EyeLink 临床和动眼神经眼球追踪出版物
EyeLink临床和oculomotor研究出版物至2023年(一些早于2024年)列在以下年份。您可以使用Saccadic Adaptation、Schizophrenia、Nystagmus等关键词搜索出版物。您还可以按年份搜索个人作者姓名和有限搜索(选择年份,然后单击搜索按钮)。如果我们错过了任何EyeLink临床或oculomotor文章,请给我们发电子邮件!
2010 |
Holly Bridge; Stephen L. Hicks; Jingyi Xie; Thomas W. Okell; Sabira K. Mannan; Iona Alexander; Alan Cowey; Christopher Kennard Visual activation of extra-striate cortex in the absence of V1 activation Journal Article In: Neuropsychologia, vol. 48, no. 14, pp. 4148–4154, 2010. @article{Bridge2010, When the primary visual cortex (V1) is damaged, there are a number of alternative pathways that can carry visual information from the eyes to extrastriate visual areas. Damage to the visual cortex from trauma or infarct is often unilateral, extensive and includes gray matter and white matter tracts, which can disrupt other routes to residual visual function. We report an unusual young patient, SBR, who has bilateral damage to the gray matter of V1, sparing the adjacent white matter and surrounding visual areas. Using functional magnetic resonance imaging (fMRI), we show that area MT+/V5 is activated bilaterally to visual stimulation, while no significant activity could be measured in V1. Additionally, the white matter tracts between the lateral geniculate nucleus (LGN) and V1 appear to show some degeneration, while the tracts between LGN and MT+/V5 do not differ from controls. Furthermore, the bilateral nature of the damage suggests that residual visual capacity does not result from strengthened interhemispheric connections. The very specific lesion in SBR suggests that the ipsilateral connection between LGN and MT+/V5 may be important for residual visual function in the presence of damage to V1. |
Norbert Bruggemann; Christine Klein; Christoph Helmchen Eye movement disorders in ATP13A2 dutation carriers (PARK9) Journal Article In: Movement Disorders, vol. 25, no. 15, pp. 2686–2687, 2010. @article{Bruggemann2010, Homozygous and compound-heterozygous* mutations in the ATP13A2 gene (PARK9 locus on chromosome 1p36) cause a rare, atypical form of autosomal recessive, early- onset parkinsonism, known as Kufor Rakeb disease (KRD).1 KRD patients present with additional pyramidal signs, dementia, and supra-nuclear gaze palsy.2,3 Asymptomatic carriers of ATP13A2 mutations have been reported to show subtle parkinsonian signs and abnormalities in functional and structural neuroimaging4; however, the impact of a single ATP13A2 mutation remains a matter of debate. |
Linda E. Campbell; Kathryn L. McCabe; Kate Leadbeater; Ulrich Schall; Carmel M. Loughland; Dominique Rich Visual scanning of faces in 22q11.2 deletion syndrome: Attention to the mouth or the eyes? Journal Article In: Psychiatry Research, vol. 177, no. 1-2, pp. 211–215, 2010. @article{Campbell2010, Previous research demonstrates that people with 22q11.2 deletion syndrome (22q11DS) have social and interpersonal skill deficits. However, the basis of this deficit is unknown. This study examined, for the first time, how people with 22q11DS process emotional face stimuli using visual scanpath technology. The visual scanpaths of 17 adolescents and age/gender matched healthy controls were recorded while they viewed face images depicting one of seven basic emotions (happy, sad, surprised, angry, fear, disgust and neutral). Recognition accuracy was measured concurrently. People with 22q11DS differed significantly from controls, displaying visual scanpath patterns that were characterised by fewer fixations and a shorter scanpath length. The 22q11DS group also spent significantly more time gazing at the mouth region and significantly less time looking at eye regions of the faces. Recognition accuracy was correspondingly impaired, with 22q11DS subjects displaying particular deficits for fear and disgust. These findings suggest that 22q11DS is associated with a maladaptive visual information processing strategy that may underlie affect recognition accuracy and social functioning deficits in this group. |
Chia-Chien Wu; Oh-Sang Kwon; Eileen Kowler Fitts's Law and speed/accuracy trade-offs during sequences of saccades: Implications for strategies of saccadic planning Journal Article In: Vision Research, vol. 50, no. 21, pp. 2142–2157, 2010. @article{Wu2010, Strategies of saccadic planning must take into account both the required level of accuracy of the saccades, and the time and resources needed to plan and execute the movements. To determine relationships between accuracy and time, we studied sequences of saccades made to scan a set of stationary targets located at the corners of an imaginary square. Target separation and size varied. The time taken to complete saccadic sequences increased with the required level of precision, in agreement with the classical Fitts's Law (1954) relationship. This was mainly due to the use of error-correcting secondary saccades, whose frequency increased with target separation and decreased with target size. Increases in the time spent fixating near each target did not increase the accuracy of the next primary saccade in the sequence. Instead, secondary saccades were the principal means of correcting landing errors of primary saccades. The results are consistent with a scanning strategy that discourages careful planning of individual saccades in favor of increasing the rate of saccadic production (i.e., exploration), using secondary saccades as needed to correct saccadic landing errors. |
Qing Yang; Marine Vernet; Christophe Orssaud; Pierre Bonfils; Alain Londero; Zoï Kapoula Central crosstalk for somatic tinnitus: Abnormal vergence eye movements Journal Article In: PLoS ONE, vol. 5, no. 7, pp. e11845, 2010. @article{Yang2010, Background: Frequent oulomotricity problems with orthoptic testing were reported in patients with tinnitus. This study examines with objective recordings vergence eye movements in patients with somatic tinnitus patients with ability to modify their subjective tinnitus percept by various movements, such as jaw, neck, eye movements or skin pressure. Methods: Vergence eye movements were recorded with the Eyelink II video system in 15 (23–63 years) control adults and 19 (36–62 years) subjects with somatic tinnitus. Findings: 1) Accuracy of divergence but not of convergence was lower in subjects with somatic tinnitus than in control subjects. 2) Vergence duration was longer and peak velocity was lower in subjects with somatic tinnitus than in control subjects. 3) The number of embedded saccades and the amplitude of saccades coinciding with the peak velocity of vergence were higher for tinnitus subjects. Yet, saccades did not increase peak velocity of vergence for tinnitus subjects, but they did so for controls. 4) In contrast, there was no significant difference of vergence latency between these two groups. Interpretation: The results suggest dysfunction of vergence areas involving cortical-brainstem-cerebellar circuits. We hypothesize that central auditory dysfunction related to tinnitus percept could trigger mild cerebellar-brainstem dysfunction or that tinnitus and vergence dysfunction could both be manifestations of mild cortical-brainstem-cerebellar syndrome reflecting abnormal cross-modality interactions between vergence eye movements and auditory signals. |
