all in the dark. All patients who completed sufficient trials had a corollary discharge for contralesional and ipsilesional S1s (5/5). In our 'endogenous' task, a single target was presented peripherally for 800-1200 ms. After extinction of target and fixation point, patients made first an 'endogenous' S1, of self-determined amplitude either to the left or right, before making S2 to the remembered location of the previously flashed target. To be successful, a corollary discharge of endogenous S1-generated in the dark-was required in the calculation of S2's motor vector. Every parietal patient showed evidence of using corollary discharges for endogenous S1s in the ipsilesional and contralesional directions (6/6). Our results support the hypothesis, based on our previous studies of corollary discharge mechanisms in hemidecorticate patients, and electrophysiological studies by others in monkey, that corollary discharges for left and right saccades are available to each cortical hemisphere. |
Kate Rath-Wilson; Daniel Guitton Oculomotor control after hemidecortication: A single hemisphere encodes corollary discharges for bilateral saccades Journal Article In: Cortex, vol. 63, pp. 232–249, 2015. @article{RathWilson2015a, Patients who have had a cerebral hemisphere surgically removed as adults can generate accurate leftward and rightward saccadic eye movements, a task classically thought to require two hemispheres each controlling contralateral saccades. Here, we asked whether one hemisphere can generate sequences of saccades, the success of which requires the use of corollary discharges. Using a double-step saccade paradigm, we tested two hemidecorticate subjects who, by definition, are contralesionally hemianopic. In experiment 1, two targets, T1 and T2, were flashed in their seeing hemifield and subjects had to look in the dark to T1, then T2. In experiment 2, only one target was flashed; before looking at it, the subject had first to saccade voluntarily elsewhere. Both subjects were able to complete the tasks, independent of first and second saccade direction and whether the saccades were voluntarily or visually triggered. Both subjects displayed a strategy, typical in hemianopia, of making multiple-step saccades and placing, at overall movement-end, the recalled locations of T1 and T2 on off-foveal locations in their seeing hemifield, in a retinal area typically spanning a 5-15° window, depending on the subject, trial type and target eccentricity. In summary, a single hemisphere monitored the amplitude and direction of the first multiple-step saccade sequence bilaterally, and combined this information with the recalled initial retinotopic location of T2 (no longer visible) to generate a correct target-directed second saccade sequence in the dark. Unexpectedly, our hemidecorticate subjects performed better on the double-step task than subjects with isolated unilateral parietal lesions, reported in the literature to have marked deficiencies in monitoring contralesional saccadic eye movements. Thus, plasticity-dependent mechanisms that lead to recovery of function after hemidecortication are different than those deployed after smaller lesions. This implies a reconsideration of the classical links between behavioural deficits and discrete cortical lesions. |
Aditi Subramaniam; Sri Mahavir Agarwal; Sunil Kalmady; Venkataram Shivakumar; Harleen Chhabra; Anushree Bose; Dinakaran Damodharan; Janardhanan C. Narayanaswamy; Samuel B. Hutton; Ganesan Venkatasubramanian In: Indian Journal of Psychological Medicine, vol. 37, no. 4, pp. 419–422, 2015. @article{Subramaniam2015, Background: Deficient prefrontal cortex inhibitory control is of particular interest with regard to the pathogenesis of auditory hallucinations (AHs) in schizophrenia. Antisaccade task performance is a sensitive index of prefrontal inhibitory function and has been consistently found to be abnormal in schizophrenia. Methods: This study investigated the effect of transcranial direct current stimulation (tDCS) on antisaccade performance in 13 schizophrenia patients. Results: The tDCS resulted in significant reduction in antisaccade error percentage (t = 3.4; P = 0.005), final eye position gain (t = 2.3; P = 0.042), and AHs severity (t = 4.1; P = 0.003). Conclusion: Our results raise the possibility that improvement in antisaccade performance and severity of AH may be mechanistically related. |
Katharine N. Thakkar; Jeffrey D. Schall; Stephan Heckers; Sohee Park Disrupted saccadic corollary discharge in schizophrenia Journal Article In: Journal of Neuroscience, vol. 35, no. 27, pp. 9935–9945, 2015. @article{Thakkar2015, Disruptions in corollary discharge (CD), motor signals that send information to sensory areas and allow for prediction of sensory states, are argued to underlie the perceived loss of agency in schizophrenia. Behavioral and neurophysiological evidence for CD in primates comes largely from the saccadic double-step task, which requires participants to make two visually triggered saccadic eye movements in brief succession. Healthy individuals use CD to anticipate the change in eye position resulting from the first saccade when preparing the second saccade. In the current study with human participants, schizophrenia patients and healthy controls of both sexes performed a modified double-step task. Most trials required a saccade to a single visual target (T1). On a subset of trials, a second target (T2) was flashed shortly following T1. Subjects were instructed to look directly at T2. Healthy individuals also use CD to make rapid, corrective responses following erroneous saccades to T1. To assess CD in schizophrenia, we examined the following on error trials: (1) frequency and latency of corrective saccades, and (2) mislocalization of the corrective (second) saccade in the direction predicted by a failure to use CD to account for the first eye movement. Consistent with disrupted CD, patients made fewer and slower error corrections. Importantly, the corrective saccade vector angle was biased in a manner consistent with disrupted CD. These results provide novel and clear evidence for dysfunctional CD in the oculomotor system in patients with schizophrenia. Based on neurophysiology work, these disturbances might have their basis in medial thalamus dysfunction. |
Katharine N. Thakkar; Jeffrey D. Schall; Gordon D. Logan; Sohee Park Cognitive control of gaze in bipolar disorder and schizophrenia Journal Article In: Psychiatry Research, vol. 225, no. 3, pp. 254–262, 2015. @article{Thakkar2015a, The objective of the present study was to compare two components of executive functioning, response monitoring and inhibition, in bipolar disorder (BP) and schizophrenia (SZ). The saccadic countermanding task is a translational paradigm optimized for detecting subtle abnormalities in response monitoring and response inhibition. We have previously reported countermanding performance abnormalities in SZ, but the degree to which these impairments are shared by other psychotic disorders is unknown. 18 BP, 17 SZ, and 16 demographically matched healthy controls (HC) participated in a saccadic countermanding task. Performance on the countermanding task is approximated as a race between movement generation and inhibition processes; this model provides an estimate of the time needed to cancel a planned movement. Response monitoring was assessed by the reaction time (RT) adjustments based on trial history. Like SZ patients, BP patients needed more time to cancel a planned movement. The two patient groups had equivalent inhibition efficiency. On trial history-based RT adjustments, however, we found a trend towards exaggerated trial history-based slowing in SZ compared to BP. Findings have implications for understanding the neurobiology of cognitive control, for defining the etiological overlap between schizophrenia and bipolar disorder, and for developing pharmacological treatments of cognitive impairments. |
