EyeLink 临床和动眼神经眼球追踪出版物
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!
2012 |
Eugene McSorley; Rachel McCloy; Clare Lyne The spatial impact of visual distractors on saccade latency Journal Article In: Vision Research, vol. 60, pp. 61–72, 2012. @article{McSorley2012, Remote transient changes in the environment, such as the onset of visual distractors, impact on the execution of target directed saccadic eye movements. Studies that have examined the latency of the saccade response have shown conflicting results. When there was an element of target selection, saccade latency increased as the distance between distractor and target increased. In contrast, when target selection is minimized by restricting the target to appear on one axis position, latency has been found to be slowest when the distractor is shown at fixation and reduces as it moves away from this position, rather than from the target. Here we report four experiments examining saccade latency as target and distractor positions are varied. We find support for both a dependence of saccade latency on distractor distance from target and from fixation: saccade latency was longer when distractor is shown close to fixation and even longer still when shown in an opposite location (180°) to the target. We suggest that this is due to inhibitory interactions between the distractor, fixation and the target interfering with fixation disengagement and target selection. |
David Melcher; Alessio Fracasso Remapping of the line motion illusion across eye movements Journal Article In: Experimental Brain Research, vol. 218, no. 4, pp. 503–514, 2012. @article{Melcher2012, Although motion processing in the brain has been classically studied in terms of retinotopically defined receptive fields, recent evidence suggests that motion perception can occur in a spatiotopic reference frame. We investigated the underlying mechanisms of spatiotopic motion perception by examining the role of saccade metrics as well as the capacity of trans-saccadic motion. To this end, we used the line motion illusion (LMI), in which a straight line briefly shown after a high contrast stimulus (inducer) is perceived as expanding away from the inducer position. This illusion provides an interesting test of spatiotopic motion because the neural correlates of this phenomenon have been found early in the visual cortex and the effect does not require focused attention. We measured the strength of LMI both with stable fixation and when participants were asked to perform a 10° saccade during the blank ISI between the inducer and the line. A strong motion illusion was found across saccades in spatiotopic coordinates. When the inducer was presented near in time to the saccade cue, saccadic latencies were longer, saccade amplitudes were shorter, and the strength of reported LMI was consistently reduced. We also measured the capacity of the trans-saccadic LMI by varying the number of inducers. In contrast to a visual-spatial memory task, we found that the LMI was largely eliminated by saccades when two or more inducers were displayed. Together, these results suggest that motion perceived in non-retinotopic coordinates depends on an active, saccade-dependent remapping process with a strictly limited capacity. |
Muriel T. N. Panouillères; Sebastiaan F. W. Neggers; Tjerk P. Gutteling; Roméo Salemme; Stefan Stigchel; Josef N. Geest; Maarten A. Frens; Denis Pélisson Transcranial magnetic stimulation and motor plasticity in human lateral cerebellum: Dual effect on saccadic adaptation Journal Article In: Human Brain Mapping, vol. 33, no. 7, pp. 1512–1525, 2012. @article{Panouilleres2012, The cerebellum is a key area for movement control and sensory-motor plasticity. Its medial part is considered as the exclusive cerebellar center controlling the accuracy and adaptive calibration of saccadic eye movements. However, the contribution of other zones situated in its lateral part is unknown. We addressed this question in healthy adult volunteers by using magnetic resonance imaging (MRI)-guided transcranial magnetic stimulation (TMS). The double-step target paradigm was used to adaptively lengthen or shorten saccades. TMS pulses over the right hemisphere of the cerebellum were delivered at 0, 30, or 60 ms after saccade detection in separate recording sessions. The effects on saccadic adaptation were assessed relative to a fourth session where TMS was applied to Vertex as a control site. First, TMS applied upon saccade detection before the adaptation phase reduced saccade accuracy. Second, TMS applied during the adaptation phase had a dual effect on saccadic plasticity: adaptation after-effects revealed a potentiation of the adaptive lengthening and a depression of the adaptive shortening of saccades. For the first time, we demonstrate that TMS on lateral cerebellum can influence plasticity mechanisms underlying motor performance. These findings also provide the first evidence that the human cerebellar hemispheres are involved in the control of saccade accuracy and in saccadic adaptation, with possibly different neuronal populations concerned in adaptive lengthening and shortening. Overall, these results require a reappraisal of current models of cerebellar contribution to oculomotor plasticity. |
Muriel T. N. Panouillères; Roméo Salemme; Christian Urquizar; Denis Pélisson Effect of saccadic adaptation on sequences of saccades Journal Article In: Journal of Eye Movement Research, vol. 5, no. 1, pp. 1–13, 2012. @article{Panouilleres2012a, Accuracy of saccadic eye movements is maintained thanks to adaptation mechanisms. The adaptive lengthening and shortening of reactive and voluntary saccades rely on partially separate neural substrates. Although in daily-life we mostly perform sequences of saccades, the effect of saccadic adaptation has been mainly evaluated on single saccades. Here, sequences of two saccades were recorded before and after adaptation of rightward saccades. In 4 separate sessions, reactive and voluntary saccades were adaptively shortened or lengthened. We found that the second saccade of the sequence always remained accurate and compensated for the adaptive changes of the first rightward saccade size. This finding suggests that adaptation loci are upstream of the site where the efference copy involved in sequence planning originates. |
Sara A. Beedie; Philip J. Benson; Ina Giegling; Dan Rujescu; David M. St. Clair Smooth pursuit and visual scanpaths: Independence of two candidate oculomotor risk markers for schizophrenia Journal Article In: The World Journal of Biological Psychiatry, vol. 13, no. 3, pp. 200–210, 2012. @article{Beedie2012, Objectives. Smooth pursuit and visual scanpath deficits are candidate trait markers for schizophrenia. It is not clear whether eye tracking dysfunction (ETD) and atypical scanpath behaviour are the product of the same underlying neurobiological processes. We have examined co-occurrence of ETD and scanpath disturbance in individuals with schizophrenia and healthy volunteers. Methods. Eye movements of individuals with schizophrenia (N = 96) and non-clinical age-matched comparison participants (N = 100) were recorded using non-invasive infrared oculography during smooth pursuit in both predictable (horizontal sinusoid) and less predictable (Lissajous sinusoid) conditions and a free viewing scanpath task. Results. Individuals with schizophrenia demonstrated scanning deficits in both tasks. There was no association between performance measures of smooth pursuit and scene scanpaths in patient or control groups. Odds ratios comparing the likelihood of scanpath dysfunction when ETD was present, and the likelihood of finding scanpath dysfunction when ETD was absent were not significant in patients or controls in either pursuit variant, suggesting that ETD and scanpath dysfunction are independent anomalies in schizophrenia. Conclusion. ETD and scanpath disturbance appear to reflect independent oculomotor or neurocognitive deficits in schizophrenia. Each task may confer unique information about the pathophysiology of psychosis. © 2012 Informa Healthcare. |
Artem V. Belopolsky; Jan Theeuwes Updating the premotor theory: The allocation of attention is not always accompanied by saccade preparation Journal Article In: Journal of Experimental Psychology: Human Perception and Performance, vol. 38, no. 4, pp. 902–914, 2012. @article{Belopolsky2012, There is an ongoing controversy regarding the relationship between covert attention and saccadic eye movements. While there is quite some evidence that the preparation of a saccade is obligatory preceded by a shift of covert attention, the reverse is not clear: Is allocation of attention always accompanied by saccade preparation? Recently, a shifting and maintenance account was proposed suggesting that shifting and maintenance components of covert attention differ in their relation to the oculomotor system. Specifically, it was argued that a shift of covert attention is always accompanied by activation of the oculomotor program, while maintaining covert attention at a location can be accompanied either by activation or suppression of oculomotor program, depending on the probability of executing an eye movement to the attended location. In the present study we tested whether there is such an obligatory coupling between shifting of attention and saccade preparation and how quickly saccade preparation gets suppressed. The results showed that attention shifting was always accompanied by saccade preparation whenever covert attention had to be shifted during visual search, as well as in response to exogenous or endogenous cues. However, for the endogenous cues the saccade program to the attended location was suppressed very soon after the attention shift was completed. The current findings support the shifting and maintenance account and indicate that the premotor theory needs to be updated to include a shifting and maintenance component for the cases in which covert shifts of attention are made without the intention to execute a saccade. |
Mario Bettenbühl; Marco Rusconi; Ralf Engbert; Matthias Holschneider Bayesian selection of Markov Models for symbol sequences: Application to microsaccadic eye movements Journal Article In: PLoS ONE, vol. 7, no. 9, pp. e43388, 2012. @article{Bettenbuehl2012, Complex biological dynamics often generate sequences of discrete events which can be described as a Markov process. The order of the underlying Markovian stochastic process is fundamental for characterizing statistical dependencies within sequences. As an example for this class of biological systems, we investigate the Markov order of sequences of microsaccadic eye movements from human observers. We calculate the integrated likelihood of a given sequence for various orders of the Markov process and use this in a Bayesian framework for statistical inference on the Markov order. Our analysis shows that data from most participants are best explained by a first-order Markov process. This is compatible with recent findings of a statistical coupling of subsequent microsaccade orientations. Our method might prove to be useful for a broad class of biological systems. |
Hans-Joachim Bieg; Jean-Pierre Bresciani; Heinrich H. Bülthoff; Lewis L. Chuang Looking for discriminating Is dDifferent from looking for looking's sake Journal Article In: PLoS ONE, vol. 7, no. 9, pp. e45445, 2012. @article{Bieg2012, Recent studies provide evidence for task-specific influences on saccadic eye movements. For instance, saccades exhibit higher peak velocity when the task requires coordinating eye and hand movements. The current study shows that the need to process task-relevant visual information at the saccade endpoint can be, in itself, sufficient to cause such effects. In this study, participants performed a visual discrimination task which required a saccade for successful completion. We compared the characteristics of these task-related saccades to those of classical target-elicited saccades, which required participants to fixate a visual target without performing a discrimination task. The results show that task-related saccades are faster and initiated earlier than target-elicited saccades. Differences between both saccade types are also noted in their saccade reaction time distributions and their main sequences, i.e., the relationship between saccade velocity, duration, and amplitude. |
Richard S. Bogartz; Adrian Staub Gaze step distributions reflect fixations and saccades: A comment on Stephen and Mirman (2010) Journal Article In: Cognition, vol. 123, no. 2, pp. 325–334, 2012. @article{Bogartz2012, In three experimental tasks Stephen and Mirman (2010) measured gaze steps, the distance in pixels between gaze positions on successive samples from an eyetracker. They argued that the distribution of gaze steps is best fit by the lognormal distribution, and based on this analysis they concluded that interactive cognitive processes underlie eye movement control in these tasks. The present comment argues that the gaze step distribution is predictable based on the fact that the eyes alternate between a fixation state in which gaze is steady and a saccade state in which gaze position changes rapidly. By fitting a simple mixture model to Stephen and Mirman's gaze step data we reveal a fixation distribution and a saccade distribution. This mixture model captures the shape of the gaze step distribution in detail, unlike the lognormal model, and provides a better quantitative fit to the data. We conclude that the gaze step distribution does not directly suggest processing interaction, and we emphasize some important limits on the utility of fitting theoretical distributions to data. |
Davide Bottari; Matteo Valsecchi; Francesco Pavani Prominent reflexive eye-movement orienting associated with deafness Journal Article In: Cognitive Neuroscience, vol. 3, no. 1, pp. 8–13, 2012. @article{Bottari2012, Profound deafness affects orienting of visual attention. Until now, research focused exclusively on covert attentional orienting, neglecting whether overt oculomotor behavior may also change in deaf people. Here we used the pro- and anti-saccade task to examine the relative contribution of reflexive and voluntary eye-movement control in profoundly deaf and hearing individuals. We observed a behavioral facilitation in reflexive compared to voluntary eye movements, indexed by faster saccade latencies and smaller error rates in pro- than anti-saccade trials, which was substantially larger in deaf than hearing participants. This provides the first evidence of plastic changes related to deafness in overt oculomotor behavior, and constitutes an ecologically relevant parallel to the modulations attributed to deafness in covert attention orienting. Our findings also have implications for designers of real and virtual environments for deaf people and reveal that experiments on deaf visual abilities must not ignore the prominent reflexive eye-movement orienting in this sensory-deprived population. |
Antimo Buonocore; Robert D. McIntosh Modulation of saccadic inhibition by distractor size and location Journal Article In: Vision Research, vol. 69, pp. 32–41, 2012. @article{Buonocore2012, Distractors presented contralateral to a visual target inhibit the generation of saccades within a precise temporal window (Buonocore & McIntosh, 2008; Reingold & Stampe, 2002; Walker, Kentridge, & Findlay, 1995). The greatest 'dip' of saccadic inhibition typically occurs at about 90. ms after distractor onset, with a subsequent recovery period showing an elevated frequency of saccades. It is not yet known how the spatial properties of the distractor stimulus influence the saccadic inhibition signature. To study this, we manipulated the size and the field of presentation of the distractor in four experiments. Experiment 1 demonstrated that the size of a distractor in the contralateral field is logarithmically related to the magnitude of the saccadic inhibition dip. This implies that the probability of a planned saccade being inhibited increases logarithmically with the size of the distractor. Experiment 2 showed a qualitatively similar but more pronounced effect of size for distractors in the ipsilateral field. Experiment 3 compared the effects of contralateral and ipsilateral distractors directly using a within-subjects design, confirming the more pronounced impact of ipsilateral distractors. Experiment 4 replicated the more pronounced effect of ipsilateral distractors in a task in which target side was unpredictable, confirming that the effect does not result merely from participants preparing in advance to ignore events on one side. We suggest that participants are more able to resist contralateral distraction during target selection, as they can more effectively withdraw attention from locations remote from the target than from locations close to it. |
Amanda F. Moates; Elena I. Ivleva; Hugh B. O'Neill; Nithin Krishna; C. Munro Cullum; Gunvant K. Thaker; Carol A. Tamminga Predictive pursuit association with deficits in working memory in psychosis Journal Article In: Biological Psychiatry, vol. 72, no. 9, pp. 752–757, 2012. @article{Moates2012, Background: Deficits in smooth pursuit eye movements are an established phenotype for schizophrenia (SZ) and are being investigated as a potential liability marker for bipolar disorder. Although the molecular determinants of this deficit are still unclear, research has verified deficits in predictive pursuit mechanisms in SZ. Because predictive pursuit might depend on the working memory system, we have hypothesized a relationship between the two in healthy control subjects (HC) and SZ and here examine whether it extends to psychotic bipolar disorder (BDP). Methods: Volunteers with SZ (n = 38), BDP (n = 31), and HC (n = 32) performed a novel eye movement task to assess predictive pursuit as well as a standard visuospatial measure of working memory. Results: Individuals with SZ and BDP both showed reduced predictive pursuit gain compared with HC (p <.05). Moreover, each patient group showed worse performance in visuospatial working memory compared with control subjects (p <.05). A strong correlation (r =.53 |
Antje Nuthmann; John M. Henderson Using CRISP to model global characteristics of fixation durations in scene viewing and reading with a common mechanism Journal Article In: Visual Cognition, vol. 20, no. 4-5, pp. 457–494, 2012. @article{Nuthmann2012, Fixation durations vary when we read text or inspect a natural scene. Past studies suggest that this variability is controlled by the visual input available within the current fixation. The present study directly compared the control of fixation durations in reading and scene viewing in a common experimental paradigm, and attempted to account for the control of these durations within a common modelling framework using the CRISP architecture (Nuthmann, Smith, Engbert, & Henderson, 2010). In the experimental paradigm, a stimulus onset delay paradigm was used. Avisual mask was presented at the beginning of critical fixations, which delayed the onset of the text or scene, and the length of the delay was varied. Irrespective of task, two populations of fixation durations were observed. One population of fixations was under the direct control of the current stimulus, increasing in duration as delay increased. A second population of fixation durations was relatively constant across delay. Additional task-specific quantitative differ- ences in the adjustment of fixation durations were found. The pattern of mixed control of fixation durations obtained for scene viewing has been previously simulated with the CRISP model of fixation durations. In the present work, the model's generality was tested by applying its architecture to the text reading data, with task-specific influences realized by different parameter settings. The results of the numerical simulations suggest that global characteristics of fixation durations in scene viewing and reading can be explained by a common mechanism. |