Eckart Zimmermann; Markus Lappe Motor signals in visual localization Journal Article In: Journal of Vision, vol. 10, no. 6, pp. 1–11, 2010. @article{Zimmermann2010, We demonstrate a strong sensory-motor coupling in visual localization in which experimental modification of the control of saccadic eye movements leads to an associated change in the perceived location of objects. Amplitudes of saccades to peripheral targets were altered by saccadic adaptation, induced by an artificial step of the saccade target during the eye movement, which leads the oculomotor system to recalibrate saccade parameters. Increasing saccade amplitudes induced concurrent shifts in perceived location of visual objects. The magnitude of perceptual shift depended on the size and persistence of errors between intended and actual saccade amplitudes. This tight agreement between the change of eye movement control and the change of localization shows that perceptual space is shaped by motor knowledge rather than simply constructed from visual input. |
Albert Moukheiber; Gilles Rautureau; Fernando Perez-Diaz; Robert Soussignan; Stéphanie Dubal; Roland Jouvent; Antoine Pelissolo Gaze avoidance in social phobia: Objective measure and correlates Journal Article In: Behaviour Research and Therapy, vol. 48, pp. 147–151, 2010. @article{Moukheiber2010, Gaze aversion could be a central component of the physiopathology of social phobia. The emotions of the people interacting with a person with social phobia seem to model this gaze aversion. Our research consists of testing gaze aversion in subjects with social phobia compared to control subjects in different emotional faces of men and women using an eye tracker. Twenty-six subjects with DSM-IV social phobia were recruited. Twenty-four healthy subjects aged and sex-matched constituted the control group. We looked at the number of fixations and the dwell time in the eyes area on the pictures. The main findings of this research are: confirming a significantly lower amount of fixations and dwell time in patients with social phobia as a general mean and for the 6 basic emotions independently from gender; observing a significant correlation between the severity of the phobia and the degree of gaze avoidance. However, no difference in gaze avoidance according to subject/picture gender matching was observed. These findings confirm and extend some previous results, and suggest that eye avoidance is a robust marker of persons with social phobia, which could be used as a behavioral phenotype for brain imagery studies on this disorder. |
Stefan Van der Stigchel The search for oculomotor inhibition interactions with working memory Journal Article In: Experimental Psychology, vol. 57, no. 6, pp. 429–435, 2010. @article{VanderStigchel2010c, When a saccadic target is presented simultaneously with a distractor, the distractor has to be inhibited in order to successfully perform an eye movement to the target. Insufficient inhibition results in an erroneous eye movement to the distractor. This study investigated whether the influence of a distractor on eye movements is mediated by working memory. A working memory task was added to a saccadic paradigm in which an irrelevant element had to be inhibited. Results show that participants made more erroneous saccades to the distractor when working memory was occupied. This suggests that working memory is involved in the oculomotor inhibition of saccadic distractors. |
Stefan Van der Stigchel; Tanja C. W. Nijboer The imbalance of oculomotor capture in unilateral visual neglect Journal Article In: Consciousness and Cognition, vol. 19, no. 1, pp. 186–197, 2010. @article{VanderStigchel2010b, Visual neglect has been associated with an imbalance in the level of activity in the saccadic system: activity in the contralesional field is suppressed, which makes target selection unlikely. We recorded eye movements of a patient with hemispatial neglect and a group of healthy participants during an oculomotor distractor paradigm. Results showed that the interfering effects of a distractor were very strong when presented in her ipsilesional visual field. However, when the distractor was presented in her contralesional field, there were no interfering effects when the target was presented in her ipsilesional field. These findings could not be explained by the presence of a visual field defect as revealed by the results of two hemianopic patients. Our results are in line with an imbalance in the level of activity in the saccadic system in visual neglect because visual elements presented in the contralesional field did not compete for saccadic selection. |
Stefan Van der Stigchel; Tanja C. W. Nijboer; D. P. Bergsma; Mathias Abegg; Jason J. S. Barton Anomalous global effects induced by 'blind' distractors in visual hemifield defects Journal Article In: Brain and Cognition, vol. 74, no. 1, pp. 66–73, 2010. @article{VanderStigchel2010a, Previous research has revealed that a stimulus presented in the blind visual field of participants with visual hemifield defects can evoke oculomotor competition, in the absence of awareness. Here we studied three cases to determine whether a distractor in a blind hemifield would be capable of inducing a global effect, a shift of saccade endpoint when target and distractor are close to each other, in participants with lesions of the optic radiations or striate cortex. We found that blind field distractors significantly shifted saccadic endpoints in two of three participants with lesions of either the striate cortex or distal optic radiations. The direction of the effect was paradoxical, however, in that saccadic endpoints shifted away from blind field distractors, whereas endpoints shifted towards distractors in the visible hemifields, which is the normal global effect. These results provide further evidence that elements presented in the blind visual field can generate modulatory interactions in the oculomotor system, which may differ from interactions in normal vision. |
Wieske Zoest; Mieke Donk Awareness of the saccade goal in oculomotor selection: Your eyes go before you know Journal Article In: Consciousness and Cognition, vol. 19, no. 4, pp. 861–871, 2010. @article{Zoest2010, The aim of the present study was to investigate how saccadic selection relates to people's awareness of the saliency and identity of a saccade goal. Observers were instructed to make an eye movement to either the most salient line segment (Experiment 1) or the only right-tilted element (Experiment 2) in a visual search display. The display was masked contingent on the first eye movement and after each trial observers indicated whether or not they had correctly selected the target. Whereas people's awareness concerning the saliency of the saccade goal was generally low, their awareness concerning the identity was high. Observers' awareness of the saccade goal was not related to saccadic performance. Whereas saccadic selection consistently varied as a function of saccade latency, people's awareness concerning the saliency or identity of the saccade goal did not. The results suggest that saccadic selection is primarily driven by subconscious processes. |
D. A. Wismeijer; Casper J. Erkelens; Raymond Van Ee; Mark Wexler Depth cue combination in spontaneous eye movements Journal Article In: Journal of Vision, vol. 10, no. 6, pp. 1–15, 2010. @article{Wismeijer2010, Where we look when we scan visual scenes is an old question that continues to inspire both fundamental and applied research. Recently, it has been reported that depth is an important variable in driving eye movements: the directions of spontaneous saccades tend to follow depth gradients, or, equivalently, surface tilts (L. Jansen, S. Onat, & P. König, 2009; M. Wexler & N. Ouarti, 2008). This has been found to hold for both simple and complex scenes and for a variety of depth cues. However, it is not known whether saccades are aligned with individual depth cues, or with a combination of depth cues. If saccades do follow a combination of depth cues, then it is interesting to ask whether this combination follows the same rules as the well-studied case of depth cue combination in conscious perception. We showed subjects surfaces inclined in depth, in which perspective and binocular disparity cues specified different plane orientations, with different degrees of both small and large conflict between the two sets of cues. We recorded subjects' spontaneous saccades while they scanned the scene, as well as their reports of perceived plane orientation. We found that distributions of spontaneous saccade directions followed the same pattern of depth cue combination as perceived surface orientation: a weighted linear combination of cues for small conflicts, and cue dominance for large conflicts. The weights assigned to the cues varied considerably from one subject to the next but were strongly correlated for saccades and perception; moreover, for both perception and saccades, cue weights could be modified by manipulating cue reliability in a way compatible with Bayesian theories of optimal cue combination. We also measured vergence, which allowed us to calculate the orientation of the plane fitted to points scanned in depth. Contrary to perception and saccades, vergence was dominated by a single cue, binocular disparity. |