Katharine N. Thakkar; Jeffrey D. Schall; Gordon D. Logan; Sohee Park Response inhibition and response monitoring in a saccadic double-step task in schizophrenia Journal Article In: Brain and Cognition, vol. 95, pp. 90–98, 2015. @article{Thakkar2015b, Background: Cognitive control impairments are linked to functional outcome in schizophrenia. The goal of the current study was to investigate precise abnormalities in two aspects of cognitive control: reactively changing a prepared response, and monitoring performance and adjusting behavior accordingly. We adapted an oculomotor task from neurophysiological studies of the cellular basis of cognitive control in nonhuman primates. Methods: 16 medicated outpatients with schizophrenia (SZ) and 18 demographically-matched healthy controls performed the modified double-step task. In this task, participants were required to make a saccade to a visual target. Infrequently, the target jumped to a new location and participants were instructed to rapidly inhibit and change their response. A race model provided an estimate of the time needed to cancel a planned movement. Response monitoring was assessed by measuring reaction time (RT) adjustments based on trial history. Results: SZ patients had normal visually-guided saccadic RTs but required more time to switch the response to the new target location. Additionally, the estimated latency of inhibition was longer in patients and related to employment. Finally, although both groups slowed down on trials that required inhibiting and changing a response, patients showed exaggerated performance-based adjustments in RTs, which was correlated with positive symptom severity. Conclusions: SZ patients have impairments in rapidly inhibiting eye movements and show idiosyncratic response monitoring. These results are consistent with functional abnormalities in a network involving cortical oculomotor regions, the superior colliculus, and basal ganglia, as described in neurophysiological studies of non-human primates using an identical paradigm, and provide a translational bridge for understanding cognitive symptoms of SZ. |
Kate M. Thompson; Tracy L. Taylor Memory instruction interacts with both visual and motoric inhibition of return Journal Article In: Attention, Perception, and Psychophysics, vol. 77, no. 3, pp. 804–818, 2015. @article{Thompson2015, In the item-method directed forgetting paradigm, the magnitude of inhibition of return (IOR) is larger after an instruction to forget (F) than after an instruction to remember (R). In the present experiments, we further investigated this increased magnitude of IOR after F than after R memory instructions, to determine whether this F > R IOR pattern occurs only for the motoric form of IOR, as predicted, or also for the visual form. In three experiments, words were presented in one of two peripheral locations, followed by either an F or an R memory instruction. Then, a target appeared either at the same location as the previous word or at the other location. In Experiment 1, participants maintained fixation throughout the trial until the target appeared, at which point they made a saccade to the target. In Experiment 2, they maintained fixation throughout the entire trial and made a manual localization response to the target. The F > R IOR difference in reaction times occurred for both the saccadic and manual responses, suggesting that memory instructions modify both motoric and visual forms of IOR. In Experiment 3, participants made a perceptual discrimination response to report the identity of a target while the eyes remained fixed. The F > R IOR difference also occurred for these manual discrimination responses, increasing our confidence that memory instructions modify the visual form of IOR. We relate our findings to postulated differences in attentional withdrawal following F and R instructions and consider the implications of the findings for successful forgetting. |
Wei Lin Toh; David J. Castle; Susan Lee Rossell Facial affect recognition in body dysmorphic disorder versus obsessive-compulsive disorder: An eye-tracking study Journal Article In: Journal of Anxiety Disorders, vol. 35, pp. 49–59, 2015. @article{Toh2015, Background: Body dysmorphic disorder (BDD) is characterised by repetitive behaviours and/or mental acts occurring in response to preoccupations with perceived defects or flaws in physical appearance (American Psychiatric Association, 2013). This study aimed to investigate facial affect recognition in BDD using an integrated eye-tracking paradigm. Method: Participants were 21 BDD patients, 19 obsessive-compulsive disorder (OCD) patients and 21 healthy controls (HC), who were age-, sex-, and IQ-matched. Stimuli were from the Pictures of Facial Affect (Ekman & Friesen, 1975), and outcome measures were affect recognition accuracy as well as spatial and temporal scanpath parameters. Results: Relative to OCD and HC groups, BDD patients demonstrated significantly poorer facial affect perception and an angry recognition bias. An atypical scanning strategy encompassing significantly more blinks, fewer fixations of extended mean durations, higher mean saccade amplitudes, and less visual attention devoted to salient facial features was found. Conclusions: Patients with BDD were substantially impaired in the scanning of faces, and unable to extract affect-related information, likely indicating deficits in basic perceptual operations. |
Avinash R. Vaidya; Lesley K. Fellows Testing necessary regional frontal contributions to value assessment and fixation-based updating Journal Article In: Nature Communications, vol. 6, pp. 10120, 2015. @article{Vaidya2015, Value-based decisions are biased by the time people spend viewing each option: Options fixated longer are chosen more often, even when previously rated as less appealing. This bias is thought to reflect /`value updating/' as new evidence is accumulated. Prior work has shown that ventromedial prefrontal cortex (PFC) carries a fixation-dependent value comparison signal, while other studies implicate dorsomedial PFC in representing the value of alternative options. Here, we test whether these regions are necessary for fixation-related value updating in 33 people with frontal lobe damage and 27 healthy controls performing a simple choice task. We show that damage to dorsomedial PFC leads to an exaggerated influence of fixations on choice, while damage to ventromedial or lateral PFC has no effect on this bias. These findings suggest a critical role for dorsomedial, and not ventromedial PFC, in mediating the relative influence of current fixations and a priori value on choice. |