Jorge Otero-Millan; Stephen L. Macknik; Susana Martinez-Conde Microsaccades and blinks trigger illusory rotation in the "rotating snakes" illusion Journal Article In: Journal of Neuroscience, vol. 32, no. 17, pp. 6043–6051, 2012. @article{OteroMillan2012, Certain repetitive arrangements of luminance gradients elicit the perception of strong illusory motion. Among them, the "Rotating Snakes Illusion" has generated a large amount of interest in the visual neurosciences, as well as in the public. Prior evidence indicates that the Rotating Snakes illusion depends critically on eye movements, yet the specific eye movement types involved and their associated neural mechanisms remain controversial. According to recent reports, slow ocular drift–a nonsaccadic type of fixational eye movement–drives the illusion, whereas microsaccades produced during attempted fixation fail to do so. Here, we asked human subjects to indicate the presence or absence of rotation during the observation of the illusion while we simultaneously recorded their eye movements with high precision. We found a strong quantitative link between microsaccade and blink production and illusory rotation. These results suggest that transient oculomotor events such as microsaccades, saccades, and blinks, rather than continuous drift, act to trigger the illusory motion in the Rotating Snakes illusion. |
Ava-Ann Allman; Ulrich Ettinger; Ridha Joober; Gillian A. O'Driscoll Effects of methylphenidate on basic and higher-order oculomotor functions Journal Article In: Journal of Psychopharmacology, vol. 26, no. 11, pp. 1471–1479, 2012. @article{Allman2012, Eye movements are sensitive indicators of pharmacological effects on sensorimotor and cognitive processing. Methylphenidate (MPH) is one of the most prescribed medications in psychiatry. It is increasingly used as a cognitive enhancer by healthy individuals. However, little is known of its effect on healthy cognition. Here we used oculomotor tests to evaluate the effects of MPH on basic oculomotor and executive functions. Twenty-nine males were given 20mg of MPH orally in a double-blind placebo-controlled crossover design. Participants performed visually-guided saccades, sinusoidal smooth pursuit, predictive saccades and antisaccades one hour post-capsule administration. Heart rate and blood pressure were assessed prior to capsule administration, and again before and after task performance. Visually-guided saccade latency decreased with MPH (p<0.004). Smooth pursuit gain increased on MPH (p<0.001) and number of saccades during pursuit decreased (p<0.001). Proportion of predictive saccades increased on MPH (p<0.004), specifically in conditions with predictable timing. Peak velocity of predictive saccades increased with MPH (p<0.01). Antisaccade errors and latency were unaffected. Physiological variables were also unaffected. The effects on visually-guided saccade latency and peak velocity are consistent with MPH effects on dopamine in basal ganglia. The improvements in predictive saccade conditions and smooth pursuit suggest effects on timing functions. |
Gary Feng Is there a common control mechanism for anti-saccades and reading eye movements? Evidence from distributional analyses Journal Article In: Vision Research, vol. 57, pp. 35–50, 2012. @article{Feng2012, In the saccadic literature, the voluntary control of eye movement involves inhibiting automatic saccadic plans. In contrast, the dominant view in reading is that linguistic processes trigger saccade planning. The present study explores the possibility of a common control mechanism, in which cognitively driven responses compete to inhibit automatic, perceptually driven saccade plans. A probabilistic model is developed to account for empirical distributions of saccadic response time in anti-saccade tasks (Studies 1 and 2) and fixation duration in reading and reading-like tasks (Studies 3 and 4). In all cases the distributions can be decomposed into a perceptually based component and a component sensitive to cognitive demands. Parametric similarities among the models strongly suggest a shared cognitive control mechanism between reading and other voluntary saccadic tasks. |
Josselin Gautier; O. Le Meur A time-dependent saliency model combining center and depth biases for 2D and 3D viewing conditions Journal Article In: Cognitive Computation, vol. 4, no. 2, pp. 141–156, 2012. @article{Gautier2012, The role of the binocular disparity in the deployment of visual attention is examined in this paper. To address this point, we compared eye tracking data recorded while observers viewed natural images in 2D and 3D conditions. The influence of disparity on saliency, center and depth biases is first studied. Results show that visual exploration is affected by the introduction of the binocular disparity. In particular, participants tend to look first at closer areas in 3D condition and then direct their gaze to more widespread locations. Beside this behavioral analysis, we assess the extent to which state-of-the-art models of bottom-up visual attention predict where observers looked at in both viewing conditions. To improve their ability to predict salient regions, low-level features as well as higher-level foreground/background cues are examined. Results indicate that, consecutively to initial centering response, the foreground feature plays an active role in the early but also middle instants of attention deployments. Importantly, this influence is more pronounced in stereoscopic conditions. It supports the notion of a quasi-instantaneous bottom-up saliency modulated by higher figure/ground processing. Beyond depth information itself, the foreground cue might constitute an early process of “selection for action”. Finally, we propose a time-dependent computational model to predict saliency on still pictures. The proposed approach combines low-level visual features, center and depth biases. Its performance outperforms state-of-the-art models of bottom-up attention. |
Marc Grosjean; Gerhard Rinkenauer; Stephanie Jainta Where do the eyes really go in the hollow-face illusion? Journal Article In: PLoS ONE, vol. 7, no. 9, pp. e44706, 2012. @article{Grosjean2012, The hollow-face illusion refers to the finding that people typically perceive a concave (hollow) mask as being convex, despite the presence of binocular disparity cues that indicate the contrary. Unlike other illusions of depth, recent research has suggested that the eyes tend to converge at perceived, rather than actual, depths. However, technical and methodological limitations prevented one from knowing whether disparity cues may still have influenced vergence. In the current study, we presented participants with virtual normal or hollow masks and asked them to fixate the tip of the face's nose until they had indicated whether they perceived it as pointing towards or away from them. The results showed that the direction of vergence was indeed determined by perceived depth, although vergence responses were both somewhat delayed and of smaller amplitude (by a factor of about 0.5) for concave than convex masks. These findings demonstrate how perceived depth can override disparity cues when it comes to vergence, albeit not entirely. |
Thérèse Collins Probability of seeing increases saccadic readiness Journal Article In: PLoS ONE, vol. 7, no. 11, pp. e49454, 2012. @article{Collins2012, Associating movement directions or endpoints with monetary rewards or costs influences movement parameters in humans, and associating movement directions or endpoints with food reward influences movement parameters in non-human primates. Rewarded movements are facilitated relative to non-rewarded movements. The present study examined to what extent successful foveation facilitated saccadic eye movement behavior, with the hypothesis that foveation may constitute an informational reward. Human adults performed saccades to peripheral targets that either remained visible after saccade completion or were extinguished, preventing visual feedback. Saccades to targets that were systematically extinguished were slower and easier to inhibit than saccades to targets that afforded successful foveation, and this effect was modulated by the probability of successful foveation. These results suggest that successful foveation facilitates behavior, and that obtaining the expected sensory consequences of a saccadic eye movement may serve as a reward for the oculomotor system. |
Thérèse Collins; Josh Wallman The relative importance of retinal error and prediction in saccadic adaptation Journal Article In: Journal of Neurophysiology, vol. 107, no. 12, pp. 3342–3348, 2012. @article{Collins2012a, When saccades systematically miss their visual target, their amplitude adjusts, causing the position errors to be progressively reduced. Conventionally, this adaptation is viewed as driven by retinal error (the distance between primary saccade endpoint and visual target). Recent work suggests that the oculomotor system is informed about where the eye lands; thus not all "retinal error" is unexpected. The present study compared two error signals that may drive saccade adaptation: retinal error and prediction error (the difference between predicted and actual postsaccadic images). Subjects made saccades to a visual target in two successive sessions. In the first session, the target was extinguished during saccade execution if the amplitude was smaller (or, in other experiments, greater) than the running median, thereby modifying the average retinal error subjects experienced without moving the target during the saccade as in conventional adaptation paradigms. In the second session, targets were extinguished at the start of saccades and turned back on at a position that reproduced the trial-by-trial retinal error recorded in the first session. Despite the retinal error in the first and second sessions having been identical, adaptation was severalfold greater in the second session, when the predicted target position had been changed. These results argue that the eye knows where it lands and where it expects the target to be, and that deviations from this prediction drive saccade adaptation more strongly than retinal error alone. |
Sébastien Coppe; Jean-Jacques Orban de Xivry; Demet Yuksel; Adrian Ivanoiu; Philippe Lefevre Dramatic impairment of prediction due to frontal lobe degeneration Journal Article In: Journal of Neurophysiology, vol. 108, no. 11, pp. 2957–2966, 2012. @article{Coppe2012, Prediction is essential for motor function in everyday life. For instance, predictive mechanisms improve the perception of a moving target by increasing eye speed anticipatively, thus reducing motion blur on the retina. Subregions of the frontal lobes play a key role in eye movements in general and in smooth pursuit in particular, but their precise function is not firmly established. Here, the role of frontal lobes in the timing of predictive action is demonstrated by studying predictive smooth pursuit during transient blanking of a moving target in mild frontotemporal lobar degeneration (FTLD) and Alzheimer's disease (AD) patients. While control subjects and AD patients predictively reaccelerated their eyes before the predicted time of target reappearance, FTLD patients did not. The difference was so dramatic (classification accuracy ⬎90%) that it could even lead to the definition of a new biomarker. In contrast, anticipatory eye movements triggered by the disappearance of the fixation point were still present before target motion onset in FTLD patients and visually guided pursuit was normal in both patient groups compared with controls. Therefore, FTLD patients were only impaired when the predicted timing of an external event was required to elicit an action. These results argue in favor of a role of the frontal lobes in predictive movement timing. |
Kurt Debono; Alexander C. Schütz; Karl R. Gegenfurtner Illusory bending of pursuit target Journal Article In: Vision Research, vol. 57, pp. 51–60, 2012. @article{Debono2012, To pursue a small target moving in front of a drifting background, motion vectors from the target need to be integrated and segmented from those belonging to the background. Smooth pursuit eye movements typically integrate target and background directions initially and after some time shift towards the veridical target direction. The perceived target direction on the other hand is generally stable over time: the target is perceived to move in the same direction as long as the motion information maintains the same properties over time. If illusory target motion is observed, this tends to be shifted away from the background. Here we investigated how initial motion integration and segmentation of such stimuli are modulated by direction cues. We presented a small pursuit target moving along a straight path, in front of a background moving in a different direction. Without a direction cue, initial pursuit was biased towards the background direction before shifting towards the veridical target direction. The target's perceived direction on the other hand was near veridical. A cue in the background direction increased initial pursuit integration but also caused perception to behave in a similar way: the target initially had an illusory motion component in the background direction and after about 200 ms it was perceived to curve towards its veridical direction. This illusion shows that during the initial process of segmenting the direction of a pursuit target from irrelevant background motion, both pursuit and perception can be erroneously influenced by a direction cue and integrate the cued background motion. Both modalities corrected this initial integration error as more information about the target became available. |
Adele Diederich; Annette Schomburg; Hans Colonius Saccadic reaction times to audiovisual stimuli show effects of oscillatory phase reset Journal Article In: PLoS ONE, vol. 7, no. 10, pp. e44910, 2012. @article{Diederich2012, Initiating an eye movement towards a suddenly appearing visual target is faster when an accessory auditory stimulus occurs in close spatiotemporal vicinity. Such facilitation of saccadic reaction time (SRT) is well-documented, but the exact neural mechanisms underlying the crossmodal effect remain to be elucidated. From EEG/MEG studies it has been hypothesized that coupled oscillatory activity in primary sensory cortices regulates multisensory processing. Specifically, it is assumed that the phase of an ongoing neural oscillation is shifted due to the occurrence of a sensory stimulus so that, across trials, phase values become highly consistent (phase reset). If one can identify the phase an oscillation is reset to, it is possible to predict when temporal windows of high and low excitability will occur. However, in behavioral experiments the pre-stimulus phase will be different on successive repetitions of the experimental trial, and average performance over many trials will show no signs of the modulation. Here we circumvent this problem by repeatedly presenting an auditory accessory stimulus followed by a visual target stimulus with a temporal delay varied in steps of 2 ms. Performing a discrete time series analysis on SRT as a function of the delay, we provide statistical evidence for the existence of distinct peak spectral components in the power spectrum. These frequencies, although varying across participants, fall within the beta and gamma range (20 to 40 Hz) of neural oscillatory activity observed in neurophysiological studies of multisensory integration. Some evidence for high-theta/alpha activity was found as well. Our results are consistent with the phase reset hypothesis and demonstrate that it is amenable to testing by purely psychophysical methods. Thus, any theory of multisensory processes that connects specific brain states with patterns of saccadic responses should be able to account for traces of oscillatory activity in observable behavior. |
Jean Duchesne; Vincent Bouvier; Julien Guillemé; Olivier A. Coubard Maxwellian eye fixation during natural scene perception Journal Article In: The Scientific World Journal, pp. 1–12, 2012. @article{Duchesne2012, When we explore a visual scene, our eyes make saccades to jump rapidly from one area to another and fixate regions of interest to extract useful information. While the role of fixation eye movements in vision has been widely studied, their random nature has been a hitherto neglected issue. Here we conducted two experiments to examine the Maxwellian nature of eye movements during fixation. In Experiment 1, eight participants were asked to perform free viewing of natural scenes displayed on a computer screen while their eye movements were recorded. For each participant, the probability density function (PDF) of eye movement amplitude during fixation obeyed the law established by Maxwell for describing molecule velocity in gas. Only the mean amplitude of eye movements varied with expertise, which was lower in experts than novice participants. In Experiment 2, two participants underwent fixed time, free viewing of natural scenes and of their scrambled version while their eye movements were recorded. Again, the PDF of eye movement amplitude during fixation obeyed Maxwell’s law for each participant and for each scene condition (normal or scrambled). The results suggest that eye fixation during natural scene perception describes a random motion regardless of top-down or of bottom-up processes. |
Kelly S. Wild; Ellen Poliakoff; Andrew Jerrison; Emma Gowen Goal-directed and goal-less imitation in autism spectrum disorder Journal Article In: Journal of Autism and Developmental Disorders, vol. 42, no. 8, pp. 1739–1749, 2012. @article{Wild2012, To investigate how people with Autism are affected by the presence of goals during imitation, we conducted a study to measure movement kinematics and eye movements during the imitation of goal-directed and goal-less hand movements. Our results showed that a control group imitated changes in movement kinematics and increased the level that they tracked the hand with their eyes, in the goal-less compared to goal-direction condition. In contrast, the ASD group exhibited more goal-directed eye movements, and failed to modulate the observed movement kinematics successfully in either condition. These results increase the evidence for impaired goal-less imitation in ASD, and suggest that there is a reliance on goal-directed strategies for imitation in ASD, even in the absence of visual goals. |
C. Ellie Wilson; Romina Palermo; Jon Brock Visual scan paths and recognition of facial identity in autism spectrum disorder and typical development Journal Article In: PLoS ONE, vol. 7, no. 5, pp. e37681, 2012. @article{Wilson2012, Background: Previous research suggests that many individuals with autism spectrum disorder (ASD) have impaired facial identity recognition, and also exhibit abnormal visual scanning of faces. Here, two hypotheses accounting for an association between these observations were tested: i) better facial identity recognition is associated with increased gaze time on the Eye region; ii) better facial identity recognition is associated with increased eye-movements around the face. Methodology andPrincipalFindings: Eye-movements of 11 children with ASD and 11 age-matched typically developing (TD) controls were recorded whilst they viewed a series of faces, and then completed a two alternative forced-choice recognition memory test for the faces. Scores on the memory task were standardized according to age. In both groups, there was no evidence of an association between the proportion of time spent looking at the Eye region of faces and age- standardized recognition performance, thus the first hypothesis was rejected. However, the ‘Dynamic Scanning Index' – which was incremented each time the participant saccaded into and out of one of the core-feature interest areas – was strongly associated with age-standardized face recognition scores in both groups, even after controlling for various other potential predictors of performance. Conclusions andSignificance: In support of the second hypothesis, results suggested that increased saccading between core-features was associated with more accurate face recognition ability, both in typical development and ASD. Causal directions of this relationship remain undetermined. |
Luminita Tarita-Nistor; Michael H. Brent; Martin J. Steinbach; Esther G. González Fixation patterns in maculopathy: From binocular to monocular viewing Journal Article In: Optometry and Vision Science, vol. 89, no. 3, pp. 277–287, 2012. @article{TaritaNistor2012, PURPOSE: The goal of this study was to explore binocular coordination during fixation in patients with age-related macular degeneration (AMD) and to investigate whether there is a shift in eye position when the viewing condition changes from binocular to monocular. METHODS: Sixteen people with normal vision and 12 patients with AMD were asked to look at a 3 deg fixation target with both eyes and with each eye individually while the fellow eye was covered by an infrared filter. Fixational eye movements were recorded for both eyes with an EyeLink eye-tracker in all conditions. The shift in eye position at the end of every fixation period was calculated for each eye. RESULTS: All people with normal vision as well as the majority of patients had good binocular coordination during fixation in the binocular viewing condition. When the viewing condition changed from binocular to monocular, three patients (25%) had atypical shifts in their eye position. The shift was related to (1) loss of fixational control when the better eye was covered and the worse eye viewed the target or (2) a slow drift of the viewing eye that was associated with a large phoria in the covered eye. CONCLUSIONS: Patients with AMD have good binocular ocular motor coordination during fixation. A change in viewing condition from binocular to monocular can lead to disturbances in ocular motor control for some patients, especially in the worse eye. |