2009 |
Alice G. Cruickshank; Eugene McSorley Involuntary inhibition of movement initiation alters oculomotor competition resolution Journal Article In: Experimental Brain Research, vol. 193, no. 3, pp. 467–476, 2009. @article{Cruickshank2009, Identifying a stimulus as the target for a goal-directed movement involves inhibiting competing responses. Separable inhibitory interconnections bias local competition to ensure only one stimulus is selected and to alter movement initiation. Behavioural evidence of these inhibitory processes comes from the effects of distracters on oculomotor landing positions and saccade latencies. Here, we investigate the relationship between these two sources of inhibition. Targets were presented with or without close and remote distracters. In separate experiments the possible position and identity of the target and distracters were manipulated. In all cases saccade landing position was found to be less affected by the presence of the close distracter when remote distracters were also present. The involuntary increase in the latency of saccade initiation caused by the presence of the remote distracters alters the state of competitive processes involved in selecting the saccade target thus changing its landing position. |
Thérèse Collins; Martin Rolfs; Heiner Deubel; Patrick Cavanagh Post-saccadic location judgments reveal remapping of saccade targets to non-foveal locations Journal Article In: Journal of Vision, vol. 9, no. 5, pp. 1–9, 2009. @article{Collins2009, The present study addresses the question of how objects are localized across saccades. In a task requiring participants to compare the location of a post-saccadic probe with the pre-saccadic target, we investigated the roles of saccade landing site and post-saccadic probe location. Saccade landing sites vary from trial to trial because of oculomotor error but can also be shifted by saccadic adaptation. Visual targets were extinguished during the saccade and reappeared after a short blank to counteract saccadic suppression of displacement. Performance in localizing targets after unadapted saccades was nearly veridical and independent of actual landing site, showing that trial-to-trial oculomotor error did not contribute to post-saccadic localization. This result suggests that much of the oculomotor error of saccades is included in the efference copy vector and this allows the recovery of a remapped target location that is often not foveal, but stable and accurate across trials. Displacement judgments relative to this remapped location will be independent of trial-to-trial variability in landing site. After adapted saccades, post-saccadic localization shifted in the direction opposite to adaptation but again, trial-by-trial landing site variability did not correlate with performance. This result suggests that the efference copy matches the planned upcoming saccade, be it adapted or not. |
Julien Cotti; Muriel T. N. Panouillères; Douglas P. Munoz; Jean-Louis Vercher; Denis Pélisson; Alain Guillaume Adaptation of reactive and voluntary saccades: different patterns of adaptation revealed in the antisaccade task Journal Article In: Journal of Physiology, vol. 587, no. 1, pp. 127–138, 2009. @article{Cotti2009, Sensorimotor adaptation restores and maintains the accuracy of goal-directed movements. It remains unclear whether these adaptive mechanisms modify actions by controlling peripheral premotor stages that send commands to the effectors and/or earlier processing stages involved in registration of target location. Here, we studied the effect of adaptation of saccadic eye movements, a well-established model of sensorimotor adaptation, in an antisaccade task. This task introduces a clear spatial dissociation between the actual target direction and the requested saccade direction because the correct movement direction is in the opposite direction from the target location. We used this requirement of a vector inversion to assess the level(s) of saccadic adaptation for two different types of adapted saccades. In two different experiments, we tested the transfer to antisaccades of the adaptation in one direction of reactive saccades to jumping targets and of scanning voluntary saccades within a target array. In the first experiment, we found that adaptation of reactive saccades transferred only to antisaccades in the adapted direction. In contrast, in the second experiment, adaptation of scanning voluntary saccades transferred to antisaccades in both the adapted and non-adapted directions. We conclude that adaptation of reactive saccades acts only downstream of the vector inversion required in the antisaccade task, whereas adaptation of voluntary saccades has a distributed influence, acting both upstream and downstream of vector inversion. |
Jay A. Edelman; Kitty Z. Xu Inhibition of voluntary saccadic eye movement commands by abrupt visual onsets Journal Article In: Journal of Neurophysiology, vol. 101, no. 3, pp. 1222–1234, 2009. @article{Edelman2009, Saccadic eye movements are made both to explore the visual world and to react to sudden sensory events. We studied the ability for humans to execute a voluntary (i.e., nonstimulus-driven) saccade command in the face of a suddenly appearing visual stimulus. Subjects were required to make a saccade to a memorized location when a central fixation point disappeared. At varying times relative to fixation point disappearance a visual distractor appeared at a random location. When the distractor appeared at locations distant from the target virtually no saccades were initiated in a 30- to 40-ms interval beginning 70-80 ms after appearance of the distractor. If the distractor was presented slightly earlier relative to saccade initiation then saccades tended to have smaller amplitudes, with velocity profiles suggesting that the distractor terminated them prematurely. In contrast, distractors appearing close to the saccade target elicited express saccade-like movements 70-100 ms after their appearance, although the saccade endpoint was generally scarcely affected by the distractor. An additional experiment showed that these effects were weaker when the saccade was made to a visible target in a delayed task and still weaker when the saccade itself was made in response to the abrupt appearance of a visual stimulus. A final experiment revealed that the effect is smaller, but quite evident, for very small stimuli. These results suggest that the transient component of a visual response can briefly but almost completely suppress a voluntary saccade command, but only when the stimulus evoking that response is distant from the saccade goal. |