Goedele Van Belle; Philippe Lefèvre; Bruno Rossion Face inversion and acquired prosopagnosia reduce the size of the perceptual field of view Journal Article In: Cognition, vol. 136, no. 1, pp. 403–408, 2015. @article{VanBelle2015, Using a gaze-contingent morphing approach, we asked human observers to choose one of two faces that best matched the identity of a target face: one face corresponded to the reference face's fixated part only (e.g., one eye), the other corresponded to the unfixated area of the reference face. The face corresponding to the fixated part was selected significantly more frequently in the inverted than in the upright orientation. This observation provides evidence that face inversion reduces an observer's perceptual field of view, even when both upright and inverted faces are displayed at full view and there is no performance difference between these conditions. It rules out an account of the drop of performance for inverted faces - one of the most robust effects in experimental psychology - in terms of a mere difference in local processing efficiency. A brain-damaged patient with pure prosopagnosia, viewing only upright faces, systematically selected the face corresponding to the fixated part, as if her perceptual field was reduced relative to normal observers. Altogether, these observations indicate that the absence of visual knowledge reduces the perceptual field of view, supporting an indirect view of visual perception. |
Lara Rösler; Martin Rolfs; Stefan Stigchel; Sebastiaan F. W. Neggers; Wiepke Cahn; René S. Kahn; Katharine N. Thakkar Failure to use corollary discharge to remap visual target locations is associated with psychotic symptom severity in schizophrenia Journal Article In: Journal of Neurophysiology, vol. 114, no. 2, pp. 1129–1136, 2015. @article{Roesler2015, Corollary discharge (CD) refers to "copies" of motor signals sent to sensory areas, allowing prediction of future sensory states. They enable the putative mechanisms supporting the distinction between self-generated and externally generated sensations. Accordingly, many authors have suggested that disturbed CD engenders psychotic symptoms of schizophrenia, which are characterized by agency distortions. CD also supports perceived visual stability across saccadic eye movements and is used to predict the postsaccadic retinal coordinates of visual stimuli, a process called remapping. We tested whether schizophrenia patients (SZP) show remapping disturbances as evidenced by systematic transsaccadic mislocalizations of visual targets. SZP and healthy controls (HC) performed a task in which a saccadic target disappeared upon saccade initiation and, after a brief delay, reappeared at a horizontally displaced position. HC judged the direction of this displacement accurately, despite spatial errors in saccade landing site, indicating that their comparison of the actual to predicted postsaccadic target location relied on accurate CD. SZP performed worse and relied more on saccade landing site as a proxy for the presaccadic target, consistent with disturbed CD. This remapping failure was strongest in patients with more severe psychotic symptoms, consistent with the theoretical link between disturbed CD and phenomenological experiences in schizophrenia. |
Lars A. Ross; Victor A. Del Bene; Sophie Molholm; Hans Peter Frey; John J. Foxe Sex differences in multisensory speech processing in both typically developing children and those on the autism spectrum Journal Article In: Frontiers in Neuroscience, vol. 9, pp. 185, 2015. @article{Ross2015, Background: Previous work has revealed sizeable deficits in the abilities of children with an autism spectrum disorder (ASD) to integrate auditory and visual speech signals, with clear implications for social communication in this population. There is a strong male preponderance in ASD, with approximately four affected males for every female. The presence of sex differences in ASD symptoms suggests a sexual dimorphism in the ASD phenotype, and raises the question of whether this dimorphism extends to ASD traits in the neurotypical population. Here, we investigated possible sexual dimorphism in multisensory speech integration in both ASD and neurotypical individuals. Methods: We assessed whether males and females differed in their ability to benefit from visual speech when target words were presented under varying levels of signal-to-noise, in samples of neurotypical children and adults, and in children diagnosed with an ASD. Results: In typically developing (TD) children and children with ASD, females (n= 47 and n=15 respectively) were significantly superior in their ability to recognize words under audiovisual listening conditions compared to males (n= 55 and n=58 respectively). This sex difference was absent in our sample of neurotypical adults (n= 28 females; n= 28 males). Conclusions: We propose that the development of audiovisual integration is delayed in male relative to female children, a delay that is also observed in ASD. In neurotypicals, these sex differences disappear in early adulthood when females approach their performance maximum and males “catch up”. Our findings underline the importance of considering sex differences in the search for autism endophenotypes and strongly encourage increased efforts to study the underrepresented population of females within ASD. |
Paul Roux; Christine Passerieux; Franck Ramus An eye-tracking investigation of intentional motion perception in patients with schizophrenia Journal Article In: Journal of Psychiatry and Neuroscience, vol. 40, no. 2, pp. 118–125, 2015. @article{Roux2015, BACKGROUND: Schizophrenia has been characterized by an impaired attribution of intentions in social interactions. However, it remains unclear to what extent poor performance may be due to low-level processes or to later, higher-level stages or to what extent the deficit reflects an over- (hypermentalization) or underattribution of intentions (hypomentalization). METHODS: We evaluated intentional motion perception using a chasing detection paradigm in individuals with schizophrenia or schizoaffective disorder and in healthy controls while eye movements were recorded. Smooth pursuit was measured as a control task. Eye-tracking was used to dissociate ocular from cognitive stages of processing. RESULTS: We included 27 patients with schizophrenia, 2 with schizoaffective disorder and 29 controls in our analysis. As a group, patients had lower sensitivity to the detection of chasing than controls, but showed no bias toward the chasing present response. Patients showed a slightly different visual exploration strategy, which affected their ocular sensitivity to chasing. They also showed a decreased cognitive sensitivity to chasing that was not explained by differences in smooth pursuit ability, in visual exploration strategy or in general cognitive abilities. LIMITATIONS: It is not clear whether the deficit in intentional motion detection demonstrated in this study might be explained by a general deficit in motion perception in individuals with schizophrenia or whether it is specific to the social domain. CONCLUSION: Participants with schizophrenia showed a hypomentalization deficit: they adopted suboptimal visual exploration strategies and had difficulties deciding whether a chase was present or not, even when their eye movement revealed that chasing information had been seen correctly. |