Stefan Van der Stigchel; Tanja C. W. Nijboer; D. P. Bergsma; Jason J. S. Barton; Chris L. E. Paffen Measuring palinopsia: Characteristics of a persevering visual sensation from cerebral pathology Journal Article In: Journal of the Neurological Sciences, vol. 316, no. 1-2, pp. 184–188, 2012. @article{VanderStigchel2012b, Palinopsia is an abnormal perseverative visual phenomenon, whose relation to normal afterimages is unknown. We measured palinoptic positive visual afterimages in a patient with a cerebral lesion. Positive afterimages were confined to the left inferior quadrant, which allowed a comparison between afterimages in the intact and the affected part of his visual field. Results showed that negative afterimages in the affected quadrant were no different from those in the unaffected quadrant. The positive afterimage in his affected field, however, differed both qualitatively and quantitatively from normal afterimages, being weaker but much more persistent, and displaced from the location of the inducing stimulus. These findings reveal distinctions between pathological afterimages of cerebral origin and physiological afterimages of retinal origin. |
Stefan Van der Stigchel; M. Koningsbruggen; Tanja C. W. Nijboer; Alexandra List; Robert D. Rafal The role of the frontal eye fields in the oculomotor inhibition of reflexive saccades: Evidence from lesion patients Journal Article In: Neuropsychologia, vol. 50, no. 1, pp. 198–203, 2012. @article{VanderStigchel2012, The current study investigated the role of the frontal eye fields (FEF) in the suppression of an unwanted eye movement ('oculomotor inhibition'). Oculomotor inhibition has generally been investigated using the antisaccade task, in which an eye movement to a task-relevant onset must be inhibited. Various lines of research have suggested that successful inhibition in the antisaccade task relies heavily on the FEF. Here, we tested whether the FEF are also involved in the oculomotor inhibition of reflexive saccades. To this end, we used the oculomotor capture task in which the to-be-inhibited element is task-irrelevant. Performance of four patients with lesions to the FEF was measured on both the antisaccade and oculomotor capture task. In both tasks, the majority of the patients made more erroneous eye movements to contralesional elements than to ipsilesional elements. One patient showed no deficits in the antisaccade task, which could be explained by the developmental origin of his lesion. While we confirm the role of the FEF in the inhibition of task-relevant elements, the current study also reveals that the FEF play a crucial role in the oculomotor inhibition of task-irrelevant elements. |
Jason Rupp; Mario Dzemidzic; Tanya Blekher; John West; Siu L. Hui; Joanne Wojcieszek; Andrew J. Saykin; David A. Kareken; Tatiana M. Foroud Comparison of vertical and horizontal saccade measures and their relation to gray matter changes in premanifest and manifest Huntington disease Journal Article In: Journal of Neurology, vol. 259, no. 2, pp. 267–276, 2012. @article{Rupp2012, Saccades are a potentially important biomarker of Huntington disease (HD) progression, as saccadic abnormalities can be detected both cross-sectionally and longitudinally. Although vertical saccadic impairment was reported decades ago, recent studies have focused on horizontal saccades. This study investigated antisaccade (AS) and memory guided saccade (MG) impairment in both the horizontal and vertical directions in individuals with the disease-causing CAG expansion (CAG+; n = 74), using those without the expansion (CAG-; n = 47) as controls. Percentage of errors, latency, and variability of latency were used to measure saccadic performance. We evaluated the benefits of measuring saccades in both directions by comparing effect sizes of horizontal and vertical measures, and by investigating the correlation of saccadic measures with underlying gray matter loss. Consistent with previous studies, AS and MG impairments were detected prior to the onset of manifest disease. Furthermore, the largest effect sizes were found for vertical saccades. A subset of participants (12 CAG-, 12 premanifest CAG+, 7 manifest HD) underwent magnetic resonance imaging, and an automated parcellation and segmentation procedure was used to extract thickness and volume measures in saccade-generating and inhibiting regions. These measures were then tested for associations with saccadic impairment. Latency of vertical AS was significantly associated with atrophy in the left superior frontal gyrus, left inferior parietal lobule, and bilateral caudate nuclei. This study suggests an important role for measuring vertical saccades. Vertical saccades may possess more statistical power than horizontal saccades, and the latency of vertical AS is associated with gray matter loss in both cortical and subcortical regions important in saccade function. |
Nicholas D. Smith; David P. Crabb; Fiona C. Glen; Robyn Burton; David F. Garway-Heath Eye movements in patients with glaucoma when viewing images of everyday scenes Journal Article In: Seeing and Perceiving, vol. 25, no. 5, pp. 471–492, 2012. @article{Smith2012a, This study tests the hypothesis that patients with bilateral glaucoma exhibit different eye movements compared to normally-sighted people when viewing computer displayed photographs of everyday scenes. Thirty glaucomatous patients and 30 age-related controls with normal vision viewed images on a computer monitor whilst eye movements were simultaneously recorded using an eye tracking system. The patients demonstrated a significant reduction in the average number of saccades compared to controls (P = 0.02; mean reduction of 7% (95% confidence interval (CI): 311%)). There was no difference in average saccade amplitude between groups but there was between-person variability in patients. The average elliptical region scanned by the patients by a bivariate contour ellipse area (BCEA) analysis, was more restricted compared to controls (P = 0.004; mean reduction of 23% (95% (CI): 1135%)). A novel analysis mapping areas of interest in the images indicated a weak association between severity of functional deficit and a tendency to not view regions typically viewed by the controls. In conclusion, some eye movements in some patients with bilateral glaucomatous defects differ from normal-sighted people of a similar age when viewing images of everyday scenes, providing evidence for a potential new window for looking into the functional consequences of the disease. |
Nicholas D. Smith; Fiona C. Glen; David P. Crabb Eye movements during visual search in patients with glaucoma Journal Article In: BMC Ophthalmology, vol. 12, pp. 1–11, 2012. @article{Smith2012, BACKGROUND: Glaucoma has been shown to lead to disability in many daily tasks including visual search. This study aims to determine whether the saccadic eye movements of people with glaucoma differ from those of people with normal vision, and to investigate the association between eye movements and impaired visual search. METHODS: Forty patients (mean age: 67 [SD: 9] years) with a range of glaucomatous visual field (VF) defects in both eyes (mean best eye mean deviation [MD]: -5.9 (SD: 5.4) dB) and 40 age-related people with normal vision (mean age: 66 [SD: 10] years) were timed as they searched for a series of target objects in computer displayed photographs of real world scenes. Eye movements were simultaneously recorded using an eye tracker. Average number of saccades per second, average saccade amplitude and average search duration across trials were recorded. These response variables were compared with measurements of VF and contrast sensitivity. RESULTS: The average rate of saccades made by the patient group was significantly smaller than the number made by controls during the visual search task (P = 0.02; mean reduction of 5.6% (95% CI: 0.1 to 10.4%). There was no difference in average saccade amplitude between the patients and the controls (P = 0.09). Average number of saccades was weakly correlated with aspects of visual function, with patients with worse contrast sensitivity (PR logCS; Spearman's rho: 0.42; P = 0.006) and more severe VF defects (best eye MD; Spearman's rho: 0.34; P = 0.037) tending to make less eye movements during the task. Average detection time in the search task was associated with the average rate of saccades in the patient group (Spearman's rho = -0.65; P < 0.001) but this was not apparent in the controls. CONCLUSIONS: The average rate of saccades made during visual search by this group of patients was fewer than those made by people with normal vision of a similar average age. There was wide variability in saccade rate in the patients but there was an association between an increase in this measure and better performance in the search task. Assessment of eye movements in individuals with glaucoma might provide insight into the functional deficits of the disease. |
Sue Lord; Neil Archibald; Urs P. Mosimann; David J. Burn; Lynn Rochester Dorsal rather than ventral visual pathways discriminate freezing status in Parkinson's disease Journal Article In: Parkinsonism and Related Disorders, vol. 18, no. 10, pp. 1094–1096, 2012. @article{Lord2012, Background: Although visuospatial deficits have been linked with freezing of gait (FOG) in Parkinson's disease (PD), the specific effects of dorsal and ventral visual pathway dysfunction on FOG is not well understood. Method: We assessed visuospatial function in FOG using an angle discrimination test (dorsal visual pathway bias) and overlapping figure test (ventral visual pathway bias), and recorded overall response time, mean fixation duration and dwell time. Covariate analysis was conducted controlling for disease duration, motor severity, contrast sensitivity and attention with Bonferroni adjustments for multiple comparisons. Results: Twenty seven people with FOG, 27 people without FOG and 24 controls were assessed. Average fixation duration during angle discrimination distinguished freezing status: [F (1, 43) = 4.77 p < 0.05] (1-way ANCOVA). Conclusion: Results indicate a preferential dysfunction of dorsal occipito-parietal pathways in FOG, independent of disease severity, attentional deficit, and contrast sensitivity. |
George T. Gitchel; Paul A. Wetzel; Mark S. Baron Pervasive ocular tremor in patients with parkinson disease Journal Article In: Archives of Neurology, vol. 69, no. 8, pp. 1011–1017, 2012. @article{Gitchel2012, OBJECTIVE: To further assess oculomotor control of patients with Parkinson disease (PD) during fixation and with movement. DESIGN: Case-control study. SETTING: A Parkinson disease research, education, and clinical center. PATIENTS One hundred twelve patients with PD, including 18 de novo untreated patients, and 60 age-matched controls. INTERVENTION: Modern, precise eye tracking technology was used to assess oculomotor parameters. Oculomotor function was compared between groups during fixation and while tracking a randomly displaced target on a PC monitor. MAIN OUTCOME MEASURES: Fixation stability and saccadic parameters. RESULTS: All patients with PD and 2 of 60 control subjects showed oscillatory fixation instability (ocular tremor), with an average fundamental frequency of 5.7 Hz and average magnitude of 0.27°. Saccadic parameters and occurrences of square wave jerks did not differ between subjects with PD and controls. The amplitude and frequency of fixation instability did not correlate with disease duration, clinical Unified Parkinson's Disease Rating Scale scores, or dopa-equivalent dosing. No differences in oculomotor parameters were found between medicated and unmedicated patients with PD. CONCLUSIONS: All patients with PD exhibited persistent ocular tremor that prevented stability during fixation. The pervasiveness and specificity of this feature suggest that modern, precise oculomotor testing could provide a valuable early physiological biomarker for diagnosing PD. |
Esther G. González; Agnes M. F. Wong; Ewa Niechwiej-Szwedo; Luminita Tarita-Nistor; Martin J. Steinbach Eye position stability in amblyopia and in normal binocular vision Journal Article In: Investigative Ophthalmology & Visual Science, vol. 53, no. 9, pp. 5386–5394, 2012. @article{Gonzalez2012, PURPOSE: We investigated whether the sensory impairments of amblyopia are associated with a decrease in eye position stability (PS). METHODS: The positions of both eyes were recorded simultaneously in three viewing conditions: binocular, monocular fellow eye viewing (right eye for controls), and monocular amblyopic eye viewing (left eye for controls). For monocular conditions, movements of the covered eye were also recorded (open-loop testing). Bivariate contour ellipses (BCEAs), representing the region over which eye positions were found 68.2% of the time, were calculated and normalized by log transformation. RESULTS: For controls, there were no differences between eyes. Binocular PS (log(10)BCEA = -0.88) was better than monocular PS (log(10)BCEA = -0.59) indicating binocular summation, and the PS of the viewing eye was better than that of the covered eye (log(10)BCEA = -0.33). For patients, the amblyopic eye exhibited a significant decrease in PS during amblyopic eye (log(10)BCEA = -0.20), fellow eye (log(10)BCEA = 0.0004), and binocular (log(10)BCEA = -0.44) viewing. The PS of the fellow eye depended on viewing condition: it was comparable to controls during binocular (log(10)BCEA = -0.77) and fellow eye viewing (log(10)BCEA = -0.52), but it decreased during amblyopic eye viewing (log(10)BCEA = 0.08). Patients exhibited binocular summation during fellow eye viewing, but not during amblyopic eye viewing. Decrease in PS in patients was mainly due to slow eye drifts. CONCLUSIONS: Deficits in spatiotemporal vision in amblyopia are associated with poor PS. PS of amblyopic and fellow eyes is differentially affected depending on viewing condition. |
Joshua A. Granek; Laure Pisella; Annabelle Blangero; Yves Rossetti; Lauren E. Sergio The role of the caudal superior parietal lobule in updating hand location in peripheral vision: Further evidence from optic ataxia Journal Article In: PLoS ONE, vol. 7, no. 10, pp. e46619, 2012. @article{Granek2012, Patients with optic ataxia (OA), who are missing the caudal portion of their superior parietal lobule (SPL), have difficulty performing visually-guided reaches towards extra-foveal targets. Such gaze and hand decoupling also occurs in commonly performed non-standard visuomotor transformations such as the use of a computer mouse. In this study, we test two unilateral OA patients in conditions of 1) a change in the physical location of the visual stimulus relative to the plane of the limb movement, 2) a cue that signals a required limb movement 180° opposite to the cued visual target location, or 3) both of these situations combined. In these non-standard visuomotor transformations, the OA deficit is not observed as the well-documented field-dependent misreach. Instead, OA patients make additional eye movements to update hand and goal location during motor execution in order to complete these slow movements. Overall, the OA patients struggled when having to guide centrifugal movements in peripheral vision, even when they were instructed from visual stimuli that could be foveated. We propose that an intact caudal SPL is crucial for any visuomotor control that involves updating ongoing hand location in space without foveating it, i.e. from peripheral vision, proprioceptive or predictive information. |
Britta Hahn; Benjamin M. Robinson; Alexander N. Harvey; Samuel T. Kaiser; Carly J. Leonard; Steven J. Luck; James M. Gold Visuospatial attention in schizophrenia: Deficits in broad monitoring Journal Article In: Journal of Abnormal Psychology, vol. 121, no. 1, pp. 119–128, 2012. @article{Hahn2012, Although selective attention is thought to be impaired in people with schizophrenia (PSZ), prior research has found no deficit in the ability to select one location and withdraw attention from another. PSZ and healthy control subjects (HCS) performed a stimulus detection task in which one, two, or all four peripheral target locations were cued. When one or two locations were cued, both PSZ and HCS responded faster when the target appeared at a cued than uncued location. However, increases in the number of validly cued locations had much more deleterious effects on performance for PSZ than HCS, especially for targets of low contrast whose detection was more dependent on attention. PSZ also responded more slowly in trials with four cued locations relative to trials with one or two invalidly cued locations. Thus, visuospatial attention deficits in schizophrenia arise when broad monitoring is required rather than when attention must be focused narrowly. |
Ben Harkin; Sébastien Miellet; Klaus Kessler What checkers actually check: An eye tracking study of inhibitory control and working memory Journal Article In: PLoS ONE, vol. 7, no. 9, pp. e44689, 2012. @article{Harkin2012, Background: Not only is compulsive checking the most common symptom in Obsessive Compulsive Disorder (OCD) with an estimated prevalence of 50–80% in patients, but approximately ~15% of the general population reveal subclinical checking tendencies that impact negatively on their performance in daily activities. Therefore, it is critical to understand how checking affects attention and memory in clinical as well as subclinical checkers. Eye fixations are commonly used as indicators for the distribution of attention but research in OCD has revealed mixed results at best. Methodology/Principal Finding: Here we report atypical eye movement patterns in subclinical checkers during an ecologically valid working memory (WM) manipulation. Our key manipulation was to present an intermediate probe during the delay period of the memory task, explicitly asking for the location of a letter, which, however, had not been part of the encoding set (i.e., misleading participants). Using eye movement measures we now provide evidence that high checkers' inhibitory impairments for misleading information results in them checking the contents of WM in an atypical manner. Checkers fixate more often and for longer when misleading information is presented than non-checkers. Specifically, checkers spend more time checking stimulus locations as well as locations that had actually been empty during encoding. Conclusions/Significance: We conclude that these atypical eye movement patterns directly reflect internal checking of memory contents and we discuss the implications of our findings for the interpretation of behavioural and neuropsychological data. In addition our results highlight the importance of ecologically valid methodology for revealing the impact of detrimental attention and memory checking on eye movement patterns. |
Christoph Helmchen; Jonas Pohlmann; Peter Trillenberg; Rebekka Lencer; Julia Graf; Andreas Sprenger Role of anticipation and prediction in smooth pursuit eye movement control in Parkinson's disease Journal Article In: Movement Disorders, vol. 27, no. 8, pp. 1012–1018, 2012. @article{Helmchen2012, Patients with Parkinson's disease (PD) have difficulties in the control of self-guided (i.e., internally driven) movements. The basal ganglia provide a nonspecific internal cue for the development of a preparatory activity for a given movement in the sequence of repetitive movements. Controversy surrounds the question of whether PD patients are capable of (1) anticipating (before an external trigger appears; i.e., anticipation) and (2) predicting movement velocity once a moving target shortly disappears from the visual scene (i.e., prediction). To dissociate between these two components, we examined internally driven (extraretinal generated) smooth pursuit eye movements in PD patients and age-matched healthy controls by systematically varying target blanking periods of a trapezoidally moving target in four paradigms (initial blanking, midramp blanking, blanking after a short ramp, and no blanking). Compared to controls, PD patients showed (1) decreased smooth pursuit gain (without blanking), (2) deficient anticipatory pursuit (prolonged pursuit initiation latency; reduced eye velocity before target onset in the early onset blanking paradigm), and (3) preserved extraretinal predictive pursuit velocity (midramp target blanking). Deficient anticipation of future target motion was not related to either disease duration or the general motor impairment (UPDRS). We conclude that PD patients have difficulties in anticipating future target motion, which may play a role for the mechanisms involved in deficient gait initiation and termination of PD. In contrast, they remain unimpaired in their capacity of building up an internal representation of continuous target motion. This may explain the clinical advantage of medical devices that use visual motion to improve gait initiation (e.g., "PD glasses"). |