Tom C. A. Freeman; Rebecca A. Champion; Jane H. Sumnall; Robert J. Snowden Do we have direct access to retinal image motion during smooth pursuit eye movements? Journal Article In: Journal of Vision, vol. 9, no. 1, pp. 1–11, 2009. @article{Freeman2009, One way the visual system estimates object motion during pursuit is to combine estimates of eye velocity and retinal motion. This questions whether observers need direct access to retinal motion during pursuit. We tested this idea by varying the correlation between retinal motion and objective motion in a two-interval speed discrimination task. Responses were classified according to three motion cues: retinal speed (based on measured eye movements), objective speed, and the relative motion between pursuit target and stimulus. In the first experiment, feedback was based on relative motion and this cue fit the response curves best. In the second experiment, simultaneous relative motion was removed but observers still used the sequential relative motion between pursuit target and dot pattern to make their judgements. In a final experiment, feedback was given explicitly on the retinal motion, using online measurements of eye movements. Nevertheless, sequential relative motion still provided the best account of the data. The results suggest that observers do not have direct access to retinal motion when making perceptual judgements about movement during pursuit. |
Karsten Georg; Markus Lappe Effects of saccadic adaptation on visual localization before and during saccades Journal Article In: Experimental Brain Research, vol. 192, no. 1, pp. 9–23, 2009. @article{Georg2009, Short-term saccadic adaptation is a mechanism that adjusts saccade amplitude to accurately reach an intended saccade target. Short-term saccadic adaptation induces a shift of perceived localization of objects flashed before the saccade. This shift, being detectable only before an adapted saccade, disappears at some time around saccade onset. Up to now, the exact time course of this effect has remained unknown. In previous experiments, the mislocalization caused by this adaptation-induced shift was overlapping with the mislocalization caused by a different, saccade-related localization error, the peri-saccadic compression. Due to peri-saccadic compression, objects flashed immediately at saccade onset appear compressed towards the saccade target. First, we tested whether the adaptation-induced shift and the peri-saccadic compression were either independent or related processes. We performed experiments with two different luminance-contrast conditions to separate the adaptation-induced shift and the peri-saccadic compression. Human participants had to indicate the perceived location of briefly presented stimuli before, during or after an adapted saccade. Adaptation-induced shift occurred similarly in either contrast condition, with or without peri-saccadic compression. Second, after validating the premise of both processes being independent and superimposing, we aimed at characterizing the time course of the adaptation-induced shift in more detail. Being present up to 1 s before an adapted saccade, the adaptation-induced shift begins to gradually decline from about 150 ms before saccade onset, and ceases during the saccade. A final experiment revealed that visual references make a major contribution to adaptation-induced mislocalization. |
Anna Montagnini; Leonardo Chelazzi In: Vision Research, vol. 49, no. 10, pp. 1316–1328, 2009. @article{Montagnini2009, We investigated human oculomotor behaviour in a Go-NoGo saccadic task in which the saccadic response to a peripheral visual target was to be inhibited in a minority of trials (NoGo trials). Different from classical experimental paradigms on the inhibitory control of intended actions, in our task the inhibitory cue was identical to the saccadic target (used in Go trials) in timing, location and shape-the only difference being its colour. By analysing the latency and the metrics of saccades erroneously executed after a NoGo instruction (NoGo-escapes), we observed a characteristic pattern of performance: first, we observed a decrease in the amplitude of NoGo-escapes with increasing latency; second, we revealed a consistent population of long-latency small saccades opposite in direction to the NoGo cue; finally, we found a strong side-specific inhibitory effect in terms of saccadic reaction times, on trials immediately following a NoGo trial. In addition, we manipulated the readiness to initiate a saccade towards the visual target, by introducing a probability bias in the random sequence of target locations. We found that the capacity to inhibit the impending saccade was improved for the most likely target location, i.e. the condition corresponding to the increased readiness for movement execution. Overall, our results challenge the notion of a central inhibitory mechanism independent from movement preparation. More precisely, they indicate that the two mechanisms (action preparation and action inhibition) interact dynamically, possibly sharing spatially-specific mechanisms, and are similarly affected by particular contextual manipulations. |
Camille Morvan; Mark Wexler The nonlinear structure of motion perception during smooth eye movements Journal Article In: Journal of Vision, vol. 9, no. 7, pp. 1–13, 2009. @article{Morvan2009, To perceive object motion when the eyes themselves undergo smooth movement, we can either perceive motion directly-by extracting motion relative to a background presumed to be fixed-or through compensation, by correcting retinal motion by information about eye movement. To isolate compensation, we created stimuli in which, while the eye undergoes smooth movement due to inertia, only one object is visible-and the motion of this stimulus is decoupled from that of the eye. Using a wide variety of stimulus speeds and directions, we rule out a linear model of compensation, in which stimulus velocity is estimated as a linear combination of retinal and eye velocities multiplied by a constant gain. In fact, we find that when the stimulus moves in the same direction as the eyes, there is little compensation, but when movement is in the opposite direction, compensation grows in a nonlinear way with speed. We conclude that eye movement is estimated from a combination of extraretinal and retinal signals, the latter based on an assumption of stimulus stationarity. Two simple models, in which the direction of eye movement is computed from the extraretinal signal and the speed from the retinal signal, account well for our results. |
Mulckhuyse Mulckhuyse; Stefan Van der Stigchel; Jan Theeuwes Early and late modulation of saccade deviations by target distractor similarity Journal Article In: Journal of Neurophysiology, vol. 102, no. 3, pp. 1451–1458, 2009. @article{Mulckhuyse2009, In this study, we investigated the time course of oculomotor competition between bottom-up and top-down selection processes using saccade trajectory deviations as a dependent measure. We used a paradigm in which we manipulated saccade latency by offsetting the fixation point at different time points relative to target onset. In experiment 1, observers made a saccade to a filled colored circle while another irrelevant distractor circle was presented. The distractor was either similar (i.e., identical) or dissimilar to the target. Results showed that the strength of saccade deviation was modulated by target distractor similarity for short saccade latencies. To rule out the possibility that the similar distractor affected the saccade trajectory merely because it was identical to the target, the distractor in experiment 2 was a square shape of which only the color was similar or dissimilar to the target. The results showed that deviations for both short and long latencies were modulated by target distractor similarity. When saccade latencies were short, we found less saccade deviation away from a similar than from a dissimilar distractor. When saccade latencies were long, the opposite pattern was found: more saccade deviation away from a similar than from a dissimilar distractor. In contrast to previous findings, our study shows that task-relevant information can already influence the early processes of oculomotor control. We conclude that competition between saccadic goals is subject to two different processes with different time courses: one fast activating process signaling the saliency and task relevance of a location and one slower inhibitory process suppressing that location. |