Uzma Samadani; Sameer Farooq; Robert Ritlop; Floyd Warren; Marleen Reyes; Elizabeth Lamm; Anastasia Alex; Elena Nehrbass; Radek Kolecki; Michael Jureller; Julia Schneider; Agnes Chen; Chen Shi; Neil Mendhiratta; Jason H. Huang; Meng Qian; Roy Kwak; Artem Mikheev; Henry Rusinek; Ajax George; Robert Fergus; Douglas Kondziolka; Paul P. Huang; R. Theodore Smith Detection of third and sixth cranial nerve palsies with a novel method for eye tracking while watching a short film clip Journal Article In: Journal of Neurosurgery, vol. 122, pp. 707–720, 2015. @article{Samadani2015, OBJECT: Automated eye movement tracking may provide clues to nervous system function at many levels. Spatial calibration of the eye tracking device requires the subject to have relatively intact ocular motility that implies function of cranial nerves (CNs) III (oculomotor), IV (trochlear), and VI (abducent) and their associated nuclei, along with the multiple regions of the brain imparting cognition and volition. The authors have developed a technique for eye tracking that uses temporal rather than spatial calibration, enabling detection of impaired ability to move the pupil relative to normal (neurologically healthy) control volunteers. This work was performed to demonstrate that this technique may detect CN palsies related to brain compression and to provide insight into how the technique may be of value for evaluating neuropathological conditions associated with CN palsy, such as hydrocephalus or acute mass effect. METHODS: The authors recorded subjects' eye movements by using an Eyelink 1000 eye tracker sampling at 500 Hz over 200 seconds while the subject viewed a music video playing inside an aperture on a computer monitor. The aperture moved in a rectangular pattern over a fixed time period. This technique was used to assess ocular motility in 157 neurologically healthy control subjects and 12 patients with either clinical CN III or VI palsy confirmed by neuro-ophthalmological examination, or surgically treatable pathological conditions potentially impacting these nerves. The authors compared the ratio of vertical to horizontal eye movement (height/width defined as aspect ratio) in normal and test subjects. RESULTS: In 157 normal controls, the aspect ratio (height/width) for the left eye had a mean value ± SD of 1.0117 ± 0.0706. For the right eye, the aspect ratio had a mean of 1.0077 ± 0.0679 in these 157 subjects. There was no difference between sexes or ages. A patient with known CN VI palsy had a significantly increased aspect ratio (1.39), whereas 2 patients with known CN III palsy had significantly decreased ratios of 0.19 and 0.06, respectively. Three patients with surgically treatable pathological conditions impacting CN VI, such as infratentorial mass effect or hydrocephalus, had significantly increased ratios (1.84, 1.44, and 1.34, respectively) relative to normal controls, and 6 patients with supratentorial mass effect had significantly decreased ratios (0.27, 0.53, 0.62, 0.45, 0.49, and 0.41, respectively). These alterations in eye tracking all reverted to normal ranges after surgical treatment of underlying pathological conditions in these 9 neurosurgical cases. CONCLUSIONS: This proof of concept series of cases suggests that the use of eye tracking to detect CN palsy while the patient watches television or its equivalent represents a new capacity for this technology. It may provide a new tool for the assessment of multiple CNS functions that can potentially be useful in the assessment of awake patients with elevated intracranial pressure from hydrocephalus or trauma. |
Uzma Samadani; Meng Qian Li; Eugene Laska; Robert Ritlop; Robert Kolecki; Marleen Reyes; Lindsey Altomare; Je Yeong Sone; Aylin Adem; Paul P. Huang; Douglas Kondziolka; Stephen Wall; Spiros Frangos; Charles Marmar Sensitivity and specificity of an eye movement tracking-based biomarker for concussion Journal Article In: Concussion, vol. 1, no. 1, pp. 1–14, 2015. @article{Samadani2015a, Object: The purpose of the current study is to determine the sensitivity and specificity of an eye tracking method as a classifier for identifying concussion. Methods: Brain injured and control subjects prospectively underwent both eye tracking and Sport Concussion Assessment Tool 3. The results of eye tracking biomarker based classifier models were then validated against a dataset of individuals not used in building a model. The area under the curve (AUC) of receiver operating characteristics was examined. Results: An optimal classifier based on best subset had an AUC of 0.878, and a cross-validated AUC of 0.852 in CT- subjects and an AUC of 0.831 in a validation dataset. The optimal misclassification rate in an external dataset (n = 254) was 13%. Conclusion: If one defines concussion based on history, examination, radiographic and Sport Concussion Assessment Tool 3 criteria, it is possible to generate an eye tracking based biomarker that enables detection of concussion with reasonably high sensitivity and specificity. |
Uzma Samadani; Robert Ritlop; Marleen Reyes; Elena Nehrbass; Meng Li; Elizabeth Lamm; Julia Schneider; David Shimunov; Maria Sava; Radek Kolecki; Paige Burris; Lindsey Altomare; Talha Mehmood; Theodore Smith; Jason H. Huang; Christopher McStay; S. Rob Todd; Meng Qian; Douglas Kondziolka; Stephen Wall; Paul P. Huang Eye tracking detects disconjugate eye movements associated with structural traumatic brain injury and concussion Journal Article In: Journal of Neurotrauma, vol. 32, no. 8, pp. 548–556, 2015. @article{Samadani2015b, Disconjugate eye movements have been associated with traumatic brain injury since ancient times. Ocular motility dysfunction may be present in up to 90% of patients with concussion or blast injury. We developed an algorithm for eye tracking in which the Cartesian coordinates of the right and left pupils are tracked over 200 sec and compared to each other as a subject watches a short film clip moving inside an aperture on a computer screen. We prospectively eye tracked 64 normal healthy noninjured control subjects and compared findings to 75 trauma subjects with either a positive head computed tomography (CT) scan (n=13), negative head CT (n=39), or nonhead injury (n=23) to determine whether eye tracking would reveal the disconjugate gaze associated with both structural brain injury and concussion. Tracking metrics were then correlated to the clinical concussion measure Sport Concussion Assessment Tool 3 (SCAT3) in trauma patients. Five out of five measures of horizontal disconjugacy were increased in positive and negative head CT patients relative to noninjured control subjects. Only one of five vertical disconjugacy measures was significantly increased in brain-injured patients relative to controls. Linear regression analysis of all 75 trauma patients demonstrated that three metrics for horizontal disconjugacy negatively correlated with SCAT3 symptom severity score and positively correlated with total Standardized Assessment of Concussion score. Abnormal eye-tracking metrics improved over time toward baseline in brain-injured subjects observed in follow-up. Eye tracking may help quantify the severity of ocular motility disruption associated with concussion and structural brain injury. |
Timothy J. Shakespeare; Yoni Pertzov; Keir X. X. Yong; Jennifer M. Nicholas; Sebastian J. Crutch Reduced modulation of scanpaths in response to task demands in posterior cortical atrophy Journal Article In: Neuropsychologia, vol. 68, pp. 190–200, 2015. @article{Shakespeare2015a, A difficulty in perceiving visual scenes is one of the most striking impairments experienced by patients with the clinico-radiological syndrome posterior cortical atrophy (PCA). However whilst a number of studies have investigated perception of relatively simple experimental stimuli in these individuals, little is known about multiple object and complex scene perception and the role of eye movements in posterior cortical atrophy. We embrace the distinction between high-level (top-down) and low-level (bottom-up) influences upon scanning eye movements when looking at scenes. This distinction was inspired by Yarbus (1967), who demonstrated how the location of our fixations is affected by task instructions and not only the stimulus' low level properties. We therefore examined how scanning patterns are influenced by task instructions and low-level visual properties in 7 patients with posterior cortical atrophy, 8 patients with typical Alzheimer's