Constanze Hesse; Keira Ball; Thomas Schenk Visuomotor performance based on peripheral vision is impaired in the visual form agnostic patient DF Journal Article In: Neuropsychologia, vol. 50, no. 1, pp. 90–97, 2012. @article{Hesse2012, The perception-action model states that visual information is processed in different cortical areas depending on the purpose for which the information is acquired. Specifically, it was suggested that the ventral stream mediates visual perception, whereas the dorsal stream primarily processes visual information for the guidance of actions (Goodale & Milner, 1992). Evidence for the model comes from patient studies showing that patients with ventral stream damage (visual form agnosia) and patients with dorsal stream damage (optic ataxia) show divergent performance in action and perception tasks. Whereas DF, a patient suffering from visual form agnosia, was found to perform well in visuomotor tasks despite her inability to use vision for perceptual tasks, patients with optic ataxia show usually the opposite pattern, i.e. good perception but impaired visuomotor control. The finding that both disorders seem to provoke a mirror-reversed pattern of spared and impaired visual functions, led to the belief that optic ataxia and visual form agnosia can be considered as complementary disorders. However, the visuomotor performance of patients with optic ataxia is typically only impaired when they are tested in visual periphery while being often preserved when tested in central vision. Here, we show that DF's visuomotor performance is also only preserved when the target is presented centrally. Her reaching and grasping movements to targets in peripheral vision are abnormal. Our findings indicate that DF's visuomotor performance is quite similar to the visuomotor performance of patients with optic ataxia which undermines previous suggestions that the two disorders form a double-dissociation. |
Elmar H. Pinkhardt; Reinhart Jurgens; Dorothée Lulé; Johanna Heimrath; Albert C. Ludolph; Wolfgang Becker; Jan Kassubek Eye movement impairments in Parkinson's disease: Possible role of extradopaminergic mechanisms Journal Article In: BMC Neurology, vol. 12, no. 5, pp. 1–8, 2012. @article{Pinkhardt2012, Background: The basal ganglia (BG) are thought to play an important role in the control of eye movements. Accordingly, the broad variety of subtle oculomotor alterations that has been described in Parkinson's disease (PD) are generally attributed to the dysfunction of the BG dopaminergic system. However, the present study suggest that dopamine substitution is much less effective in improving oculomotor performance than it is in restoring skeletomotor abilities.Methods: We investigated reactive, visually guided saccades (RS), smooth pursuit eye movements (SPEM), and rapidly left-right alternating voluntary gaze shifts (AVGS) by video-oculography in 34 PD patients receiving oral dopaminergic medication (PD-DA), 14 patients with deep brain stimulation of the nucleus subthalamicus (DBS-STN), and 23 control subjects (CTL);In addition, we performed a thorough review of recent literature according therapeuthic effects on oculomotor performance in PD by switching deep brain stimulation off and on in the PD-DBS patients, we achieved swift changes between their therapeutic states without the delays of dopamine withdrawal. In addition, participants underwent neuropsychological testing.Results: Patients exhibited the well known deficits such as increased saccade latency, reduced SPEM gain, and reduced frequency and amplitude of AVGS. Across patients none of the investigated oculomotor parameters correlated with UPDRS III whereas there was a negative correlation between SPEM gain and susceptibility to interference (Stroop score). Of the observed deficiencies, DBS-STN slightly improved AVGS frequency but neither AVGS amplitude nor SPEM or RS performance.Conclusions: We conclude that the impairment of SPEM in PD results from a cortical, conceivably non-dopaminergic dysfunction, whereas patients' difficulty to rapidly execute AVGS might be related to their BG dysfunction. |
Ebrahim Pishyareh; Mehdi Tehrani-Doost; Javad Mahmoudi-Gharaei; Anahita Khorrami; Mitra Joudi; Mehrnoosh Ahmadi Attentional bias towards emotional scenes in boys with attention deficit hyperactivity disorder Journal Article In: Iranian Journal of Psychiatry, vol. 7, no. 2, pp. 93–96, 2012. @article{Pishyareh2012, OBJECTIVE: Children with attention-deficit/hyperactivity disorder (ADHD) react explosively and inappropriately to emotional stimuli. It could be hypothesized that these children have some impairment in attending to emotional cues. Based on this hypothesis, we conducted this study to evaluate visual directions of children with ADHD towards paired emotional scenes. METHOD: Thirty boys between the ages of 6 and 11 years diagnosed with ADHD were compared with 30 age-matched normal boys. All participants were presented paired emotional and neutral scenes in the four following categories: pleasant-neutral; pleasant-unpleasant; unpleasant-neutral; and neutral - neutral. Meanwhile, their visual orientations towards these pictures were evaluated using the eye tracking system. The number and duration of first fixation and duration of first gaze were compared between the two groups using the MANOVA analysis. The performance of each group in different categories was also analyzed using the Friedman test. RESULTS: With regards to duration of first gaze, which is the time taken to fixate on a picture before moving to another picture, ADHD children spent less time on pleasant pictures compared to normal group, while they were looking at pleasant - neutral and unpleasant - pleasant pairs. The duration of first gaze on unpleasant pictures was higher while children with ADHD were looking at unpleasant - neutral pairs (P<0.01). CONCLUSION: Based on the findings of this study it could be concluded that children with ADHD attend to unpleasant conditions more than normal children which leads to their emotional reactivity. |
Ned Jenkinson; John Stuart Brittain; Stephen L. Hicks; Christopher Kennard; Tipu Z. Aziz On the origin of oscillopsia during pedunculopontine stimulation Journal Article In: Stereotactic and Functional Neurosurgery, vol. 90, no. 2, pp. 124–129, 2012. @article{Jenkinson2012, We report a case of induced oscillopsia caused by deep brain stimulation (DBS) of the pedunculopontine nucleus (PPN). Recent reports have described involuntary oscillopsia during DBS of the PPN that patients have described as trembling vision. Here we substantiate this observation using infra-red eye tracking. It has been suggested that this phenomenon might be used as an indicator of accurate targeting of the PPN with DBS. Our observations suggest that this phenomenon may not be related to a constricted anatomical structure and therefore such practise may be unwise. Scrutiny has led us to believe that the oscillopsia in our patient is not caused by direct stimulation of the oculomotor nerve as suggested in a previous report, but by stimulation of fibres in the uncinate fasciculus of the cerebellum and the superior cerebellar peduncle, which in turn stimulate the saccadic pre-motor neurones in the brainstem. |
Solène Kalénine; Daniel Mirman; Laurel J. Buxbaum A combination of thematic and similarity-based semantic processes confers resistance to deficit following left hemisphere stroke Journal Article In: Frontiers in Human Neuroscience, vol. 6, pp. 106, 2012. @article{Kalenine2012, Semantic knowledge may be organized in terms of similarity relations based on shared features and/or complementary relations based on co-occurrence in events. Thus, relationships between manipulable objects such as tools may be defined by their functional properties (what the objects are used for) or thematic properties (e.g., what the objects are used with or on). A recent study from our laboratory used eye-tracking to examine incidental activation of semantic relations in a word-picture matching task and found relatively early activation of thematic relations (e.g., broom-dustpan), later activation of general functional relations (e.g., broom-sponge), and an intermediate pattern for specific functional relations (e.g., broom-vacuum cleaner). Combined with other recent studies, these results suggest that there are distinct semantic systems for thematic and similarity-based knowledge and that the "specific function" condition drew on both systems. This predicts that left hemisphere stroke that damages either system (but not both) may spare specific function processing. The present experiment tested these hypotheses using the same experimental paradigm with participants with left hemisphere lesions (N = 17). The results revealed that, compared to neurologically intact controls (N = 12), stroke participants showed later activation of thematic and general function relations, but activation of specific function relations was spared and was significantly earlier for stroke participants than controls. Across the stroke participants, activation of thematic and general function relations was negatively correlated, further suggesting that damage tended to affect either one semantic system or the other. These results support the distinction between similarity-based and complementarity-based semantic relations and suggest that relations that draw on both systems are relatively more robust to damage. |
Makoto Kobayashi; Atsuhiko Sugiyama In: Internal Medicine, vol. 51, no. 15, pp. 2025–2029, 2012. @article{Kobayashi2012, A 72-year-old man presented with dizziness and left hand muscle atrophy. Magnetic resonance imaging revealed a spinal cord cavity and descent of the cerebellar tonsils. His diagnosis was Chiari I malformation with syringomyelia. No cerebellar signs were observed on physical examination. The cause of dizziness was investigated using a video-based eye movement tracker, which revealed a downward smooth pursuit velocity gain significantly below normal when expressed relative to the horizontal pursuit velocity gain. Vestibulocerebellar damage can cause mild downward pursuit deficit. The downward to horizontal smooth pursuit velocity gain ratio may be a more sensitive means of detecting vestibulocerebellar damage early. |
2011 |
L. Elliot Hong; Gunvant K. Thaker; Robert P. McMahon; Ann Summerfelt; Jill RachBeisel; Rebecca L. Fuller; Ikwunga Wonodi; Robert W. Buchanan; Carol Myers; Stephen J. Heishman; Jeff Yang; Adrienne Nye In: Archives of General Psychiatry, vol. 68, no. 12, pp. 1195–1206, 2011. @article{Hong2011, CONTEXT: The administration of nicotine transiently improves many neurobiological and cognitive functions in schizophrenia and schizoaffective disorder. It is not yet clear which nicotinic acetylcholine receptor (nAChR) subtype or subtypes are responsible for these seemingly pervasive nicotinic effects in schizophrenia and schizoaffective disorder. OBJECTIVE: Because α4β2 is a key nAChR subtype for nicotinic actions, we investigated the effect of varenicline tartrate, a relatively specific α4β2 partial agonist and antagonist, on key biomarkers that are associated with schizophrenia and are previously shown to be responsive to nicotinic challenge in humans. DESIGN: A double-blind, parallel, randomized, placebo-controlled trial of patients with schizophrenia or schizoaffective disorder to examine the effects of varenicline on biomarkers at 2 weeks (short-term treatment) and 8 weeks (long-term treatment), using a slow titration and moderate dosing strategy for retaining α4β2-specific effects while minimizing adverse effects. SETTING: Outpatient clinics. PARTICIPANTS: A total of 69 smoking and nonsmoking patients; 64 patients completed week 2, and 59 patients completed week 8. Intervention Varenicline. MAIN OUTCOME MEASURES: Prepulse inhibition, sensory gating, antisaccade, spatial working memory, eye tracking, processing speed, and sustained attention. RESULTS: A moderate dose of varenicline (1) significantly reduced the P50 sensory gating deficit in nonsmokers after long-term treatment (P = .006), (2) reduced startle reactivity (P = .02) regardless of baseline smoking status, and (3) improved executive function by reducing the antisaccadic error rate (P = .03) regardless of smoking status. A moderate dose of varenicline had no significant effect on spatial working memory, predictive and maintenance pursuit measures, processing speed, or sustained attention by Conners' Continuous Performance Test. Clinically, there was no evidence of exacerbation of psychiatric symptoms, psychosis, depression, or suicidality using a gradual titration (1-mg daily dose). CONCLUSIONS: Moderate-dose treatment with varenicline has a unique treatment profile on core schizophrenia-related biomarkers. Further development is warranted for specific nAChR compounds and dosing and duration strategies to target subgroups of schizophrenic patients with specific biological deficits. |
V. C. Huddy; Timothy L. Hodgson; M. A. Ron; Thomas R. E. Barnes; Eileen M. Joyce Abnormal negative feedback processing in first episode schizophrenia: Evidence from an oculomotor rule switching task Journal Article In: Psychological Medicine, vol. 41, no. 9, pp. 1805–1814, 2011. @article{Huddy2011, Background. Previous studies have shown that patients with schizophrenia are impaired on executive tasks, where positive and negative feedbacks are used to update task rules or switch attention. However, research to date using saccadic tasks has not revealed clear deficits in task switching in these patients. The present study used an oculomotor ‘ rule switching ' task to investigate the use of negative feedback when switching between task rules in people with schizophrenia. Method. A total of 50 patients with first episode schizophrenia and 25 healthy controls performed a task in which the association between a centrally presented visual cue and the direction of a saccade could change from trial to trial. Rule changes were heralded by an unexpected negative feedback, indicating that the cue-response mapping had reversed. Results. Schizophrenia patients were found to make increased errors following a rule switch, but these were almost entirely the result of executing saccades away from the location at which the negative feedback had been presented on the preceding trial. This impairment in negative feedback processing was independent of IQ. Conclusions. The results not only confirm the existence of a basic deficit in stimulus–response rule switching in schizophrenia, but also suggest that this arises from aberrant processing of response outcomes, resulting in a failure to appropriately update rules. The findings are discussed in the context of neurological and pharmacological abnormalities in the conditions that may disrupt prediction error signalling in schizophrenia. |
Daniel P. Kennedy; Ralph Adolphs Impaired fixation to eyes following amygdala damage arises from abnormal bottom-up attention Journal Article In: Neuropsychologia, vol. 49, no. 4, pp. 589–595, 2011. @article{Kennedy2011, SM is a patient with complete bilateral amygdala lesions who fails to fixate the eyes in faces and is consequently impaired in recognizing fear (Adolphs et al., 2005). Here we first replicated earlier findings in SM of reduced gaze to the eyes when seen in whole faces. Examination of the time course of fixations revealed that SM's reduced eye contact is particular pronounced in the first fixation to the face, and less abnormal in subsequent fixations. In a second set of experiments, we used a gaze-contingent presentation of faces with real time eye tracking, wherein only a small region of the face is made visible at the center of gaze. In essence, viewers explore the face by moving a small searchlight over the face with their gaze. Under such viewing conditions, SM's fixations to eye region of faces became entirely normalized. We suggest that this effect arises from the absence of bottom-up effects due to the facial features, allowing gaze location to be driven entirely by top-down control. Together with SM's failure to fixate the eyes in whole faces primarily at the very first saccade, the findings suggest that the saliency of the eyes normally attract our gaze in an amygdala-dependent manner. Impaired eye gaze is also a prominent feature of several psychiatric illnesses in which the amygdala has been hypothesized to be dysfunctional, and our findings and experimental manipulation may hold promise for interventions in such populations, including autism and fragile X syndrome. |
Lisa Kloft; Eva Kischkel; Norbert Kathmann; Benedikt Reuter Evidence for a deficit in volitional action generation in patients with obsessive-compulsive disorder Journal Article In: Psychophysiology, vol. 48, no. 6, pp. 755–761, 2011. @article{Kloft2011, Obsessive-compulsive disorder (OCD) patients show deficits in tasks of executive functioning like the antisaccade (AS) task. These deficits suggest problems in response inhibition or volitional saccade generation. Thirty patients (15 nonmedicated) and 30 healthy subjects performed antisaccades and simple volitional saccades (SVS), that is, centrally cued saccades. In SVS, two aspects of volitional saccade generation were disentangled: response selection and initiation. Latencies of OCD patients were increased in volitional saccades independent of response selection demands. AS performance did not differ. Across groups, latencies in AS were faster than in SVS. Medicated patients did not differ from nonmedicated patients. In sum, response initiation is deficient in OCD patients, which may reflect a general problem in volitional action generation. This deficit did not affect antisaccade performance, possibly due to a lower volitional demand in that task. |
Christopher R. Sears; Kristin R. Newman; Jennifer D. Ference; Charmaine L. Thomas Attention to emotional images in previously depressed individuals: An eye-tracking study Journal Article In: Cognitive Therapy and Research, vol. 35, no. 6, pp. 517–528, 2011. @article{Sears2011, Depression and dysphoria are associated with attention and memory biases for emotional information (Williams et al. 1997; Yiend in Cogn Emot 24:3-47, 2010), which are postulated to reflect stable vulnerability factors for the development and recurrence of depression (Gotlib and Joormann in Annu Rev Clin Psychol 6:285-312, 2010). The present study looked for evidence of attention and memory biases in individuals with a self-reported history of depression, compared to individuals with dysphoria and individuals with no history of depression. Participants viewed sets of depression-related, anxiety-related, positive, and neutral images while their eye fixations were tracked and recorded. Incidental recognition of the images was assessed 7 days later. Consistent with previous studies (Kellough et al. in Behav Res Therapy 46:1238-1243, 2008; Sears et al. in Cogn Emot 24:1349-1368, 2010), dysphoric individuals spent significantly less time attending to positive images than never depressed individuals, and it was also found that previously depressed individuals exhibited the same attentional bias. Previously depressed individuals also attended to anxiety-related images more than never depressed individuals. A bias in the initial orienting of attention was observed, with previously depressed and dysphoric individuals orienting to depression-images more frequently than never depressed participants. The recognition memory data showed that previously depressed and dysphoric individuals had poorer memory than never depressed individuals, but there was no evidence of a memory bias for either group. Implications for cognitive models of depression and depression vulnerability are discussed. |