Jérôme Munuera; Pierre Morel; Jean-Rene Duhamel; Sophie Deneve Optimal sensorimotor control in eye movement sequences Journal Article In: Journal of Neuroscience, vol. 29, no. 10, pp. 3026–3035, 2009. @article{Munuera2009, Fast and accurate motor behavior requires combining noisy and delayed sensory information with knowledge of self-generated body motion; much evidence indicates that humans do this in a near-optimal manner during arm movements. However, it is unclear whether this principle applies to eye movements. We measured the relative contributions of visual sensory feedback and the motor efference copy (and/or proprioceptive feedback) when humans perform two saccades in rapid succession, the first saccade to a visual target and the second to a memorized target. Unbeknownst to the subject, we introduced an artificial motor error by randomly "jumping" the visual target during the first saccade. The correction of the memory-guided saccade allowed us to measure the relative contributions of visual feedback and efferent copy (and/or proprioceptive feedback) to motor-plan updating. In a control experiment, we extinguished the target during the saccade rather than changing its location to measure the relative contribution of motor noise and target localization error to saccade variability without any visual feedback. The motor noise contribution increased with saccade amplitude, but remained <30% of the total variability. Subjects adjusted the gain of their visual feedback for different saccade amplitudes as a function of its reliability. Even during trials where subjects performed a corrective saccade to compensate for the target-jump, the correction by the visual feedback, while stronger, remained far below 100%. In all conditions, an optimal controller predicted the visual feedback gain well, suggesting that humans combine optimally their efferent copy and sensory feedback when performing eye movements. |
Lauri Nummenmaa; Jukka Hyönä; Manuel G. Calvo Emotional scene content drives the saccade generation system reflexively Journal Article In: Journal of Experimental Psychology: Human Perception and Performance, vol. 35, no. 2, pp. 305–323, 2009. @article{Nummenmaa2009, The authors assessed whether parafoveal perception of emotional content influences saccade programming. In Experiment 1, paired emotional and neutral scenes were presented to parafoveal vision. Participants performed voluntary saccades toward either of the scenes according to an imperative signal (color cue). Saccadic reaction times were faster when the cue pointed toward the emotional picture rather than toward the neutral picture. Experiment 2 replicated these findings with a reflexive saccade task, in which abrupt luminosity changes were used as exogenous saccade cues. In Experiment 3, participants performed vertical reflexive saccades that were orthogonal to the emotional-neutral picture locations. Saccade endpoints and trajectories deviated away from the visual field in which the emotional scenes were presented. Experiment 4 showed that computationally modeled visual saliency does not vary as a function of scene content and that inversion abolishes the rapid orienting toward the emotional scenes. Visual confounds cannot thus explain the results. The authors conclude that early saccade target selection and execution processes are automatically influenced by emotional picture content. This reveals processing of meaningful scene content prior to overt attention to the stimulus. |
Antje Nuthmann; Reinhold Kliegl An examination of binocular reading fixations based on sentence corpus data Journal Article In: Journal of Vision, vol. 9, no. 5, pp. 31–31, 2009. @article{Nuthmann2009a, Binocular eye movements of normal adult readers were examined as they read single sentences. Analyses of horizontal and vertical fixation disparities indicated that the most prevalent type of disparate fixation is crossed (i.e., the left eye is located further to the right than the right eye) while the left eye frequently fixates somewhat above the right eye. The Gaussian distribution of the binocular fixation point peaked 2.6 cm in front of the plane of text, reflecting the prevalence of horizontally crossed fixations. Fixation disparity accumulates during the course of successive saccades and fixations within a line of text, but only to an extent that does not compromise single binocular vision. In reading, the version and vergence system interact in a way that is qualitatively similar to what has been observed in simple nonreading tasks. Finally, results presented here render it unlikely that vergence movements in reading aim at realigning the eyes at a given saccade target word. |
Andre Kaminiarz; K. Konigs; Frank Bremmer Task influences on the dynamic properties of fast eye movements Journal Article In: Journal of Vision, vol. 9, no. 13, pp. 1–11, 2009. @article{Kaminiarz2009a, It is widely debated whether fast phases of the reflexive optokinetic nystagmus (OKN) share properties with another class of fast eye movements, visually guided saccades. Conclusions drawn from previous studies were complicated by the fact that a subject's task influences the exact type of OKN: stare vs. look nystagmus. With our current study we set out to determine in the same subjects the exact dynamic properties (main sequence) of various forms of fast eye movements. We recorded fast phases of look and stare nystagmus as well as visually guided saccades. Our data clearly show that fast phases of look and stare nystagmus differ with respect to their main sequence. Fast phases of stare nystagmus were characterized by their lower peak velocities and longer durations as compared to fast phases of look nystagmus. Furthermore we found no differences between fast phases of stare nystagmus evoked with limited and unlimited dot lifetimes. Visually guided saccades were on the same main sequence as fast phases of look nystagmus, while they had higher peak velocities and shorter durations than fast phases of stare nystagmus. Our data underline the critical role of behavioral tasks (e.g., reflexive vs. intentional) for the exact spatiotemporal characteristics of fast eye movements. |