disease, and 19 healthy age-matched controls.Each participant viewed 10 scenes under four task conditions (encoding, recognition, search and description) whilst eye movements were recorded. The results reveal significant differences between groups in the impact of test instructions upon scanpaths. Across tasks without a search component, posterior cortical atrophy patients were significantly less consistent than typical Alzheimer's disease patients and controls in where they were looking. By contrast, when comparing search and non-search tasks, it was controls who exhibited lowest between-task similarity ratings, suggesting they were better able than posterior cortical atrophy or typical Alzheimer's disease patients to respond appropriately to high-level needs by looking at task-relevant regions of a scene. Posterior cortical atrophy patients had a significant tendency to fixate upon more low-level salient parts of the scenes than controls irrespective of the viewing task. The study provides a detailed characterisation of scene perception abilities in posterior cortical atrophy and offers insights into the mechanisms by which high-level cognitive schemes interact with low-level perception. |
Annie L. Shelton; Kim M. Cornish; David E. Godler; Meaghan Clough; Claudine Kraan; Minh Bui; Joanne Fielding Delineation of the working memory profile in female FMR1 premutation carriers: The effect of cognitive load on ocular motor responses Journal Article In: Behavioural Brain Research, vol. 282, pp. 194–200, 2015. @article{Shelton2015, Fragile X mental retardation 1 (FMR1) premutation carriers (PM-carriers) are characterised as having mid-sized expansions of between 55 and 200 CGG repeats in the 5' untranslated region of the FMR1 gene. While there is evidence of executive dysfunction in PM-carriers, few studies have explicitly explored working memory capabilities in female PM-carriers. 14 female PM-carriers and 13 age- and IQ-matched healthy controls completed an ocular motor n-back working memory paradigm. This task examined working memory ability and the effect of measured increases in cognitive load. Female PM-carriers were found to have attenuated working memory capabilities. Increasing the cognitive load did not elicit the expected reciprocal increase in the task errors for female PM-carriers, as it did in controls. However female PM-carriers took longer to respond than controls, regardless of the cognitive load. Further, FMR1 mRNA levels were found to significantly predict PM-carrier response time. Although preliminary, these findings provide further evidence of executive dysfunction, specifically disruption to working memory processes, which were found to be associated with increases in FMR1 mRNA expression in female PM-carriers. With future validation, ocular motor paradigms such as the n-back paradigm will be critical to the development of behavioural biomarkers for identification of PM-carrier cognitive-affective phenotypes. |
Lijuan Shi; Yuanyue Zhou; Jianjun Ou; Jingbo Gong; Suhong Wang; Xilong Cui; Hailong Lyu; Jingping Zhao; Xuerong Luo In: PLoS ONE, vol. 10, no. 3, pp. e0122280, 2015. @article{Shi2015, Eye-tracking studies in young children with autism spectrum disorder (ASD) have shown a visual attention preference for geometric patterns when viewing paired dynamic social images (DSIs) and dynamic geometric images (DGIs). In the present study, eye-tracking of two different paired presentations of DSIs and DGIs was monitored in a group of 13 children aged 4 to 6 years with ASD and 20 chronologically age-matched typically developing children (TDC). The results indicated that compared with the control group, children with ASD attended significantly less to DSIs showing two or more children playing than to similar DSIs showing a single child. Visual attention preference in 4- to 6-year-old children with ASDs, therefore, appears to be modulated by the type of visual stimuli. |
Martha M. Shiell; François Champoux; Robert J. Zatorre Reorganization of auditory cortex in early-deaf people: Functional connectivity and relationship to hearing aid use Journal Article In: Journal of Cognitive Neuroscience, vol. 27, no. 1, pp. 150–163, 2015. @article{Shiell2015, Cross-modal reorganization after sensory deprivation is a model for understanding brain plasticity. Although it is a well- documented phenomenon, we still know little of the mecha- nisms underlying it or the factors that constrain and promote it. Using fMRI, we identified visual motion-related activity in 17 early-deaf and 17 hearing adults. We found that, in the deaf, the posterior superior temporal gyrus (STG) was responsive to visual motion. We compared functional connectivity of this re- organized cortex between groups to identify differences in func- tional networks associated with reorganization. In the deaf more than the hearing, the STG displayed increased functional connec- tivity with a region in the calcarine fissure. We also explored the role ofhearing aid use, a factor that may contribute to variability in cross-modal reorganization. We found that both the cross-modal activity in STG and the functional connectivity between STG and calcarine cortex correlated with duration of hearing aid use, sup- porting the hypothesis that residual hearing affects cross-modal reorganization. We conclude that early auditory deprivation alters not only the organization of auditory regions but also the inter- actions between auditory and primary visual cortex and that audi- tory input, as indexed by hearing aid use, may inhibit cross-modal reorganization in early-deaf people. |
Sabine Soltani; Kristin R. Newman; Leanne Quigley; Amanda Fernandez; Keith S. Dobson; Christopher Sears Temporal changes in attention to sad and happy faces distinguish currently and remitted depressed individuals from never depressed individuals Journal Article In: Psychiatry Research, vol. 230, no. 2, pp. 454–463, 2015. @article{Soltani2015, Depression is associated with attentional biases for emotional information that are proposed to reflect stable vulnerability factors for the development and recurrence of depression. A key question for researchers is whether those who have recovered from depression also exhibit attentional biases, and if so, how similar these biases are to those who are currently depressed. To address this question, the present study examined attention to emotional faces in remitted depressed (N=26), currently depressed (N=16), and never depressed (N=33) individuals. Participants viewed sets of four face images (happy, sad, threatening, and neutral) while their eye movements were tracked throughout an 8-s presentation. Like currently depressed participants, remitted depressed participants attended to sad faces significantly more than never depressed participants and attended to happy faces significantly less. Analyzing temporal changes in attention revealed that currently and remitted depressed participants did not reduce their attention to sad faces over the 8-s presentation, unlike never depressed participants. In contrast, remitted depressed participants attended to happy faces similarly to never depressed participants, increasing their attention to happy faces over the 8-s presentation. The implications for cognitive theories of depression and depression vulnerability are discussed. |