Sara Ann Simpson; Mathias Abegg; Jason J. S. Barton Rapid adaptation of visual search in simulated hemianopia Journal Article In: Cerebral Cortex, vol. 21, no. 7, pp. 1593–1601, 2011. @article{Simpson2011, Patients with homonymous hemianopia have altered visual search patterns, but it is unclear how rapidly this develops and whether it reflects a strategic adaptation to altered perception or plastic changes to tissue damage. To study the temporal dynamics of adaptation alone, we used a gaze-contingent display to simulate left or right hemianopia in 10 healthy individuals as they performed 25 visual search trials. Visual search was slower and less accurate in hemianopic than in full-field viewing. With full-field viewing, there were improvements in search speed, fixation density, and number of fixations over the first 9 trials, then stable performance. With hemianopic viewing, there was a rapid shift of fixation into the blind field over the first 5-7 trials, followed by continuing gradual improvements in completion time, number of fixations, and fixation density over all 25 trials. We conclude that in the first minutes after onset of hemianopia, there is a biphasic pattern of adaptation to altered perception: an early rapid qualitative change that shifts visual search into the blind side, followed by more gradual gains in the efficiency of using this new strategy, a pattern that has parallels in other studies of motor learning. |
Nicholas D. Smith; David P. Crabb; David F. Garway-Heath An exploratory study of visual search performance in glaucoma Journal Article In: Ophthalmic and Physiological Optics, vol. 31, no. 3, pp. 225–232, 2011. @article{Smith2011, PURPOSE: Visual search plays an integral role in many daily activities. This study aimed to determine whether patients with glaucoma are slower than visually healthy age-matched individuals when searching for items in computer displayed images. METHODS: Forty participants were recruited for the study: 20 patients with a clinical diagnosis of glaucoma and 20 age-similar visually healthy control subjects. All participants had visual acuity of 6/12 or better. Participants were presented with 20 images with Landolt C symbols and 15 photographic images of everyday scenes on a computer. The time taken by each participant to locate a specified item in each image was recorded. Average search times were calculated across participants and compared between groups. RESULTS: All the patients had visual field defects in both eyes. On average, the patients also differed from control subjects by binocular contrast sensitivity measurements (p = 0.01) and visual acuity (p = 0.003). The patients (mean age = 67 years, S.D.: 10 years) and controls (mean age: 67 years, S.D.: 11 years) were age similar (p = 0.40). The median search time for patients finding target items in photographs of everyday scenes was 15.2 s (interquartile range 9.4-20.6 s) and this was significantly slower than the median time (10.0 s; interquartile range 7.2-10.3 s) taken by the controls (p = 0.007). There was no statistical evidence for a difference in median search times between groups in the Landolt C search task (p = 0.24). CONCLUSION: Some individuals with glaucomatous visual field defects in both eyes find it especially difficult to locate objects in photographs of everyday scenes when compared to visually healthy individuals of a similar age. |
Zhong I. Wang; Louis F. Dell'Osso A unifying model-based hypothesis for the diverse waveforms of infantile nystagmus syndrome Journal Article In: Journal of Eye Movement Research, vol. 4, no. 1, pp. 1–18, 2011. @article{Wang2011, We expanded the original behavioral Ocular Motor System (OMS) model for Infantile Nystagmus Syndrome (INS) by incorporating common types of jerk waveforms within a unifying mechanism. Alexander's law relationships were used to produce desired INS null positions and sharpness. At various gaze angles, these relationships influenced the IN slow-phase amplitudes differently, thereby mimicking the gaze-angle effects of INS patients. Transitions from pseudopendular with foveating saccades to jerk waveforms required replacing braking saccades with foveating fast phases and adding a resettable neural integrator in the pursuit pre-motor circuitry. The robust simulations of accurate OMS behavior in the presence of diverse INS waveforms demonstrate that they can all be generated by a loss of pursuit-system damping, supporting this hypothetical origin. |
C. Yu-Wai-Man; K. Petheram; A. W. Davidson; T. Williams; P. G. Griffiths A supranuclear disorder of ocular motility as a rare initial presentation of motor neurone disease Journal Article In: Neuro-Ophthalmology, vol. 35, no. 1, pp. 38–39, 2011. @article{YuWaiMan2011, A case is described of motor neurone disease presenting with an ocular motor disorder characterised by saccadic intrusions, impaired horizontal and vertical saccades, and apraxia of eyelid opening. The occurrence of eye movement abnormalities in motor neurone disease is discussed. |
Zheng Tai; Richard W. Hertle; Richard A. Bilonick; Dongsheng Yang A new algorithm for automated nystagmus acuity function analysis Journal Article In: British Journal of Ophthalmology, vol. 95, no. 6, pp. 832–836, 2011. @article{Tai2011, Aims: We developed a new data analysis algorithm called the automated nystagmus acuity function (ANAF) to automatically assess nystagmus acuity function. We compared results from the ANAF with those of the well-known expanded nystagmus acuity function (NAFX). Methods: Using the ANAF and NAFX, we analysed 60 segments of nystagmus data collected with a video-based eye tracking system (EyeLink 1000) from 30 patients with infantile or mal-development fusional nystagmus. The ANAF algorithm used the best-foveation positions (not true foveation positions) and all data points in each nystagmus cycle to calculate a nystagmus acuity function. Results: The ANAF automatically produced a nystagmus acuity function in a few seconds because manual identification of foveation eye positions is not required. A structural equation model was used to compare the ANAF and NAFX. Both ANAF and NAFX have similar measurement imprecision and relatively little bias. The estimated bias was not statistically significant for either methods or replicates. Conclusions: We conclude that the ANAF is a valid and efficient algorithm for determining a nystagmus acuity function. |
Luminita Tarita-Nistor; Michael H. Brent; Martin J. Steinbach; Esther G. González Fixation stability during binocular viewing in patients with age-related macular degeneration Journal Article In: Investigative Ophthalmology & Visual Science, vol. 52, no. 3, pp. 1887–1893, 2011. @article{TaritaNistor2011, PURPOSE: The authors examined the fixation stability of patients with age-related macular degeneration (AMD) and large interocular acuity differences, testing them in monocular and binocular viewing conditions. The relationship between fixation stability and visual performance during monocular and binocular viewing was also studied. METHODS: Twenty patients with AMD participated. Their monocular and binocular distance acuities were measured with the ETDRS charts. Fixation stability of the better and worse eye were recorded monocularly with the MP-1 microperimeter (Nidek Technologies Srl., Vigonza, PD, Italy) and binocularly with an EyeLink eye tracker (SR Research Ltd., Mississauga, Ontario, Canada). Additional recordings of monocular fixations were obtained with the EyeLink in viewing conditions when one eye viewed the target while the fellow eye was covered by an infrared filter so it could not see the target. RESULTS: Fixation stability of the better eye did not change across viewing conditions. Fixation stability of the worse eye was 84% to 100% better in the binocular condition than in monocular conditions. Fixation stability of the worse eye was significantly larger (P < 0.05) than that of the better eye when recorded monocularly with the MP-1 microperimeter. This difference was dramatically reduced in the binocular condition but remained marginally significant (95% confidence interval, -0.351 to -0.006). For the better eye, there was a moderate relationship between fixation stability and visual acuity, both monocular and binocular, in all conditions in which this eye viewed the target. CONCLUSIONS: Fixational ocular motor control and visual acuity are driven by the better-seeing eye when patients with AMD and large interocular acuity differences perform the tasks binocularly. |
Katharine N. Thakkar; Jeffrey D. Schall; Leanne Boucher; Gordon D. Logan; Sohee Park Response inhibition and response monitoring in a saccadic countermanding task in schizophrenia Journal Article In: Biological Psychiatry, vol. 69, no. 1, pp. 55–62, 2011. @article{Thakkar2011, Background: Cognitive control deficits are pervasive in individuals with schizophrenia (SZ) and are reliable predictors of functional outcome, but the specificity of these deficits and their underlying neural mechanisms have not been fully elucidated. The objective of the present study was to determine the nature of response inhibition and response monitoring deficits in SZ and their relationship to symptoms and social and occupational functioning with a behavioral paradigm that provides a translational approach to investigating cognitive control. Methods: Seventeen patients with SZ and 16 demographically matched healthy control subjects participated in a saccadic countermanding task. Performance on this task is approximated as a race between movement generation and inhibition processes; this race model provides an estimate of the time needed to cancel a planned movement. Response monitoring can be assessed by reaction time adjustments on the basis of trial history. Results: Saccadic reaction time was normal, but patients required more time to inhibit a planned saccade. The latency of the inhibitory process was associated with the severity of negative symptoms and poorer occupational functioning. Both groups slowed down significantly after correctly cancelled and erroneously noncancelled stop signal trials, but patients slowed down more than control subjects after correctly inhibited saccades. Conclusions: These results suggest that SZ is associated with a difficulty in inhibiting planned movements and an inflated response adjustment effect after inhibiting a saccade. Furthermore, behavioral results are consistent with potential abnormalities in frontal and supplementary eye fields in patients with SZ. |
Mervyn G. Thomas; Moira Crosier; Susan Lindsay; Anil Kumar; Shery Thomas; Masasuke Araki; Chris J. Talbot; Rebecca J. McLean; Mylvaganam Surendran; Katie Taylor; Bart P. Leroy; Anthony T. Moore; David G. Hunter; Richard W. Hertle; Patrick Tarpey; Andrea Langmann; Susanne Lindner; Martina Brandner; Irene Gottlob The clinical and molecular genetic features of idiopathic infantile periodic alternating nystagmus Journal Article In: Brain, vol. 134, no. 3, pp. 892–902, 2011. @article{Thomas2011, Periodic alternating nystagmus consists of involuntary oscillations of the eyes with cyclical changes of nystagmus direction. It can occur during infancy (e.g. idiopathic infantile periodic alternating nystagmus) or later in life. Acquired forms are often associated with cerebellar dysfunction arising due to instability of the optokinetic-vestibular systems. Idiopathic infantile periodic alternating nystagmus can be familial or occur in isolation; however, very little is known about the clinical characteristics, genetic aetiology and neural substrates involved. Five loci (NYS1-5) have been identified for idiopathic infantile nystagmus; three are autosomal (NYS2, NYS3 and NYS4) and two are X-chromosomal (NYS1 and NYS5). We previously identified the FRMD7 gene on chromosome Xq26 (NYS1 locus); mutations of FRMD7 are causative of idiopathic infantile nystagmus influencing neuronal outgrowth and development. It is unclear whether the periodic alternating nystagmus phenotype is linked to NYS1, NYS5 (Xp11.4-p11.3) or a separate locus. From a cohort of 31 X-linked families and 14 singletons (70 patients) with idiopathic infantile nystagmus we identified 10 families and one singleton (21 patients) with periodic alternating nystagmus of which we describe clinical phenotype, genetic aetiology and neural substrates involved. Periodic alternating nystagmus was not detected clinically but only on eye movement recordings. The cycle duration varied from 90 to 280 s. Optokinetic reflex was not detectable horizontally. Mutations of the FRMD7 gene were found in all 10 families and the singleton (including three novel mutations). Periodic alternating nystagmus was predominantly associated with missense mutations within the FERM domain. There was significant sibship clustering of the phenotype although in some families not all affected members had periodic alternating nystagmus. In situ hybridization studies during mid-late human embryonic stages in normal tissue showed restricted FRMD7 expression in neuronal tissue with strong hybridization signals within the afferent arms of the vestibulo-ocular reflex consisting of the otic vesicle, cranial nerve VIII and vestibular ganglia. Similarly within the afferent arm of the optokinetic reflex we showed expression in the developing neural retina and ventricular zone of the optic stalk. Strong FRMD7 expression was seen in rhombomeres 1 to 4, which give rise to the cerebellum and the common integrator site for both these reflexes (vestibular nuclei). Based on the expression and phenotypic data, we hypothesize that periodic alternating nystagmus arises from instability of the optokinetic-vestibular systems. This study shows for the first time that mutations in FRMD7 can cause idiopathic infantile periodic alternating nystagmus and may affect neuronal circuits that have been implicated in acquired forms. |
Mervyn G. Thomas; Irene Gottlob; Rebecca J. McLean; Gail Maconachie; Anil Kumar; Frank A. Proudlock Reading strategies in infantile nystagmus syndrome Journal Article In: Investigative Ophthalmology & Visual Science, vol. 52, no. 11, pp. 8156–8165, 2011. @article{Thomas2011a, PURPOSE: The adaptive strategies adopted by individuals with infantile nystagmus syndrome (INS) during reading are not clearly understood. Eye movement recordings were used to identify ocular motor strategies used by patients with INS during reading. METHODS: Eye movements were recorded at 500 Hz in 25 volunteers with INS and 7 controls when reading paragraphs of text centered at horizontal gaze angles of -20°, -10°, 0°, 10°, and 20°. At each location, reading speeds were measured, along with logMAR visual acuity and nystagmus during gaze-holding. Adaptive strategies were identified from slow and quick-phase patterns in the nystagmus waveform. RESULTS: Median reading speeds were 204.3 words per minute in individuals with INS and 273.6 words per minute in controls. Adaptive strategies included (1) suppression of corrective quick phases allowing involuntary slow phases to achieve the desired goal, (2) voluntarily changing the character of the involuntary slow phases using quick phases, and (3) correction of involuntary slow phases using quick phases. Several individuals with INS read more rapidly than healthy control volunteers. CONCLUSIONS: These findings demonstrate that volunteers with INS learn to manipulate their nystagmus using a range of strategies to acquire visual information from the text. These strategies include taking advantage of the stereotypical and periodic nature of involuntary eye movements to allow the involuntary eye movements to achieve the desired goal. The versatility of these adaptations yields reading speeds in those with nystagmus that are often much better than might be expected, given the degree of foveal and ocular motor deficits. |
Gurmit Uppal; Mary P. Feely; Michael D. Crossland; Luke Membrey; John Lee; Lyndon Cruz; Gary S. Rubin Assessment of reading behavior with an infrared eye tracker after 360° macular translocation for age-related macular degeneration Journal Article In: Investigative Ophthalmology & Visual Science, vol. 52, no. 9, pp. 6486–6496, 2011. @article{Uppal2011, Purpose. Macular translocation (MT360) is complex surgery used to restore reading in exudative age-related macular degeneration (AMD). MT360 involves retinal rotation and subsequent oculomotor globe counterrotation and is not without significant surgical risk. This study attempts to gauge the optimal potential of MT360 in restoring reading ability and describe the quality and extent of recovery. Methods. The six best outcomes were examined from a consecutive series of 23 MT360 cases. Reading behavior and fixation characteristics were examined with an infrared eye tracker. Results were compared to age-matched normal subjects and patients with untreated exudative and nonexudative AMD. Retinal sensitivity was examined with microperimetry to establish threshold visual function. Results. MT360 produced significant improvements in visual function over untreated disease and approximated normal function for reading speed and fixation quality. Relative to the comparative groups, eye tracking revealed the MT360 cohort generated a greater number of horizontal and vertical saccades, of longer latency and reduced velocity. In contrast, saccadic behavior when reading (forward and regressive saccades) closely matched normal function. Microperimetry revealed a reduction in the central scotoma with three patients recovering normal foveal sensitivity. Conclusions. Near normal reading function is recovered despite profound surgical disruption to the anatomy (retinal/oculomotor). MT360 restores foveal function sufficient to produce a single stable locus of fixation, with marked reduction of the central scotoma. Despite the limitations on saccadic function, the quality of reading saccadic behavior is maintained with good reading ability. Oculomotor surgery appears not to limit reading ability, and the results of retinal surgery approximate normal macular function. |
Goedele Van Belle; Thomas Busigny; Philippe Lefèvre; Sven Joubert; Olivier Felician; Francesco Gentile; Bruno Rossion; Philippe Lefèvre; Sven Joubert; Olivier Felician; Francesco Gentile; Bruno Rossion Impairment of holistic face perception following right occipito-temporal damage in prosopagnosia: Converging evidence from gaze-contingency Journal Article In: Neuropsychologia, vol. 49, no. 11, pp. 3145–3150, 2011. @article{VanBelle2011, Gaze-contingency is a method traditionally used to investigate the perceptual span in reading by selectively revealing/masking a portion of the visual field in real time. Introducing this approach in face perception research showed that the performance pattern of a brain-damaged patient with acquired prosopagnosia (PS) in a face matching task was reversed, as compared to normal observers: the patient showed almost no further decrease of performance when only one facial part (eye, mouth, nose, etc.) was available at a time (foveal window condition, forcing part-based analysis), but a very large impairment when the fixated part was selectively masked (mask condition, promoting holistic perception) (Van Belle, De Graef, Verfaillie, Busigny, & Rossion, 2010a; Van Belle, De Graef, Verfaillie, Rossion, & Lefèvre, 2010b). Here we tested the same manipulation in a recently reported case of pure prosopagnosia (GG) with unilateral right hemisphere damage (Busigny, Joubert, Felician, Ceccaldi, & Rossion, 2010). Contrary to normal observers, GG was also significantly more impaired with a mask than with a window, demonstrating impairment with holistic face perception. Together with our previous study, these observations support a generalized account of acquired prosopagnosia as a critical impairment of holistic (individual) face perception, implying that this function is a key element of normal human face recognition. Furthermore, the similar behavioral pattern of the two patients despite different lesion localizations supports a distributed network view of the neural face processing structures, suggesting that the key function of human face processing, namely holistic perception of individual faces, requires the activity of several brain areas of the right hemisphere and their mutual connectivity. |