Andre Kaminiarz; K. Konigs; Frank Bremmer The main sequence of human optokinetic afternystagmus (OKAN) Journal Article In: Journal of Neurophysiology, vol. 101, no. 6, pp. 2889–2897, 2009. @article{Kaminiarz2009, Different types of fast eye movements, including saccades and fast phases of optokinetic nystagmus (OKN) and optokinetic afternystagmus (OKAN), are coded by only partially overlapping neural networks. This is a likely cause for the differences that have been reported for the dynamic parameters of fast eye movements. The dependence of two of these parameters-peak velocity and duration-on saccadic amplitude has been termed "main sequence." The main sequence of OKAN fast phases has not yet been analyzed. These eye movements are unique in that they are generated by purely subcortical control mechanisms and that they occur in complete darkness. In this study, we recorded fast phases of OKAN and OKN as well as visually guided and spontaneous saccades under identical background conditions because background characteristics have been reported to influence the main sequence of saccades. Our data clearly show that fast phases of OKAN and OKN differ with respect to their main sequence. OKAN fast phases were characterized by their lower peak velocities and longer durations compared with those of OKN fast phases. Furthermore we found that the main sequence of spontaneous saccades depends heavily on background characteristics, with saccades in darkness being slower and lasting longer. On the contrary, the main sequence of visually guided saccades depended on background characteristics only very slightly. This implies that the existence of a visual saccade target largely cancels out the effect of background luminance. Our data underline the critical role of environmental conditions (light vs. darkness), behavioral tasks (e.g., spontaneous vs. visually guided), and the underlying neural networks for the exact spatiotemporal characteristics of fast eye movements. |
Dirk Kerzel; Sabine Born; David Souto Smooth pursuit eye movements and perception share target selection, but only some central resources Journal Article In: Behavioural Brain Research, vol. 201, no. 1, pp. 66–73, 2009. @article{Kerzel2009, Smooth pursuit eye movements have been linked to perception by a common attentional mechanism. We investigated whether perceptual performance was traded for smooth pursuit performance. While tracking a red target cross, observers had to discriminate the orientation of a flashed peripheral grating. We manipulated the priority given to the two tasks. Pursuit gain changed according to observers' effort to pursue the target, but perceptual discrimination of the peripheral flash was not affected by these changes, suggesting that smooth pursuit does not use the same resources as perception. Complete resource sharing may be confined to situations involving multiple moving objects. Next, we added a second perceptual task on the foveal pursuit target. Foveal discrimination performance was traded for peripheral discrimination performance and pursuit gain followed the perceptual priorities. Thus, smooth pursuit gain is affected by which target has been selected for enhanced perceptual processing, but that does not imply shared perceptual resources. |
Reinhold Kliegl; Martin Rolfs; Jochen Laubrock; Ralf Engbert Microsaccadic modulation of response times in spatial attention tasks Journal Article In: Psychological Research, vol. 73, no. 2, pp. 136–146, 2009. @article{Kliegl2009, Covert shifts of attention are usually reflected in RT differences between responses to valid and invalid cues in the Posner spatial attention task. Such inferences about covert shifts of attention do not control for microsaccades in the cue-target interval. We analyzed the effects of microsaccade orientation on RTs in four conditions, crossing peripheral visual and auditory cues with peripheral visual and auditory discrimination targets. Reaction time was generally faster on trials without microsaccades in the cue-target interval. If microsaccades occurred, the target-location congruency of the last microsaccade in the cue-target interval interacted in a complex way with cue validity. For valid visual cues, irrespective of whether the discrimination target was visual or auditory, target-congruent microsaccades delayed RT. For invalid cues, target-incongruent microsaccades facilitated RTs for visual target discrimination but delayed RT for auditory target discrimination. No reliable effects on RT were associated with auditory cues or with the first microsaccade in the cue-target interval. We discuss theoretical implications on the relation about spatial attention and oculomotor processes. © 2008 Springer-Verlag. |
Wilhelm Bernhard Kloke; Wolfgang Jaschinski; Stephanie Jainta Microsaccades under monocular viewing conditions Journal Article In: Journal of Eye Movement Research, vol. 3, no. 1, pp. 1–7, 2009. @article{Kloke2009, Among the eye movements during fixation, the function of small saccades occuring quite commonly at fixation is still unclear. It has been reported that a substantial number of these microsaccades seem to occur in only one of the eyes. The aim of the present study is to investigate microsaccades in monocular stimulation conditions. Although this is an artificial test condition which does not occur in natural vision, this monocular presentation paradigm allows for a critical test of a presumptive monoc- ular mechanism of saccade generation. Results in these conditions can be compared with the normal binocular stimulation mode. We checked the statistical properties of microsaccades under monocular stimulation conditions and found no indication for specific interactions for monocularly detected small saccades, which might be present if they were based on a monocular physiological activation mechanism. |
Christopher M. Knapp; Irene Gottlob; Rebecca J. McLean; Suzzane Rafelt; Frank A. Proudlock Effect of distance upon horizontal and vertical look and stare OKN Journal Article In: Journal of Vision, vol. 9, no. 12, pp. 1–9, 2009. @article{Knapp2009, Previous reports suggest that distance influences horizontal stare OKN gains; however, the effect of distance on vertical OKN and look OKN is unknown. Horizontal and vertical look and stare OKN gains were recorded in 16 healthy volunteers (velocity 38.4 degrees /s) at three distances (0.3 m, 1 m, and 2.5 m) and two different stimulus sizes. Asymmetry of responses and correlation of gains in different directions were compared. Measurements at near were compared with and without glasses. Distance did not significantly affect horizontal look and stare OKN or vertical look OKN, however, downward stare OKN gains were reduced at greater distances (p = 0.002). Mean downward stare OKN gains recorded in each individual were strongly correlated to leftward and rightward gains but not upward gains. In contrast, upward OKN gains were not correlated to gains in leftward, rightward, or downward directions. Downward stare OKN responses are significantly sensitive to the effects of distance, whereas stare OKN in other directions and look OKN responses in all directions are not. Individual mean downward stare OKN gains are more closely related to horizontal responses rather than upward responses. This suggests that the downward OKN system is more functionally related to the horizontal system rather than the upward OKN system. |
Todd M. Herrington; Nicolas Y. Masse; Karim J. Hachmeh; Jackson E. T. Smith; John A. Assad; Erik P. Cook In: Journal of Neuroscience, vol. 29, no. 18, pp. 5793–5805, 2009. @article{Herrington2009, It is widely reported that the activity of single neurons in visual cortex is correlated with the perceptual decision of the subject. The strength of this correlation has implications for the neuronal populations generating the percepts. Here we asked whether microsaccades, which are small, involuntary eye movements, contribute to the correlation between neural activity and behavior. We analyzed data from three different visual detection experiments, with neural recordings from the middle temporal (MT), lateral intraparietal (LIP), and ventral intraparietal (VIP) areas. All three experiments used random dot motion stimuli, with the animals required to detect a transient or sustained change in the speed or strength of motion. We found that microsaccades suppressed neural activity and inhibited detection of the motion stimulus, contributing to the correlation between neural activity and detection behavior. Microsaccades accounted for as much as 19% of the correlation for area MT, 21% for area LIP, and 17% for VIP. While microsaccades only explain part of the correlation between neural activity and behavior, their effect has implications when considering the neuronal populations underlying perceptual decisions. |