Gregory P. Strauss; Emily S. Kappenman; Adam J. Culbreth; Lauren T. Catalano; Kathryn L. Ossenfort; Bern G. Lee; James M. Gold In: Journal of Abnormal Psychology, vol. 124, no. 2, pp. 288–301, 2015. @article{Strauss2015, Previous research provides evidence that individuals with schizophrenia (SZ) have emotion regulation abnormalities, particularly when attempting to use reappraisal to decrease negative emotion. The current study extended this literature by examining the effectiveness of a different form of emotion regulation, directed attention, which has been shown to be effective at reducing negative emotion in healthy individuals. Participants included outpatients with SZ (n = 28) and healthy controls (CN: n = 25), who viewed unpleasant and neutral images during separate event-related potential and eye-movement tasks. Trials included both passive viewing and directed attention segments. During directed attention, gaze was directed toward highly arousing aspects of an unpleasant image, less arousing aspects of an unpleasant image, or a nonarousing aspect of a neutral image. The late positive potential (LPP) event-related potential component indexed emotion regulation success. Directing attention to nonarousing aspects of unpleasant images decreased the LPP in CN; however, SZ showed similar LPP amplitude when attention was directed toward more or less arousing aspects of unpleasant scenes. Eye tracking indicated that SZ were more likely than CN to attend to arousing portions of unpleasant scenes when attention was directed toward less arousing scene regions. Furthermore, pupilary data suggested that SZ patients failed to engage effortful cognitive processes needed to inhibit the prepotent response of attending to arousing aspects of unpleasant scenes when attention was directed toward nonarousing scene regions. Findings add to the growing literature indicating that individuals with SZ display emotion regulation abnormalities and provide novel evidence that dysfunctional emotion-attention interactions and generalized cognitive control deficits are associated with ineffective use of directed attention strategies to regulate negative emotion. |
Falk Huettig; Susanne Brouwer Delayed anticipatory spoken language processing in adults with dyslexia - Evidence from eye-tracking Journal Article In: Dyslexia, vol. 21, no. 2, pp. 97–122, 2015. @article{Huettig2015, It is now well established that anticipation of upcoming input is a key characteristic of spoken language comprehension. It has also frequently been observed that literacy influences spoken language processing. Here, we investigated whether anticipatory spoken language processing is related to individuals' word reading abilities. Dutch adults with dyslexia and a control group participated in two eye-tracking experiments. Experiment 1 was conducted to assess whether adults with dyslexia show the typical language-mediated eye gaze patterns. Eye movements of both adults with and without dyslexia closely replicated earlier research: spoken language is used to direct attention to relevant objects in the environment in a closely time-locked manner. In Experiment 2, participants received instructions (e.g., 'Kijk naar deCOM afgebeelde pianoCOM ', look at the displayed piano) while viewing four objects. Articles (Dutch 'het' or 'de') were gender marked such that the article agreed in gender only with the target, and thus, participants could use gender information from the article to predict the target object. The adults with dyslexia anticipated the target objects but much later than the controls. Moreover, participants' word reading scores correlated positively with their anticipatory eye movements. We conclude by discussing the mechanisms by which reading abilities may influence predictive language processing. |
Rebecca L. Johnson; Ann Marie Raphail Untangling letter confusability and word length effects in pure alexia Journal Article In: Cognitive Neuropsychology, vol. 32, no. 7-8, pp. 442–456, 2015. @article{Johnson2015, Pure alexia is an acquired neuropsychological disorder that follows damage to the occipito-temporal lobe. This brain damage results in a severe reading impairment in which previously literate individuals are no longer able to efficiently read words, but are still able to perform other language tasks. The present study sought to identify factors of words that make it more difficult for pure alexic individuals to read, such as letter confusability and word length. Eye-tracking methodology was paired with a naming task to examine whether word length or letter confusability is a better predictor of processing difficulty. It was found that word length was a significant predictor of reading time, while summed letter confusability was not significant. This study contradicts some previous research and shows that when an orthogonal set of stimuli is used, letter confusability is not a significant factor driving this reading impairment in all individuals with pure alexia. |
Jessica Knilans; Gayle DeDe Online sentence reading in people with aphasia: Evidence from eye tracking Journal Article In: American Journal of Speech-Language Pathology, vol. 24, no. 4, pp. S961–S973, 2015. @article{Knilans2015, PURPOSE: There is a lot of evidence that people with aphasia have more difficulty understanding structurally complex sentences (e.g., object clefts) than simpler sentences (subject clefts). However, subject clefts also occur more frequently in English than object clefts. Thus, it is possible that both structural complexity and frequency affect how people with aphasia understand these structures. METHOD: Nine people with aphasia and 8 age-matched controls participated in the study. The stimuli consisted of 24 object cleft and 24 subject cleft sentences. The task was eye tracking during reading, which permits a more fine-grained analysis of reading performance than measures such as self-paced reading. RESULTS: As expected, controls had longer reading times for critical regions in object cleft sentences compared with subject cleft sentences. People with aphasia showed the predicted effects of structural frequency. Effects of structural complexity in people with aphasia did not emerge on their first pass through the sentence but were observed when they were rereading critical regions of complex sentences. CONCLUSIONS: People with aphasia are sensitive to both structural complexity and structural frequency when reading. However, people with aphasia may use different reading strategies than controls when confronted with relatively infrequent and complex sentence structures. |
Makoto Kobayashi Unidirectional ocular flutter: Report of a case with abnormal saccadic characteristics Journal Article In: Neurological Sciences, vol. 36, no. 7, pp. 1273–1276, 2015. @article{Kobayashi2015, Presents a case report of a unique case of unidirectional ocular flutter (OF) with event frequency much lower than in the previous unidirectional OF case, displacement magnitudes larger than observed in double saccadic pulses (another involuntary saccade syndrome), and saccadic peak velocities substantially slower than visually guided saccades (VGSs). The 38 year old male was referred to our department because of a 2-month history of involuntary eye movements. His medical history included depression, for which he was prescribed duloxetine hydrochloride, bromazepam, olanzapine, and zolpidem tartrate. The termed saccadic intrusions, usually occur horizontally with directional predominance in each normal individual. Perhaps, saccadic intrusions observed in normal subjects and unidirectional OF may share a common directional predominance mechanism. |