Tobias Pflugshaupt; Julia Suchan; Marc André Mandler; Alexander N. Sokolov; Susanne Trauzettel-Klosinski; Hans-Otto Karnath Do patients with pure alexia suffer from a specific word form processing deficit? Evidence from 'wrods with trasnpsoed letetrs' Journal Article In: Neuropsychologia, vol. 49, no. 5, pp. 1294–1301, 2011. @article{Pflugshaupt2011, It is widely accepted that letter-by-letter reading and a pronounced increase in reading time as a function of word length are the hallmark features of pure alexia. Why patients show these two phenomena with respect to underlying cognitive mechanisms is, however, much less clear. Two main hypotheses have been proposed, i.e. impaired discrimination of letters and deficient processing of word forms. While the former deficit can easily be investigated in isolation, previous findings favouring the latter seem confounded. Applying a word reading paradigm with systematically manipulated letter orders in two patients with pure alexia, we demonstrate a word form processing deficit that is not attributable to sublexical letter discrimination difficulties. Moreover, pure alexia-like fixation patterns could be induced in healthy adults by having them read sentences including words with transposed letters, so-called 'jumbled words'. This further corroborates a key role of deficient word form processing in pure alexia. With regard to basic reading research, the present study extends recent evidence for relative, rather than precise, encoding of letter position in the brain.. |
Elmar H. Pinkhardt; Jan Kassubek Ocular motor abnormalities in Parkinsonian syndromes Journal Article In: Parkinsonism and Related Disorders, vol. 17, no. 4, pp. 223–230, 2011. @article{Pinkhardt2011, Oculomotor abnormalities can be observed in all Parkinsonian syndromes (PS). Nevertheless, due to the considerable overlap of oculomotor pathology in Parkinsonism, oculomotor changes are not generally considered to contribute substantially to the differential diagnosis of PS. Here we review the characteristics of oculomotor disturbances in the major PS, we provide a survey of the current concepts of the underlying neural physiology of oculomotor control and a summary of the major recording techniques for eye movements. The main focus of this review is to outline the subtle differences between apparently similar oculomotor alterations in Parkinson's disease (PD) and atypical neurodegenerative PS that can contribute to the early differential diagnosis of these entities. |
M. Raemaekers; Douwe P. Bergsma; Richard J. A. Wezel; G. J. Wildt; Albert V. Berg In: Journal of Neurophysiology, vol. 105, no. 2, pp. 872–882, 2011. @article{Raemaekers2011, Cerebral blindness is a loss of vision as a result of postchiasmatic damage to the visual pathways. Parts of the lost visual field can be restored through training. However, the neuronal mechanisms through which training effects occur are still unclear. We therefore assessed training-induced changes in brain function in eight patients with cerebral blindness. Visual fields were measured with perimetry and retinotopic maps were acquired with functional magnetic resonance imaging (fMRI) before and after vision restoration training. We assessed differences in hemodynamic responses between sessions that represented changes in amplitudes of neural responses and changes in receptive field locations and sizes. Perimetry results showed highly varied visual field recovery with shifts of the central visual field border ranging between 1 and 7°. fMRI results showed that, although retinotopic maps were mostly stable over sessions, there was a small shift of receptive field locations toward a higher eccentricity after training in addition to increases in receptive field sizes. In patients with bilateral brain activation, these effects were stronger in the affected than in the intact hemisphere. Changes in receptive field size and location could account for limited visual field recovery (± 1°), although it could not account for the large increases in visual field size that were observed in some patients. Furthermore, the retinotopic maps strongly matched perimetry measurements before training. These results are taken to indicate that local visual field enlargements are caused by receptive field changes in early visual cortex, whereas large-scale improvement cannot be explained by this mechanism. |
Benedikt Reuter; David Möllers; Julia Bender; Asysa Schwehn; Juliane Ziemek; Jürgen Gallinat; Norbert Kathmann Volitional saccades and attentional mechanisms in schizophrenia patients and healthy control subjects Journal Article In: Psychophysiology, vol. 48, no. 10, pp. 1333–1339, 2011. @article{Reuter2011, Schizophrenia (SZ) patients showed increased volitional saccade latencies, suggesting deficient volitional initiation of action. Yet increased volitional saccade latencies may also result from deficits in attention shifts. To dissociate attention shifting and saccade initiation, we asked 25 SZ patients and 25 healthy subjects to make saccades toward newly appearing (onset) targets and toward the loci of disappearing (offset) targets. Similar onsets and offsets were also used as attention cues in a Posner-type manual task. As expected, onsets and offsets had similar effects on attention. In contrast, saccade latencies were considerably longer with offset compared to onset targets, reflecting additional time for volitional saccade initiation. Unexpectedly, SZ patients had normal saccade latencies. Presumably, the expected deficit was compensated by decreased fixation-related neural activity, which was induced by the disappearance of fixation stimuli. |
Anil Kumar; Irene Gottlob; Rebecca J. Mclean; Shery Thomas; Mervyn G. Thomas; Frank A. Proudlock Clinical and oculomotor characteristics of albinism compared to FRMD7 associated infantile nystagmus Journal Article In: Investigative Ophthalmology & Visual Science, vol. 52, no. 5, pp. 2306–2313, 2011. @article{Kumar2011, PURPOSE. Previous studies have found no difference between nystagmus characteristics associated with idiopathic infantile nystagmus (IIN) and that associated with albinism. The present aim is to compare the oculomotor characteristics and other associated clinical features of albinism and a genetically homogenous group of IIN volunteers where the nystagmus is associated with FRMD7 mutations. METHODS. Oculomotor characteristics and related clinical features between albinism (n ⫽ 52) and idiopathic nystag- mus associated with FRMD7 mutations (FRMD7-IIN |
Georgia Laretzaki; Sotiris Plainis; Ioannis Vrettos; Anna Chrisoulakis; Ioannis G. Pallikaris; Panos Bitsios Threat and trait anxiety affect stability of gaze fixation Journal Article In: Biological Psychology, vol. 86, no. 3, pp. 330–336, 2011. @article{Laretzaki2011, Threat accelerates early visual information processing, as shown by shorter P100 latencies of pattern Visual Evoked Potentials in subjects with low trait anxiety, but the opposite is true for high anxious subjects. We sought to determine if, and how, threat and trait anxiety interact to affect stability of gaze fixation. We used video oculography to record gaze position in the presence and in the absence of a fixational stimulus, in a safe and a verbal threat condition in subjects characterised for their trait anxiety. Trait anxiety significantly predicted fixational instability in the threat condition. An extreme tertile analysis revealed that fixation was less stable in the high anxiety group, especially under threat or in the absence of a stimulus. The effects of anxiety extend to perceptual and sensorimotor processes. These results have implications for the understanding of individual differences in occulomotor planning and visually guided behavior. |
Jiyeon Lee; Cynthia K. Thompson Real-time production of unergative and unaccusative sentences in normal and agrammatic speakers: An eyetracking study Journal Article In: Aphasiology, vol. 25, no. 6-7, pp. 813–825, 2011. @article{Lee2011a, Background: Speakers with agrammatic aphasia have greater difficulty producing unaccusative (float) compared to unergative (bark) verbs (Kegl, 1995; Lee & Thompson, 2004; Thompson, 2003), putatively because the former involve movement of the theme to the subject position from the post-verbal position, and are therefore more complex than the latter (Burzio, 1986; Perlmutter, 1978). However, it is unclear if and how sentence production processes are affected by the linguistic distinction between these two types of verbs in normal and impaired speakers. Aims: This study examined real-time production of sentences with unergative (the black dog is barking) vs unaccusative (the black tube is floating) verbs in healthy young speakers and individuals with agrammatic aphasia, using eyetracking. Methods & Procedures: Participants' eye movements and speech were recorded while they produced a sentence using computer displayed written stimuli (e.g., black, dog, is barking). Outcomes & Results: Both groups of speakers produced numerically fewer unaccusative sentences than unergative sentences. However, the eye movement data revealed significant differences in fixations between the adjective (black) vs the noun (tube) when producing unaccusatives, but not when producing unergatives for both groups. Interestingly, whereas healthy speakers showed this difference during speech, speakers with agrammatism showed this difference prior to speech onset. Conclusions: These findings suggest that the human sentence production system differentially processes unaccusatives vs unergatives. This distinction is preserved in individuals with agrammatism; however, the time course of sentence planning appears to differ from healthy speakers (Lee & Thompson, 2010). |
Ningdong Li; Xiajuan Wang; Yuchuan Wang; Liming Wang; Ming Ying; Ruifang Han; Yuyan Liu; Kanxing Zhao Investigation of the gene mutations in two Chinese families with X-linked infantile nystagmus Journal Article In: Molecular Vision, vol. 17, pp. 461–468, 2011. @article{Li2011, Purpose: To identify the gene mutations causing X-linked infantile nystagmus in two Chinese families (NYS003 and NYS008), of which the NYS003 family was assigned to the FERM domain–containing 7 (FRMD7) gene linked region in our previous study, and no mutations were found by direct sequencing. Methods: Two microsatellites, DXS1047 and DXS1001, were amplified using a PCR reaction for the linkage study in the NYS008 family. FRMD7 was sequenced and mutations were analyzed. Multiplex ligation-dependent probe amplification (MLPA) was used to detect FRMD7 mutations in the NYS003 family. Results: The NYS008 family yielded a maximum logarithm of odds (LOD) score of 1.91 at θ=0 with DXS1001. FRMD7 sequencing showed a nucleotide change of c. 623A>G in exon7 of the patients' FRMD7 gene, which was predicted to result in an H208R amino acid change. This novel mutation was absent in 100 normal Han Chinese controls. No FRMD7 gene mutations were detected by MLPA in the NYS003 family. Conclusions: We identified a novel mutation, c. 623A>G (p. H208R), in a Han Chinese family with infantile nystagmus. This mutation expands the mutation spectrum of FRMD7 and contributes to the research on the molecular pathogenesis of FRMD7. |
Antonio F. Macedo; Michael D. Crossland; Gary S. Rubin Investigating unstable fixation in patients with macular disease Journal Article In: Investigative Ophthalmology & Visual Science, vol. 52, no. 3, pp. 1275–1280, 2011. @article{Macedo2011, PURPOSE. To assess the effect on visual acuity of compensating fixation instability by controlling retinal image motion in people with macular disease. METHODS. Ten patients with macular disease participated in this study. Crowded and noncrowded visual acuity were measured using an eye tracking system to compensate for fixation instability. Four conditions, corresponding to four levels of retinal image motion, were tested: no compensation (normal motion), partial compensation (reduced motion), total compensation (no motion), and overcompensation (increased motion). Fixation stability and the number of preferred retinal loci were also measured. RESULTS. Modulating retinal image motion had the same effect on crowded and noncrowded visual acuity (P ⫽ 0.601). When fixation instability was overcompensated, acuity worsened by 0.1 logMAR units (P ⬍ 0.001) compared with baseline (no compensation) and remained equal to baseline for all other conditions. CONCLUSIONS. In people with macular disease, retinal image motion caused by fixation instability does not reduce either crowded or noncrowded visual acuity. Acuity declines when fixation instability is overcompensated, showing limited tolerance to increased retinal image motion. The results provide evidence that fixation instability does not improve visual acuity and may be a consequence of poor oculomotor control. |
Kathryn L. McCabe; Dominique Rich; Carmel M. Loughland; Ulrich Schall; Linda E. Campbell Visual scanpath abnormalities in 22q11.2 deletion syndrome: Is this a face specific deficit? Journal Article In: Psychiatry Research, vol. 189, no. 2, pp. 292–298, 2011. @article{McCabe2011, People with 22q11.2 deletion syndrome (22q11DS) have deficits in face emotion recognition. However, it is not known whether this is a deficit specific to faces, or represents maladaptive information processing strategies to complex stimuli in general. This study examined the specificity of face emotion processing deficits in 22q11DS by exploring recognition accuracy and visual scanpath performance to a Faces task compared to a Weather Scene task. Seventeen adolescents with 22q11DS (11. =females |
Tom Foulsham; Jason J. S. Barton; Alan Kingstone; Richard Dewhurst; Geoffrey Underwood Modeling eye movements in visual agnosia with a saliency map approach: Bottom-up guidance or top-down strategy? Journal Article In: Neural Networks, vol. 24, no. 6, pp. 665–677, 2011. @article{Foulsham2011, Two recent papers (Foulsham, Barton, Kingstone, Dewhurst, & Underwood, 2009; Mannan, Kennard, & Husain, 2009) report that neuropsychological patients with a profound object recognition problem (visual agnosic subjects) show differences from healthy observers in the way their eye movements are controlled when looking at images. The interpretation of these papers is that eye movements can be modeled as the selection of points on a saliency map, and that agnosic subjects show an increased reliance on visual saliency, i.e., brightness and contrast in low-level stimulus features. Here we review this approach and present new data from our own experiments with an agnosic patient that quantifies the relationship between saliency and fixation location. In addition, we consider whether the perceptual difficulties of individual patients might be modeled by selectively weighting the different features involved in a saliency map. Our data indicate that saliency is not always a good predictor of fixation in agnosia: even for our agnosic subject, as for normal observers, the saliency-fixation relationship varied as a function of the task. This means that top-down processes still have a significant effect on the earliest stages of scanning in the setting of visual agnosia, indicating severe limitations for the saliency map model. Top-down, active strategies-which are the hallmark of our human visual system-play a vital role in eye movement control, whether we know what we are looking at or not. |
Teresa C. Frohman; Scott L. Davis; Elliot M. Frohman Modeling the mechanisms of Uhthoff's phenomenon in MS patients with internuclear ophthalmoparesis Journal Article In: Annals of the New York Academy of Sciences, vol. 1233, no. 1, pp. 313–319, 2011. @article{Frohman2011, Internuclear ophthalmoparesis (INO) is the most common saccadic eye movement disorder observed in patients with multiple sclerosis (MS). It is characterized by slowing of the adducting eye during horizontal saccades, and most commonly results from a demyelinating lesion in the medial longitudinal fasciculus (MLF) within the midline tegmentum of the pons (ventral to the fourth ventricle) or midbrain (ventral to the cerebral aqueduct). Recent research has demonstrated that adduction velocity in MS-related INO, as measured by infrared eye movement recording techniques, is further reduced by a systematic increase in core body temperature (utilizing tube-lined water infusion suits in conjunction with an ingestible temperature probe and transabdominal telemetry) and reversed to baseline with active cooling. These results suggest that INO may represent a model syndrome by which we can carefully study the Uhthoff's phenomenon and objectively test therapeutic agents for its prevention. |
Andreas Hartwig; W. Neil Charman; Hema Radhakrishnan Accommodative response to peripheral stimuli in myopes and emmetropes Journal Article In: Ophthalmic and Physiological Optics, vol. 31, no. 1, pp. 91–99, 2011. @article{Hartwig2011, Purpose: It has been suggested that peripheral refractive error may influence eye growth and the development of axial refractive error, implying that the peripheral retina is sensitive to defocus. This study aimed to evaluate the steady-state accommodative response to peripheral stimuli in 10 young, adult myopes (mean spherical equivalent error -2.10 ± 1.72 D, median -1.63 D, range -0.83 to -6.00 D) and 10 emmetropes (mean spherical equivalent error -0.02 ± 0.35 D, median +0.08 D, range -0.50 to +0.50 D). Methods: The subjects were asked to view monocularly the centre of a screen displaying each of a series of eccentric accommodative targets placed at 5, 10 and 15°. An axial target was viewed for comparison purposes. Accommodation was measured using an open-field autorefractor, each stimulus being varied between about 0 and 4 D with spherical trial lenses placed in front of the viewing eye. Results: The results confirm that the peripheral retina is sensitive to optical focus, up to field angles of at least 15°, with accommodative responses weakening as the peripheral angle increases. There is some evidence that peripheral accommodation may be less effective in myopes than emmetropes. Conclusions: Although peripheral accommodation can be demonstrated in the absence of a central stimulus, the accommodation response is normally dominated by the central stimulus and it seems unlikely that peripheral accommodation effects play an important role in refractive development. |
Andreas Hartwig; Emma Gowen; W. Neil Charman; Hema Radhakrishnan Analysis of head position used by myopes and emmetropes when performing a near-vision reading task Journal Article In: Vision Research, vol. 51, no. 14, pp. 1712–1717, 2011. @article{Hartwig2011b, The aim of the study was to compare head posture in young, adult emmetropes and corrected myopes during a reading task. Thirty-two (32) myopes (mean spherical equivalent: -3.46 ± 2.35. D) and 22 emmetropes (mean spherical equivalent: -0.03 ± 0.36. D) participated in the study. Of the myopes, 16 were progressing (rate of progression ≥-0.5. D over the previous 2. years), 12 were stable (changes of -0.25. D or less over 2. years) and four could not be classified. Seated subjects were asked to read a text binocularly in their habitual posture. To measure head posture, two simultaneous images were recorded from different directions. In a separate study with the same subjects and conditions, a motion monitor was used to track head posture for 1. min. The habitual reading distance was measured in both studies, together with the stereoscopic acuity and fixation disparity for each subject.The results of the photographic study showed no significant differences in head posture or reading distance between the myopic and emmetropic groups (p>0.05) but there was some evidence that downward pitch angles were greater in progressing myopes than in non-progressing myopes (p=0.03). No correlations were observed between the binocular parameters and head posture. Reading distances were systematically shorter with the helmet-mounted eye tracker and it was concluded that posture was affected by the weight of the equipment. With this reservation, it appeared that the rate of change of downward pitch angle over the 1-min recording session increased with the subject's rate of myopia progression (correlation between myopia progression and slope of pitch: r2=-0.69 |