Timothy L. Hodgson; Benjamin A. Parris; Nicola J. Gregory; Tracey Jarvis The saccadic Stroop effect: Evidence for involuntary programming of eye movements by linguistic cues Journal Article In: Vision Research, vol. 49, no. 5, pp. 569–574, 2009. @article{Hodgson2009, The effect of automatic priming of behaviour by linguistic cues is well established. However, as yet these effects have not been directly demonstrated for eye movement responses. We investigated the effect of linguistic cues on eye movements using a modified version of the Stroop task in which a saccade was made to the location of a peripheral colour patch which matched the "ink" colour of a centrally presented word cue. The words were either colour words ("red", "green", "blue", "yellow") or location words ("up", "down", "left", "right"). As in the original version of the Stroop task the identity of the word could be either congruent or incongruent with the response location. The results showed that oculomotor programming was influenced by word identity, even though the written word provided no task relevant information. Saccade latency was increased on incongruent trials and an increased frequency of error saccades was observed in the direction congruent with the word identity. The results argue against traditional distinctions between reflexive and voluntary programming of saccades and suggest that linguistic cues can also influence eye movement programming in an automatic manner. |
Po-Jang Hsieh; Peter U. Tse Microsaccade rate varies with subjective visibility during motion-induced blindness Journal Article In: PLoS ONE, vol. 4, no. 4, pp. e5163, 2009. @article{Hsieh2009b, Motion-induced blindness (MIB) occurs when a dot embedded in a motion field subjectively vanishes. Here we report the first psychophysical data concerning effects of microsaccade/eyeblink rate upon perceptual switches during MIB. We find that the rate of microsaccades/eyeblink rises before and after perceptual transitions from not seeing to seeing the dot, and decreases before perceptual transitions from seeing it to not seeing it. In addition, event-related fMRI data reveal that, when a dot subjectively reappears during MIB, the blood oxygen-level dependent (BOLD) signal increases in V1v and V2v and decreases in contralateral hMT+. These BOLD signal changes observed upon perceptual state changes in MIB could be driven by the change of perceptual states and/or a confounding factor, such as the microsaccade/eyeblink rate. |
Lynn Huestegge; Iring Koch Dual-task crosstalk between saccades and manual responses Journal Article In: Journal of Experimental Psychology: Human Perception and Performance, vol. 35, no. 2, pp. 352–362, 2009. @article{Huestegge2009, Between-task crosstalk has been discussed as an important source for dual-task costs. In this study, the authors examine concurrently performed saccades and manual responses as a means of studying the role of response-code conflict between 2 tasks. In Experiment 1, participants responded to an imperative auditory stimulus with a left or a right key press (manual task), a left or a right saccade (saccade task), or both. In Experiments 2 and 3, participants crossed their hands, and a modest (Experiment 2) or substantial (Experiment 3) degree of between-task response-code conflict through specific instructions was introduced. In Experiment 4, response codes across tasks were compatible, and stimulus-response mappings in both tasks were incompatible. Overall, the results indicate that performance not only in manual responses but also in saccades suffers from dual-task conditions, even though saccades were typically performed first and are usually assumed to be controlled quite independently. Moreover, the systematic introduction of response-code conflict between tasks modulated the pattern of dual-task performance. The authors propose confusability of response codes as an underlying mechanism of the observed effects of between-task crosstalk. |
Stephanie Jainta; Jörg Hoormann; W. Jaschinski Accommodation modulates the individual difference between objective and subjective measures of the final convergence step response Journal Article In: Ophthalmic and Physiological Optics, vol. 29, no. 2, pp. 162–172, 2009. @article{Jainta2009, Measuring vergence eye movements with dichoptic nonius lines (subjectively) usually leads to an overestimation of the vergence state after a step response: a subjective vergence overestimation (SVO). We tried to reduce this SVO by presenting a vergence stimulus that decoupled vergence and accommodation during the step response, i.e. reduced the degree of 'forced vergence'. In a mirror-stereoscope, we estimated convergence step responses with nonius lines presented at 1000 ms after a disparity step-stimulus and compared it to objective recordings (EyeLink II; n = 6). We presented a vertical line, a cross/rectangle stimulus and a difference-of-gaussians (DOG) pattern. For 180 min arc step stimuli, the subjective measures revealed a larger final vergence response than the objective measure; for the vertical line this SVO was 20 min arc, while it was significantly smaller for the DOG (12 min arc). For 60 min arc step-responses, no overestimation was observed. Additionally, we measured accommodation, which changed more for the DOG-pattern compared with the line-stimulus; this relative increase correlated with the corresponding relative change of SVO (r = 0.77). Both findings (i.e. no overestimation for small steps and a weaker one for the DOG-pattern) reflect lesser conflicting demand on accommodation and vergence under 'forced-vergence' viewing; consequently, sensory compensation is reduced and subjective and objective measures of vergence step responses tend to agree. |
Casimir J. H. Ludwig; Simon Farrell; Lucy A. Ellis; Iain D. Gilchrist The mechanism underlying inhibition of saccadic return Journal Article In: Cognitive Psychology, vol. 59, no. 2, pp. 180–202, 2009. @article{Ludwig2009a, Human observers take longer to re-direct gaze to a previously fixated location. Although there has been some exploration of the characteristics of inhibition of saccadic return (ISR), the exact mechanisms by which ISR operates are currently unknown. In the framework of accumulation models of response times, in which evidence is integrated over time to a response threshold, ISR could reflect a reduction in the rate of accumulation for saccades to return locations or an increase in the effective criterion for response. In two experiments, participants generated sequences of three saccades, in response to a peripheral or a central cue. ISR occurred across these manipulations: saccade latency was consistently increased for movements to the immediately previously fixated location. Latency distributions from individual observers were fit with a Linear Ballistic Accumulator model. ISR was best accounted for as a change in the accumulation rate. We suggest this parameter represents the overall desirability of a particular course of action, the evidence for which may be derived from a variety of sensory and non-sensory sources. |