Joanna R. Wares; David X. Cifu; Kathy W. Hoke; Paul A. Wetzel; George T. Gitchel; William Carne Differential eye movements in mild traumatic brain injury versus normal controls Journal Article In: Journal of Head Trauma Rehabilitation, vol. 30, no. 1, pp. 21–28, 2015. @article{Wares2015, Objectives: Objective measures to diagnose and to monitor improvement of symptoms following mild traumatic brain injury (mTBI) are lacking. Computerized eye tracking has been advocated as a rapid, user friendly, and field-ready technique to meet this need. Design: Eye-tracking data collected via a head-mounted, video-based binocular eye tracker was used to examine saccades, fixations, and smooth pursuit movement in military Service Members with postconcussive syndrome (PCS) and asymptomatic control subjects in an effort to determine if eye movement differences could be found and quantified. Participants: Sixty Military Service Members with PCS and 26 asymptomatic controls. Outcome measures: The diagnosis of mTBI was confirmed by the study physiatrist's history, physical examination, and a review of any medical records. Various features of saccades, fixation and smooth pursuit eye movements were analyzed. Results: Subjects with symptomatic mTBI had statistically larger position errors, smaller saccadic amplitudes, smaller predicted peak velocities, smaller peak accelerations, and longer durations. Subjects with symptomatic mTBI were also less likely to follow a target movement (less primary saccades). In general, symptomatic mTBI tracked the stepwise moving targets less accurately, revealing possible brain dysfunction. Conclusions: A reliable, standardized protocol that appears to differentiate mTBI from normals was developed for use in future research. This investigation represents a step toward objective identification of those with PCS. Future studies focused on increasing the specificity of eye movement differences in those with PCS are needed. |
Ming Yan; Jinger Pan; Nathalie N. Bélanger; Hua Shu Chinese deaf readers have early access to parafoveal semantics Journal Article In: Journal of Experimental Psychology: Learning, Memory, and Cognition, vol. 41, no. 1, pp. 254–261, 2015. @article{Yan2015c, In the present study, we manipulated different types of information available in the parafovea during the reading of Chinese sentences and examined how deaf readers make use of the parafoveal information. Results clearly indicate that although the reading-level matched hearing readers make greater use of orthographic information in the parafovea, parafoveal semantic information is obtained earlier among the deaf readers. In addition, a phonological preview benefit effect was found for the better deaf readers (relative to less-skilled deaf readers), although we also provide an alternative explanation for this effect. Providing evidence that Chinese deaf readers have higher efficiency when processing parafoveal semantics, the study indicates flexibility across individuals in the mechanisms underlying word recognition adapting to the inputs available in the linguistic environment. |
Keir X. X. Yong; Kishan Rajdev; Timothy J. Shakespeare; Alexander P. Leff; Sebastian J. Crutch Facilitating text reading in posterior cortical atrophy Journal Article In: Neurology, vol. 85, no. 4, pp. 339–348, 2015. @article{Yong2015, OBJECTIVE: We report (1) the quantitative investigation of text reading in posterior cortical atrophy (PCA), and (2) the effects of 2 novel software-based reading aids that result in dramatic improvements in the reading ability of patients with PCA. METHODS: Reading performance, eye movements, and fixations were assessed in patients with PCA and typical Alzheimer disease and in healthy controls (experiment 1). Two reading aids (single- and double-word) were evaluated based on the notion that reducing the spatial and oculomotor demands of text reading might support reading in PCA (experiment 2). RESULTS: Mean reading accuracy in patients with PCA was significantly worse (57%) compared with both patients with typical Alzheimer disease (98%) and healthy controls (99%); spatial aspects of passages were the primary determinants of text reading ability in PCA. Both aids led to considerable gains in reading accuracy (PCA mean reading accuracy: single-word reading aid = 96%; individual patient improvement range: 6%-270%) and self-rated measures of reading. Data suggest a greater efficiency of fixations and eye movements under the single-word reading aid in patients with PCA. CONCLUSIONS: These findings demonstrate how neurologic characterization of a neurodegenerative syndrome (PCA) and detailed cognitive analysis of an important everyday skill (reading) can combine to yield aids capable of supporting important everyday functional abilities. CLASSIFICATION OF EVIDENCE: This study provides Class III evidence that for patients with PCA, 2 software-based reading aids (single-word and double-word) improve reading accuracy. |
Jiedong Zhang; Jia Liu; Yaoda Xu Neural decoding reveals impaired face configural processing in the right fusiform face area of individuals with developmental prosopagnosia Journal Article In: Journal of Neuroscience, vol. 35, no. 4, pp. 1539–1548, 2015. @article{Zhang2015, Most of human daily social interactions rely on the ability to successfully recognize faces. Yet ∼2% of the human population suffers from face blindness without any acquired brain damage [this is also known as developmental prosopagnosia (DP) or congenital prosopagnosia]). Despite the presence of severe behavioral face recognition deficits, surprisingly, a majority of DP individuals exhibit normal face selectivity in the right fusiform face area (FFA), a key brain region involved in face configural processing. This finding, together with evidence showing impairments downstream from the right FFA in DP individuals, has led some to argue that perhaps the right FFA is largely intact in DP individuals. Using fMRI multivoxel pattern analysis, here we report the discovery of a neural impairment in the right FFA of DP individuals that may play a critical role in mediating their face-processing deficits. In seven individuals with DP, we discovered that, despite the right FFA's preference for faces and it showing decoding for the different face parts, it exhibited impaired face configural decoding and did not contain distinct neural response patterns for the intact and the scrambled face configurations. This abnormality was not present throughout the ventral visual cortex, as normal neural decoding was found in an adjacent object-processing region. To our knowledge, this is the first direct neural evidence showing impaired face configural processing in the right FFA in individuals with DP. The discovery of this neural impairment provides a new clue to our understanding of the neural basis of DP. |
Eric Avila; Josef N. Geest; Sandra Kengne Kamga; M. Claire Verhage; Opher Donchin; Maarten A. Frens Cerebellar transcranial direct current stimulation effects on saccade adaptation Journal Article In: Neural Plasticity, vol. 2015, pp. 968970, 2015. @article{Avila2015, 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. |
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 In: Journal of Neurophysiology, vol. 113, no. 9, pp. 3312–3322, 2015. @article{Bansal2015, 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. |