Richard W. Hertle; Dongsheng Yang; Kenneth Adams; Roxanne Caterino Surgery for the treatment of vertical head posturing associated with infantile nystagmus syndrome: Results in 24 patients Journal Article In: Clinical and Experimental Ophthalmology, vol. 39, no. 1, pp. 37–46, 2011. @article{Hertle2011, Background: The study of the clinical and electrophysiological effects of eye muscle surgery on patients with infantile nystagmus has broadened our knowledge of the disease and its interventions. Design: Prospective, comparative, interventional case series. Participants: Twenty-four patients with a vertical head posture because of electrophysiologically diagnosed infantile nystagmus syndrome. The ages ranged from 2.5 to 38 years and follow up averaged 14.0 months. Methods: Thirteen patients with a chin-down posture had a bilateral superior rectus recession, inferior oblique myectomy and a horizontal rectus recession or tenotomy. Those 11 with a chin-up posture had a bilateral superior oblique tenectomy, inferior rectus recession and a horizontal rectus recession or tenotomy. Main Outcome Measures: Outcome measures included: demography, eye/systemic conditions and preoperative and postoperative; binocular, best optically corrected, null zone acuity, head posture, null zone foveation time and nystagmus waveform changes. Results: Associated conditions were strabismus in 66%, ametropia in 96%, amblyopia in 46% and optic nerve, foveal dysplasia or albinism in 54%. Null zone acuity increased at least 0.1 logMAR in 20 patients (P < 0.05 group mean change). Patients had significant (P < 0.05) improvements in degrees of head posture, average foveation time in milliseconds and infantile nystagmus syndrome waveform improvements. Conclusions: This study illustrates a successful surgical approach to treatment and provides expectations of ocular motor and visual results after vertical head posture surgery because of an eccentric gaze null in patients with infantile nystagmus syndrome. |
Elina Birmingham; Moran Cerf; Ralph Adolphs Comparing social attention in autism and amygdala lesions: Effects of stimulus and task condition Journal Article In: Social Neuroscience, vol. 6, no. 5-6, pp. 420–435, 2011. @article{Birmingham2011, The amygdala plays a critical role in orienting gaze and attention to socially salient stimuli. Previous work has demonstrated that SM a patient with rare bilateral amygdala lesions, fails to fixate and make use of information from the eyes in faces. Amygdala dysfunction has also been implicated as a contributing factor in autism spectrum disorders (ASD), consistent with some reports of reduced eye fixations in ASD. Yet, detailed comparisons between ASD and patients with amygdala lesions have not been undertaken. Here we carried out such a comparison, using eye tracking to complex social scenes that contained faces. We presented participants with three task conditions. In the Neutral task, participants had to determine what kind of room the scene took place in. In the Describe task, participants described the scene. In the Social Attention task, participants inferred where people in the scene were directing their attention. SM spent less time looking at the eyes and much more time looking at the mouths than control subjects, consistent with earlier findings. There was also a trend for the ASD group to spend less time on the eyes, although this depended on the particular image and task. Whereas controls and SM looked more at the eyes when the task required social attention, the ASD group did not. This pattern of impairments suggests that SM looks less at the eyes because of a failure in stimulus-driven attention to social features, whereas individuals with ASD look less at the eyes because they are generally insensitive to socially relevant information and fail to modulate attention as a function of task demands. We conclude that the source of the social attention impairment in ASD may arise upstream from the amygdala, rather than in the amygdala itself. |
Dario Cazzoli; Thomas Nyffeler; Christian W. Hess; René M. Müri Vertical bias in neglect: A question of time? Journal Article In: Neuropsychologia, vol. 49, no. 9, pp. 2369–2374, 2011. @article{Cazzoli2011, Neglect is defined as the failure to attend and to orient to the contralesional side of space. A horizontal bias towards the right visual field is a classical finding in patients who suffered from a right-hemispheric stroke. The vertical dimension of spatial attention orienting has only sparsely been investigated so far. The aim of this study was to investigate the specificity of this vertical bias by means of a search task, which taps a more pronounced top-down attentional component. Eye movements and behavioural search performance were measured in thirteen patients with left-sided neglect after right hemispheric stroke and in thirteen age-matched controls. Concerning behavioural performance, patients found significantly less targets than healthy controls in both the upper and lower left quadrant. However, when targets were located in the lower left quadrant, patients needed more visual fixations (and therefore longer search time) to find them, suggesting a time-dependent vertical bias. |
Jason H. Wong; Matthew S. Peterson The interaction between memorized objects and abrupt onsets in oculomotor capture Journal Article In: Attention, Perception, and Psychophysics, vol. 73, no. 6, pp. 1768–1779, 2011. @article{Wong2011, Recent evidence has been found for a source of task-irrelevant oculomotor capture (defined as when a salient event draws the eyes away from a primary task) that originates from working memory. An object memorized for a nonsearch task can capture the eyes during search. Here, an experiment was conducted that generated interactions between the presence of a memorized object (a colored disk) with the abrupt onset of a new object during visual search. The goal was to compare memory-driven oculomotor capture to oculomotor capture caused by an abrupt onset. This has implications for saccade programming theories, which have little to say about saccades that are influenced by object working memory. Results showed that memorized objects capture the eyes at nearly the same rate as abrupt onsets. When the abrupt onset and a memorized color coincide in the same object, this combination leads to even greater oculomotor capture. Finally, latencies support the competitive integration model: Shorter saccade latencies were found when the memorized color combined with the onset captured the eyes, as compared to either color or onset only. Longer latencies were also found when the color and onset occurred in the same display but were spatially separated. |
Eckart Zimmermann; David C. Burr; M. Concetta Morrone Spatiotopic visual maps revealed by saccadic adaptation in humans Journal Article In: Current Biology, vol. 21, no. 16, pp. 1380–1384, 2011. @article{Zimmermann2011, Saccadic adaptation [1] is a powerful experimental paradigm to probe the mechanisms of eye movement control and spatial vision, in which saccadic amplitudes change in response to false visual feedback. The adaptation occurs primarily in the motor system [2, 3], but there is also evidence for visual adaptation, depending on the size and the permanence of the postsaccadic error [4-7]. Here we confirm that adaptation has a strong visual component and show that the visual component of the adaptation is spatially selective in external, not retinal coordinates. Subjects performed a memory-guided, double-saccade, outward-adaptation task designed to maximize visual adaptation and to dissociate the visual and motor corrections. When the memorized saccadic target was in the same position (in external space) as that used in the adaptation training, saccade targeting was strongly influenced by adaptation (even if not matched in retinal or cranial position), but when in the same retinal or cranial but different external spatial position, targeting was unaffected by adaptation, demonstrating unequivocal spatiotopic selectivity. These results point to the existence of a spatiotopic neural representation for eye movement control that adapts in response to saccade error signals. |
Marc Zirnsak; R. G. K. Gerhards; Roozbeh Kiani; Markus Lappe; Fred H. Hamker Anticipatory saccade target processing and the presaccadic transfer of visual features Journal Article In: Journal of Neuroscience, vol. 31, no. 49, pp. 17887–17891, 2011. @article{Zirnsak2011, As we shift our gaze to explore the visual world, information enters cortex in a sequence of successive snapshots, interrupted by phases of blur. Our experience, in contrast, appears like a movie of a continuous stream of objects embedded in a stable world. This perception of stability across eye movements has been linked to changes in spatial sensitivity of visual neurons anticipating the upcoming saccade, often referred to as shifting receptive fields (Duhamel et al., 1992; Walker et al., 1995; Umeno and Goldberg, 1997; Nakamura and Colby, 2002). How exactly these receptive field dynamics contribute to perceptual stability is currently not clear. Anticipatory receptive field shifts toward the future, postsaccadic position may bridge the transient perisaccadic epoch (Sommer and Wurtz, 2006; Wurtz, 2008; Melcher and Colby, 2008). Alternatively, a presaccadic shift of receptive fields toward the saccade target area (Tolias et al., 2001) may serve to focus visual resources onto the most relevant objects in the postsaccadic scene (Hamker et al., 2008). In this view, shifts of feature detectors serve to facilitate the processing of the peripheral visual content before it is foveated. While this conception is consistent with previous observations on receptive field dynamics and on perisaccadic compression (Ross et al., 1997; Morrone et al., 1997; Kaiser and Lappe, 2004), it predicts that receptive fields beyond the saccade target shift toward the saccade target rather than in the direction of the saccade. We have tested this prediction in human observers via the presaccadic transfer of the tilt-aftereffect (Melcher, 2007). |
Sarim Mohammad; Irene Gottlob; Anil Kumar; Mervyn G. Thomas; Christopher Degg; Viral Sheth; Frank A. Proudlock The functional significance of foveal abnormalities in albinism measured using spectral-domain optical coherence tomography Journal Article In: Ophthalmology, vol. 118, no. 8, pp. 1645–1652, 2011. @article{Mohammad2011, Purpose: The relationship between foveal abnormalities in albinism and best-corrected visual acuity (BCVA) is unclear. High-resolution spectral-domain optical coherence tomography (SD OCT) was used to quantify foveal retinal layer thicknesses and to assess the functional significance of foveal morphologic features in patients with albinism. Design: Cross-sectional study. Participants: Forty-seven patients with albinism and 20 healthy control volunteers were recruited to the study. Methods: Using high-resolution SD OCT, 7×7×2-mm volumetric scans of the fovea were acquired (3-μm axial resolution). The B scan nearest the center of the fovea was identified using signs of foveal development. The thickness of each retinal layer at the fovea and foveal pit depth were quantified manually using ImageJ software and were compared with BCVA. Main Outcome Measures: Total retinal thickness, foveal pit depth, photoreceptor layer thickness, and processing layer thickness in relation to BCVA. Results: Total photoreceptor layer thickness at the fovea was correlated highly to BCVA (P = 0.0008; r = 0.501). Of the photoreceptor layers, the outer segment length was correlated most strongly to BCVA (P<0.0001; r = 0.641). In contrast, there was no significant correlation between either total retinal thickness or pit depth and BCVA (P>0.05). This was because of an inverse correlation between total photoreceptor layer thickness and total processing layer thickness (P<0.0001; r = 0.696). Conclusions: Neither the total retinal thickness nor the pit depth are reliable indicators of visual deficit, because patients with similar overall retinal thickness had widely varying foveal morphologic features. In albinism, the size of the photoreceptor outer segment was found to be the strongest predictor of BCVA. These results suggest that detailed SD OCT images of photoreceptor anatomic features provide a useful tool in assessing the visual potential in patients with albinism. |
Alexander C. Schütz Motion transparency: Depth ordering and smooth pursuit eye movements Journal Article In: Journal of Vision, vol. 11, no. 14, pp. 1–19, 2011. @article{Schuetz2011, When two overlapping, transparent surfaces move in different directions, there is ambiguity with respect to the depth ordering of the surfaces. Little is known about the surface features that are used to resolve this ambiguity. Here, we investigated the influence of different surface features on the perceived depth order and the direction of smooth pursuit eye movements. Surfaces containing more dots, moving opposite to an adapted direction, moving at a slower speed, or moving in the same direction as the eyes were more likely to be seen in the back. Smooth pursuit eye movements showed an initial preference for surfaces containing more dots, moving in a non-adapted direction, moving at a faster speed, and being composed of larger dots. After 300 to 500 ms, smooth pursuit eye movements adjusted to perception and followed the surface whose direction had to be indicated. The differences between perceived depth order and initial pursuit preferences and the slow adjustment of pursuit indicate that perceived depth order is not determined solely by the eye movements. The common effect of dot number and motion adaptation suggests that global motion strength can induce a bias to perceive the stronger motion in the back. |
Alexander C. Schütz; David Souto Adaptation of catch-up saccades during the initiation of smooth pursuit eye movements Journal Article In: Experimental Brain Research, vol. 209, no. 4, pp. 537–549, 2011. @article{Schuetz2011a, Reduction of retinal speed and alignment of the line of sight are believed to be the respective primary functions of smooth pursuit and saccadic eye movements. As the eye muscles strength can change in the short-term, continuous adjustments of motor signals are required to achieve constant accuracy. While adaptation of saccade amplitude to systematic position errors has been extensively studied, we know less about the adaptive response to position errors during smooth pursuit initiation, when target motion has to be taken into account to program saccades, and when position errors at the saccade endpoint could also be corrected by increasing pursuit velocity. To study short-term adaptation (250 adaptation trials) of tracking eye movements, we introduced a position error during the first catch-up saccade made during the initiation of smooth pursuit-in a ramp-step-ramp paradigm. The target position was either shifted in the direction of the horizontally moving target (forward step), against it (backward step) or orthogonally to it (vertical step). Results indicate adaptation of catch-up saccade amplitude to back and forward steps. With vertical steps, saccades became oblique, by an inflexion of the early or late saccade trajectory. With a similar time course, post-saccadic pursuit velocity was increased in the step direction, adding further evidence that under some conditions pursuit and saccades can act synergistically to reduce position errors. |
Petra Sinn; Ralf Engbert Saccadic facilitation by modulation of microsaccades in natural backgrounds Journal Article In: Attention, Perception, and Psychophysics, vol. 73, no. 4, pp. 1029–1033, 2011. @article{Sinn2011, Saccades move objects of interest into the center of the visual field for high-acuity visual analysis. White, Stritzke, and Gegenfurtner (Current Biology, 18, 124-128, 2008) have shown that saccadic latencies in the context of a structured background are much shorter than those with an unstructured background at equal levels of visibility. This effect has been explained by possible preactivation of the saccadic circuitry whenever a structured background acts as a mask for potential saccade targets. Here, we show that background textures modulate rates of microsaccades during visual fixation. First, after a display change, structured backgrounds induce a stronger decrease of microsaccade rates than do uniform backgrounds. Second, we demonstrate that the occurrence of a microsaccade in a critical time window can delay a subsequent saccadic response. Taken together, our findings suggest that microsaccades contribute to the saccadic facilitation effect, due to a modulation of microsaccade rates by properties of the background. |
Miriam Spering; Alexander C. Schütz; Doris I. Braun; Karl R. Gegenfurtner Keep your eyes on the ball: Smooth pursuit eye movements enhance prediction of visual motion Journal Article In: Journal of Neurophysiology, vol. 105, no. 4, pp. 1756–1767, 2011. @article{Spering2011a, Success of motor behavior often depends on the ability to predict the path of moving objects. Here we asked whether tracking a visual object with smooth pursuit eye movements helps to predict its motion direction. We developed a paradigm, "eye soccer," in which observers had to either track or fixate a visual target (ball) and judge whether it would have hit or missed a stationary vertical line segment (goal). Ball and goal were presented briefly for 100-500 ms and disappeared from the screen together before the perceptual judgment was prompted. In pursuit conditions, the ball moved towards the goal; in fixation conditions, the goal moved towards the stationary ball, resulting in similar retinal stimulation during pursuit and fixation. We also tested the condition in which the goal was fixated and the ball moved. Motion direction prediction was significantly better in pursuit than in fixation trials, regardless of whether ball or goal served as fixation target. In both fixation and pursuit trials, prediction performance was better when eye movements were accurate. Performance also increased with shorter ball-goal distance and longer presentation duration. A longer trajectory did not affect performance. During pursuit, an efference copy signal might provide additional motion information, leading to the advantage in motion prediction. |
Andreas Sprenger; Peter Trillenberg; Jonas Pohlmann; Kirsten Herold; Rebekka Lencer; Christoph Helmchen The role of prediction and anticipation on age-related effects on smooth pursuit eye movements Journal Article In: Annals of the New York Academy of Sciences, vol. 1233, pp. 168–176, 2011. @article{Sprenger2011, Externally guided sensory-motor processes deteriorate with increasing age. Internally guided, for example, predictive, behavior usually helps to overcome sensory-motor delays. We studied whether predictive components of visuomotor transformation decline with age. We investigated smooth pursuit eye movements (SPEM) of 45 healthy subjects with paradigms of different degrees of predictability with respect to target motion onset, type (smoothed triangular, ramp stimulation), and direction by blanking the target at various intervals of the ramp stimulation. Using repetitive trials of SPEM stimulation, we could dissociate anticipatory and predictive components of extraretinal smooth pursuit behavior. The main results suggest that basic motor parameters decline with increasing age, whereas both anticipation and prediction of target motion did not change with age. We suggest that the elderly maintain their capability of using prediction in the immediate control of motor behavior, which might be a way to compensate for age-related delays in sensory-motor transformation, even in the absence of sensory signals. |
Aiga Švede; Jörg Hoormann; Stephanie Jainta; Wolfgang Jaschinski Subjective fixation disparity affected by dynamic asymmetry, resting vergence, and nonius bias Journal Article In: Investigative Ophthalmology & Visual Science, vol. 52, no. 7, pp. 4356–4361, 2011. @article{Svede2011, PURPOSE. This study was undertaken to investigate how sub- jectively measured fixation disparity can be explained by (1) the convergent–divergent asymmetry of vergence dynamics (called dynamic asymmetry) for a disparity vergence step stimulus of 1° (60 arc min), (2) the dark vergence, and (3) the nonius bias. METHODS. Fixation disparity, dark vergence, and nonius bias were measured subjectively using nonius lines. Dynamic vergence step responses (both convergent and divergent) were measured objectively. RESULTS. In 20 subjects (mean age, 24.5 ⫾ 4.3 years, visual acuity, ≥1.0; all emmetropic except for one with myopia, wearing contact lenses), multiple regression analyses showed that 39% of the variance in subjective fixation disparity was due to the characteristic factors of physiological vergence: dynamic asymmetry (calculated from convergent and divergent veloci- ties), and dark vergence. An additional 23% of variance was due to the subjective nonius bias (i.e., the physical nonius offset required for perceived alignment of binocularly [nondichopti- cally] presented nonius lines). Together, these factors ex- plained 62% of the interindividual differences in subjectively measured fixation disparity, demonstrating the influence of oculomotor and perceptual factors. CONCLUSIONS. Clinically relevant subjective fixation disparity originates from distinct physiological sources. Dynamic asym- metry in vergence dynamics, resting vergence, and nonius bias were found to affect fixation disparity directly, not only via changes in vergence dynamics. |
Masahiko Terao; Ikuya Murakami Compensation for equiluminant color motion during smooth pursuit eye movement Journal Article In: Journal of Vision, vol. 11, no. 6, pp. 1–12, 2011. @article{Terao2011, Motion perception is compromised at equiluminance. Because previous investigations have been primarily carried out under fixation conditions, it remains unknown whether and how equiluminant color motion comes into play in the velocity compensation for retinal image motion due to smooth pursuit eye movement. We measured the retinal image velocity required to reach subjective stationarity for a horizontally drifting sinusoidal grating in the presence of horizontal smooth pursuit. The grating was defined by luminance or chromatic modulation. When the subjective stationarity of the color motion was shifted toward environmental stationarity, compared with the subjective stationarity of luminance motion, that of color motion was farther from retinal stationarity, indicating that a slowing of color motion occurred before this factor contributed to the process by which retinal motion was integrated with a biological estimate of eye velocity during pursuit. The gain in the estimate of eye velocity per se was unchanged irrespective of whether the stimulus was defined by luminance or by color. Indeed, the subjective reduction in the speed of color motion during fixation was accounted for by the same amount of deterioration in speed. From these results, we conclude that the motion deterioration at equiluminance takes place prior to the velocity comparison. |
Stefan Van der Stigchel; Jelmer P. De Vries; R. Bethlehem; Jan Theeuwes A global effect of capture saccades Journal Article In: Experimental Brain Research, vol. 210, no. 1, pp. 57–65, 2011. @article{VanderStigchel2011, When two target elements are presented in close proximity, the endpoint of a saccade is generally positioned at an intermediate location ('global effect'). Here, we investigated whether the global effect also occurs for eye movements executed to distracting elements. To this end, we adapted the oculomotor capture paradigm such that on a subset of trials, two distractors were presented. When the two distractors were closely aligned, erroneous eye movements were initiated to a location in between the two distractors. Even though to a lesser extent, this effect was also present when the two distractors were presented further apart. In a second experiment, we investigated the global effect for eye movements in the presence of two targets. A strong global effect was observed when two targets were presented closely aligned, while this effect was absent when the targets were further apart. This study shows that there is a global effect when saccades are captured by distractors. This 'capture global' effect is different from the traditional global effect that occurs when two targets are presented because the global effect of capture saccades also occurs for remote elements. The spatial dynamics of this global effect will be explained in terms of the population coding theory. |
Sara A. Winges; John F. Soechting Spatial and temporal aspects of cognitive influences on smooth pursuit Journal Article In: Experimental Brain Research, vol. 211, no. 1, pp. 27–36, 2011. @article{Winges2011, It is well known that prediction is used to overcome processing delays within the motor system and ocular control is no exception. Motion extrapolation is one mechanism that can be used to overcome the visual processing delay. Expectations based on previous experience or cognitive cues are also capable of overcoming this delay. The present experiment was designed to examine how smooth pursuit is altered by cognitive information about the time and/or direction of an upcoming change in target direction. Subjects visually tracked a cursor as it moved at a constant velocity on a computer screen. The target initially moved from left to right and then abruptly reversed horizontal direction and traveled along one of seven possible oblique paths. In half of the trials, a cue was present throughout the trial to signal the position (as well as the time), and/or the direction of the upcoming change. Whenever a position cue (which will be referred to as a timing cue throughout the paper) was present, there were clear anticipatory adjustments to the horizontal velocity component of smooth pursuit. In the presence of a timing cue, a directional cue also led to anticipatory adjustments in the vertical velocity, and hence the direction of smooth pursuit. However, without the timing cue, a directional cue alone produced no anticipation. Thus, in this task, a cognitive spatial cue about the new direction could not be used unless it was made explicit in the time domain. |
Nhung X. Nguyen; Andrea Stockum; Gesa A. Hahn; Susanne Trauzettel-Klosinski Training to improve reading speed in patients with juvenile macular dystrophy: A randomized study comparing two training methods Journal Article In: Acta Ophthalmologica, vol. 89, no. 1, pp. 82–88, 2011. @article{Nguyen2011, Purpose: In this study, we examined the clinical application of two training methods for optimizing reading ability in patients with juvenile macular dystrophy with established eccentric preferred reti- nal locus and optimal use of low-vision aids. Method: This randomized study included 36 patients with juvenile macular dystrophy (35 with Stargardt's disease and one with Best's disease). All patients have been using individually opti- mized low-vision aids. After careful ophthalmological examination, patients were randomized into two groups: Group 1: Training to read during rapid serial visual presentation (RSVP) with elimination of eye movements as far as possible (n = 20); Group 2: Training to optimize reading eye movements (SM, sensomotoric training) (n = 16). Only patients with magnification requirement up to sixfold were included in the study. Training was performed for 4 weeks with an intensity of ½ hr per day and 5 days a week. Reading speed during page reading was measured before and after training. Eye movements during silent reading were recorded before and after training using a video eye tracker in 11 patients (five patients of SM and six of RSVP training group) and using an infrared reflection system in five patients (three patients from the SM and two patients of RSVP training group). Results: Age, visual acuity and magnification requirement did not differ significantly between the two groups. The median reading speed was 83 words per minute (wpm) (interquartile range 74–105 wpm) in the RSVP training group and 102 (interquartile range 63–126 wpm) in the SM group before training and increased significantly to 104 (interquartile range 81–124 wpm) and 122, respectively (interquartile range 102–137 wpm; p = 0.01 and 0.006) after training, i.e. patients with RSVP training increased their reading speed by a median of 21 wpm, while it was 20 wpm in the SM group. There were individual patients, who benefited strongly from the training. Eye move- ment recordings before and after training showed that in the RSVP group, increasing reading speed correlated with decreasing fixation duration (r = )0.75 |
Tanja C. W. Nijboer; Gabriela Satris; Stefan Van Stigchel The influence of synesthesia on eye movements: No synesthetic pop-out in an oculomotor target selection task Journal Article In: Consciousness and Cognition, vol. 20, no. 4, pp. 1193–1200, 2011. @article{Nijboer2011, Recent research on grapheme-colour synesthesia has focused on whether visual attention is necessary to induce a synesthetic percept. The current study investigated the influence of synesthesia on overt visual attention during an oculomotor target selection task. Chromatic and achromatic stimuli were presented with one target among distractors (e.g. a '2' (target) among multiple '5's (distractors)). Participants executed an eye movement to the target. Synesthetes and controls showed a comparable target selection performance across conditions and a 'pop-out effect' was only seen in the chromatic condition. As a pop-out effect was absent for the synesthetes in the achromatic condition, a synesthetic element appears not to elicit a synesthetic colour, even when it is the target. The synesthetic percepts are not pre-attentively available to distinguish the synesthetic target from synesthetic distractors when elements are presented in the periphery. Synesthesia appears to require full recognition to bind form and colour. |
Sheena K. Au-Yeung; Valerie Benson; Monica S. Castelhano; Keith Rayner Eye movement sequences during simple versus complex information processing of scenes in autism spectrum disorder Journal Article In: Autism Research and Treatment, vol. 2011, pp. 1–7, 2011. @article{AuYeung2011, Minshew and Goldstein (1998) postulated that autism spectrum disorder (ASD) is a disorder of complex information processing. The current study was designed to investigate this hypothesis. Participants with and without ASD completed two scene perception tasks: a simple “spot the difference” task, where they had to say which one of a pair of pictures had a detail missing, and a complex “which one's weird” task, where they had to decide which one of a pair of pictures looks “weird”. Participants with ASD did not differ from TD participants in their ability to accurately identify the target picture in both tasks. However, analysis of the eye movement sequences showed that participants with ASD viewed scenes differently from normal controls exclusively for the complex task. This difference in eye movement patterns, and the method used to examine different patterns, adds to the knowledge base regarding eye movements and ASD. Our results are in accordance with Minshew and Goldstein's theory that complex, but not simple, information processing is impaired in ASD. |
Sebastian J. Crutch; Manja Lehmann; Nikos Gorgoraptis; Diego Kaski; Natalie Ryan; Masud Husain; Elizabeth K. Warrington Abnormal visual phenomena in posterior cortical atrophy Journal Article In: Neurocase, vol. 17, no. 2, pp. 160–177, 2011. @article{Crutch2011, Individuals with posterior cortical atrophy (PCA) report a host of unusual and poorly explained visual disturbances. This preliminary report describes a single patient (CRO), and documents and investigates abnormally prolonged colour afterimages (concurrent and prolonged perception of colours complimentary to the colour of an observed stimulus), perceived motion of static stimuli, and better reading of small than large letters. We also evaluate CRO's visual and vestibular functions in an effort to understand the origin of her experience of room tilt illusion, a disturbing phenomenon not previously observed in individuals with cortical degenerative disease. These visual symptoms are set in the context of a 4-year longitudinal neuropsychological and neuroimaging investigation of CRO's visual and other cognitive skills. We hypothesise that prolonged colour after-images are attributable to relative sparing of V1 inhibitory interneurons; perceived motion of static stimuli reflects weak magnocellular function; better reading of small than large letters indicates a reduced effective field of vision; and room tilt illusion effects are caused by disordered integration of visual and vestibular information. This study contributes to the growing characterisation of PCA whose atypical early visual symptoms are often heterogeneous and frequently under-recognised. |
Chelsie L. Cushman; Rebecca L. Johnson Age-of-acquisition effects in pure alexia Journal Article In: Quarterly Journal of Experimental Psychology, vol. 64, no. 9, pp. 1726–1742, 2011. @article{Cushman2011, Pure alexia is an acquired reading disorder in which previously literate adults adopt a letter-by-letter processing strategy. Though these individuals display impaired reading, research shows that they are still able to use certain lexical information in order to facilitate visual word processing. The current experiment investigates the role that a word's age of acquisition (AoA) plays in the reading processes of an individual with pure alexia (G.J.) when other lexical variables have been controlled. Results from a sentence reading task in which eye movement patterns were recorded indicated that G.J. shows a strong effect of AoA, where late-acquired words are more difficult to process than early-acquired words. Furthermore, it was observed that the AoA effect is much greater for G.J. than for age-matched control participants. This indicates that patients with pure alexia rely heavily on intact top-down information, supporting the interactive activation model of reading. |
Kirsten A. Dalrymple; Elina Birmingham; Walter F. Bischof; Jason J. S. Barton; Alan Kingstone Opening a window on attention: Documenting and simulating recovery from simultanagnosia Journal Article In: Cortex, vol. 47, no. 7, pp. 787–799, 2011. @article{Dalrymple2011, Simultanagnosia is a disorder of visual attention: the inability to see more than one object at one time. Some hypothesize that this is due to a constriction of the visual " window" of attention. Little is known about how simultanagnosics explore complex stimuli and how their behaviour changes with recovery. We monitored the eye movements of simultanagnosic patient SL to see how she scans social scenes shortly after onset of simultanagnosia (Time 1) and after some recovery (Time 2). At Time 1 SL had an abnormally low proportion of fixations to the eyes of the people in the scenes. She made a significantly larger proportion of fixations to the eyes at Time 2. We hypothesized that this change was related to an expansion of her restricted window of attention. Previously we simulated SL's behaviour in healthy subjects by having them view stimuli through a restricted viewing window. We used this simulation paradigm here to test our expanding window hypothesis. Subjects viewing social scenes through a larger window allocated more fixations to the eyes of people in the scenes than subjects viewing scenes through a smaller window, supporting our hypothesis. Recovery in simultanagnosia may be related to the expansion of the restricted attentional window that characterizes the disorder. |
Louis F. Dell'Osso; Richard W. Hertle; R. John Leigh; Jonathan B. Jacobs; Susan King; Stacia Yaniglos Effects of topical brinzolamide on infantile nystagmus syndrome waveforms: Eyedrops for nystagmus Journal Article In: Journal of Neuro-Ophthalmology, vol. 31, no. 3, pp. 228–233, 2011. @article{DellOsso2011, BACKGROUND: Recent advances in infantile nystagmus syndrome (INS) surgery have uncovered the therapeutic importance of proprioception. In this report, we test the hypothesis that the topical carbonic anhydrase inhibitor (CAI) brinzolamide (Azopt) has beneficial effects on measures of nystagmus foveation quality in a subject with INS. METHODS: Eye movement data were taken, using a high-speed digital video recording system, before and after 3 days of the application of topical brinzolamide 3 times daily in each eye. Nystagmus waveforms were analyzed by applying the eXpanded Nystagmus Acuity Function (NAFX) at different gaze angles and determining the longest foveation domain (LFD) and compared to previously published data from the same subject after the use of a systemic CAI, contact lenses, and convergence and to other subjects before and after eye muscle surgery for INS. RESULTS:: Topical brinzolamide improved foveation by both a 51.9% increase in the peak value of the NAFX function (from 0.395 to 0.600) and a 50% broadening of the NAFX vs Gaze Angle curve (the LFD increased from 20 degrees to 30 degrees ). The improvements in NAFX after topical brinzolamide were equivalent to systemic acetazolamide or eye muscle surgery and were intermediate between those of soft contact lenses or convergence. Topical brinzolamide and contact lenses had equivalent LFD improvements and were less effective than convergence. CONCLUSIONS: In this subject with INS, topical brinzolamide resulted in improved-foveation INS waveforms over a broadened range of gaze angles. Its therapeutic effects were equivalent to systemic CAI. Although a prospective clinical trial is needed to prove efficacy or effectiveness in other subjects, an eyedrops-based therapy for INS may emerge as a viable addition to optical, surgical, behavioral, and systemic drug therapies. |
Joost Felius; Valeria L. N. Fu; Eileen E. Birch; Richard W. Hertle; Reed M. Jost; Vidhya Subramanian Quantifying nystagmus in infants and young children: Relation between foveation and visual acuity deficit Journal Article In: Investigative Ophthalmology & Visual Science, vol. 52, no. 12, pp. 8724–8731, 2011. @article{Felius2011, PURPOSE. Nystagmus eye movement data from infants and young children are often not suitable for advanced quantitative analysis. A method was developed to capture useful informa- tion from noisy data and validate the technique by showing meaningful relationships with visual functioning. METHODS. Horizontal eye movements from patients (age 5 months–8 years) with idiopathic infantile nystagmus syndrome (INS) were used to develop a quantitative outcome measure that allowed for head and body movement during the record- ing. The validity of this outcome was assessed by evaluating its relation to visual acuity deficit in 130 subjects, its relation to actual fixation as assessed under simultaneous fundus imaging, its correlation with the established expanded nystagmus acuity function (NAFX), and its test–retest variability. RESULTS. The nystagmus optimal fixation function (NOFF) was defined as the logit transform of the fraction of data points meeting position and velocity criteria within a moving win- dow. A decreasing exponential relationship was found be- tween visual acuity deficit and the NOFF, yielding a 0.75 logMAR deficit for the poorest NOFF and diminishing deficits with improving foveation. As much as 96% of the points iden- tified as foveation events fell within 0.25° of the actual target. Good correlation (r ⫽ 0.96) was found between NOFF and NAFX. Test–retest variability was 0.49 logit units. CONCLUSIONS. The NOFF is a feasible method to quantify noisy nystagmus eye movement data. Its validation makes it a prom- ising outcome measure for the progression and treatment of nystagmus during early childhood. |
Muriel T. N. Panouillères; Christian Urquizar; Roméo Salemme; Denis Pélisson In: PLoS ONE, vol. 6, no. 2, pp. e17329, 2011. @article{Panouilleres2011, When goal-directed movements are inaccurate, two responses are generated by the brain: a fast motor correction toward the target and an adaptive motor recalibration developing progressively across subsequent trials. For the saccadic system, there is a clear dissociation between the fast motor correction (corrective saccade production) and the adaptive motor recalibration (primary saccade modification). Error signals used to trigger corrective saccades and to induce adaptation are based on post-saccadic visual feedback. The goal of this study was to determine if similar or different error signals are involved in saccadic adaptation and in corrective saccade generation. Saccadic accuracy was experimentally altered by systematically displacing the visual target during motor execution. Post-saccadic error signals were studied by manipulating visual information in two ways. First, the duration of the displaced target after primary saccade termination was set at 15, 50, 100 or 800 ms in different adaptation sessions. Second, in some sessions, the displaced target was followed by a visual mask that interfered with visual processing. Because they rely on different mechanisms, the adaptation of reactive saccades and the adaptation of voluntary saccades were both evaluated. We found that saccadic adaptation and corrective saccade production were both affected by the manipulations of post-saccadic visual information, but in different ways. This first finding suggests that different types of error signal processing are involved in the induction of these two motor corrections. Interestingly, voluntary saccades required a longer duration of post-saccadic target presentation to reach the same amount of adaptation as reactive saccades. Finally, the visual mask interfered with the production of corrective saccades only during the voluntary saccades adaptation task. These last observations suggest that post-saccadic perception depends on the previously performed action and that the differences between saccade categories of motor correction and adaptation occur at an early level of visual processing. |