Hans-Joachim Bieg; Lewis L. Chuang; Heinrich H. Bülthoff; Jean-Pierre Bresciani Asymmetric saccade reaction times to smooth pursuit Journal Article In: Experimental Brain Research, vol. 233, no. 9, pp. 2527–2538, 2015. @article{Bieg2015, Before initiating a saccade to a moving target, the brain must take into account the target's eccentricity as well as its movement direction and speed. We tested how the kinematic characteristics of the target influence the time course of this oculomotor response. Participants performed a step-ramp task in which the target object stepped from a central to an eccentric position and moved at constant velocity either to the fixation position (foveopetal) or further to the periphery (foveofugal). The step size and target speed were varied. Of particular interest were trials that exhibited an initial saccade prior to a smooth pursuit eye movement. Measured saccade reaction times were longer in the foveopetal than in the foveofugal condition. In the foveopetal (but not the foveofugal) condition, the occurrence of an initial saccade, its reaction time as well as the strength of the pre-saccadic pursuit response depended on both the target's speed and the step size. A common explanation for these results may be found in the neural mechanisms that select between oculomotor response alternatives, i.e., a saccadic or smooth response. |
Hans-Joachim Bieg; Lewis L. Chuang; Heinrich H. Bülthoff; Jean-Pierre Bresciani Asymmetries in saccade reaction times to pursuit Journal Article In: Experimental Brain Research, vol. 233, no. 9, pp. 2527–2538, 2015. @article{Bieg2015a, Before initiating a saccade to a moving target, the brain must take into account the target's eccentricity as well as its movement direction and speed. We tested how the kinematic characteristics of the target influence the time course of this oculomotor response. Participants performed a step-ramp task in which the target object stepped from a central to an eccentric position and moved at constant velocity either to the fixation position (foveopetal) or further to the periphery (foveofugal). The step size and target speed were varied. Of particular interest were trials that exhibited an initial saccade prior to a smooth pursuit eye movement. Measured saccade reaction times were longer in the foveopetal than in the foveofugal condition. In the foveopetal (but not the foveofugal) condition, the occurrence of an initial saccade, its reaction time as well as the strength of the pre-saccadic pursuit response depended on both the target's speed and the step size. A common explanation for these results may be found in the neural mechanisms that select between oculomotor response alternatives, i.e., a saccadic or smooth response. |
Yoram Bonneh; Yael Adini; Uri Polat Contrast sensitivity revealed by microsaccades Journal Article In: Journal of vision, vol. 15, no. 9, pp. 1–12, 2015. @article{Bonneh2015, Microsaccades are small rapid and involuntary eye movements that occur during fixation in an apparently stochastic manner. They are known to be inhibited in response to sensory transients, with a time course that depends on the stimulus parameters and attention. However, the temporal precision of their onsets and the degree to which they can be used to assess the response of the visual system to basic stimulus parameters is currently unknown. Here we studied microsaccade response properties as a function of the contrast and spatial frequency of visual onsets. Observers (n¼ 18) viewed and silently counted 2-min sequences of Gabor patches presented briefly (100 ms) at 1 Hz. Contrast and spatial frequency were randomized in different experiments. We found that the microsaccade response time, as measured by the latency of the first microsaccade relative to stimulus onset following its release from inhibition, was sensitive to the contrast and spatial frequency of the stimulus and could be used to extract a contrast response function without the observers' response. We also found that contrast detection thresholds, measured behaviorally for different spatial frequencies, were highly and positively correlated (R = 0.87) with the microsaccade response time measured at high contrast (.4 times the threshold). These results show that different measures of microsaccade inhibition, especially the microsaccade response time, can provide accurate and involuntary measures of low-level visual properties such as contrast response and sensitivity. |
Annalisa Bosco; Markus Lappe; Patrizia Fattori Fattori Adaptation of saccades and perceived size after trans-saccadic changes of object size Journal Article In: Journal of Neuroscience, vol. 35, no. 43, pp. 14448–14456, 2015. @article{Bosco2015, When saccadic eye movements consistently fail to land on the intended target, saccade accuracy is maintained by gradually adapting the amplitude of successive saccades to the same target. Such saccadic adaptation is usually induced by systematically displacing a small visual target during the execution ofthe saccade. However, saccades are normallyperformed to extended objects. Herewe report changes in saccade amplitudewhenthe size ofa target object is systematicallychanged during a saccade. Moreover,wefind that this manipulation also affected the visual perception ofthe size ofthat object. Human subjects were tested in shortening and lengthening adaptation where they had to make saccades to targets ofdifferent sizes, which were each shortened or lengthened during saccade execution, respectively. In both experiments, a preadaptation and postadaptation phase required manually indicating the horizontal size ofeach target by grip aperture and, in a further experiment, a verbal size report. We evaluated the effect ofchange in visual perception on saccade and on the two modalities ofjudgment.Weobserved that (1) saccadic adaptation can be induced by modifying target object size and (2) this gradual change in saccade amplitude in the direction of the object size change evokes a concomitant change in perceived object size. These findings suggest that size is a relevant signal for saccadic system and its trans-saccadic manipulation entails considerable changes at multiple levels ofsensorimotor performance. |
Antonia F. Ten Brink; Tanja C. W. Nijboer; Douwe P. Bergsma; Jason J. S. Barton; Stefan Van der Stigchel Lack of multisensory integration in hemianopia: No influence of visual stimuli on aurally guided saccades to the blind hemifield Journal Article In: PLoS ONE, vol. 10, no. 4, pp. e0122054, 2015. @article{Brink2015, In patients with visual hemifield defects residual visual functions may be present, a phenomenon called blindsight. The superior colliculus (SC) is part of the spared pathway that is considered to be responsible for this phenomenon. Given that the SC processes input from different modalities and is involved in the programming of saccadic eye movements, the aim of the present study was to examine whether multimodal integration can modulate oculomotor competition in the damaged hemifield. We conducted two experiments with eight patients who had visual field defects due to lesions that affected the retinogeniculate pathway but spared the retinotectal direct SC pathway. They had to make saccades to an auditory target that was presented alone or in combination with a visual stimulus. The visual stimulus could either be spatially coincident with the auditory target (possibly enhancing the auditory target signal), or spatially disparate to the auditory target (possibly competing with the auditory tar-get signal). For each patient we compared the saccade endpoint deviation in these two bi-modal conditions with the endpoint deviation in the unimodal condition (auditory target alone). In all seven hemianopic patients, saccade accuracy was affected only by visual stimuli in the intact, but not in the blind visual field. In one patient with a more limited quadrantano-pia, a facilitation effect of the spatially coincident visual stimulus was observed. We conclude that our results show that multisensory integration is infrequent in the blind field of patients with hemianopia. |