Ayelet McKyton; Yoni Pertzov; Ehud Zohary Pattern matching is assessed in retinotopic coordinates Journal Article In: Journal of Vision, vol. 9, no. 13, pp. 1–10, 2009. @article{McKyton2009, We typically examine scenes by performing multiple saccades to different objects of interest within the image. Therefore, an extra-retinotopic representation, invariant to the changes in the retinal image caused by eye movements, might be useful for high-level visual processing. We investigate here, using a matching task, whether the representation of complex natural images is retinotopic or screen-based. Subjects observed two simultaneously presented images, made a saccadic eye movement to a new fixation point, and viewed a third image. Their task was to judge whether the third image was identical to one of the two earlier images or different. Identical images could appear either in the same retinotopic position, in the same screen position, or in totally different locations. Performance was best when the identical images appeared in the same retinotopic position and worst when they appeared in the opposite hemifield. Counter to commonplace intuition, no advantage was conferred from presenting the identical images in the same screen position. This, together with performance sensitivity for image translation of a few degrees, suggests that image matching, which can often be judged without overall recognition of the scene, is mostly determined by neuronal activity in earlier brain areas containing a strictly retinotopic representation and small receptive fields. |
Eugene McSorley; Alice G. Cruickshank; Laura A. Inman The development of the spatial extent of oculomotor inhibition Journal Article In: Brain Research, vol. 1298, pp. 92–98, 2009. @article{McSorley2009b, Inhibition is intimately involved in the ability to select a target for a goal-directed movement. The effect of distracters on the deviation of oculomotor trajectories and landing positions provides evidence of such inhibition. Individual saccade trajectories and landing positions may deviate initially either towards, or away from, a competing distracter-the direction and extent of this deviation depends upon saccade latency and the target to distracter separation. However, the underlying commonality of the sources of oculomotor inhibition has not been investigated. Here we report the relationship between distracter-related deviation of saccade trajectory, landing position and saccade latency. Observers saccaded to a target which could be accompanied by a distracter shown at various distances from very close (10 angular degrees) to far away (120 angular degrees). A fixation-gap paradigm was used to manipulate latency independently of the influence of competing distracters. When distracters were close to the target, saccade trajectory and landing position deviated toward the distracter position, while at greater separations landing position was always accurate but trajectories deviated away from the distracters. Different spatial patterns of deviations across latency were found. This pattern of results is consistent with the metrics of the saccade reflecting coarse pooling of the ongoing activity at the distracter location: saccade trajectory reflects activity at saccade initiation while landing position reveals activity at saccade end. |
Eugene McSorley; Patrick Haggard; Robin Walker The spatial and temporal shape of oculomotor inhibition Journal Article In: Vision Research, vol. 49, no. 6, pp. 608–614, 2009. @article{McSorley2009, Selecting a stimulus as the target for a goal-directed movement involves inhibiting other competing possible responses. Inhibition has generally proved hard to study behaviorally, because it results in no measurable output. The effect of distractors on the shape of oculomotor and manual trajectories provide evidence of such inhibition. Individual saccades may deviate initially either towards, or away from, a competing distractor - the direction and extent of this deviation depends upon saccade latency, target predictability and the target to distractor separation. The experiment reported here used these effects to show how inhibition of distractor locations develops over time. Distractors could be presented at various distances from unpredictable and predictable targets in two separate experiments. The deviation of saccade trajectories was compared between trials with and without distractors. Inhibition was measured by saccade trajectory deviation. Inhibition was found to increase as the distractor distance from target decreased but was found to increase with saccade latency at all distractor distances (albeit to different peaks). Surprisingly, no differences were found between unpredictable and predictable targets perhaps because our saccade latencies were generally long (∼260-280 ms.). We conclude that oculomotor inhibition of saccades to possible target objects involves the same mechanisms for all distractor distances and target types. |
R. Bibi; Jay A. Edelman The influence of motor yraining onhuman express saccade production Journal Article In: Journal of Neurophysiology, vol. 102, no. 6, pp. 3101–3110, 2009. @article{Bibi2009, Express saccadic eye movements are saccades of extremely short latency. In monkey, express saccades have been shown to occur much more frequently when the monkey has been trained to make saccades in a particular direction to targets that appear in predictable locations. Such results suggest that express saccades occur in large number only under highly specific conditions, leading to the view that vector-specific training and motor preparatory processes are required to make an express saccade of a particular magnitude and direction. To evaluate this hypothesis in humans, we trained subjects to make saccades quickly to particular locations and then examined whether the frequency of express saccades depended on training and the number of possible target locations. Training significantly decreased saccade latency and increased express saccade production to both trained and untrained locations. Increasing the number of possible target locations (two vs. eight possible targets) led to only a modest increase of saccade latency. For most subjects, the probability of express saccade occurrence was much higher than that expected if vector-specific movement preparation were necessary for their production. These results suggest that vector-specific motor preparation and vector-specific saccade training are not necessary for express saccade production in humans and that increases in express saccade production are due in part to a facilitation in fixation disengagement or else a general enhancement in the ability of the saccadic system to respond to suddenly appearing visual stimuli. |
P. Cardoso-Leite; Andrei Gorea Comparison of perceptual and motor decisions via confidence judgments and saccade curvature Journal Article In: Journal of Neurophysiology, vol. 101, no. 6, pp. 2822–2836, 2009. @article{CardosoLeite2009, This study investigated the effects on perceptual and motor decisions of low-contrast distractors, presented 5 degrees on the left and/or the right of the fixation point. Perceptual decisions were assessed with a yes/no (distractor) detection task. Motor decisions were assessed via these distractors' effects on the trajectory of an impending saccade to a distinct imperative stimulus, presented 10 degrees above fixation 50 ms after the distractor(s). Saccade curvature models postulate that distractors activate loci on a motor map that evoke reflexive saccades and that the distractor evoked activity is inhibited to prevent reflexive orienting to the cost of causing a saccade curvature away from the distractor. Depending on whether or not each of these processes depends on perceptual detection, one can predict the relationships between saccades' curvature and perceptual responses (classified as correct rejections, misses, false alarms, and hits). The results show that saccades curve away from distractors only when observers report them to be present. Furthermore, saccade deviation is correlated (on a trial-by-trial basis) with the inferred internal response associated with the perceptual report: the stronger the distractor-evoked perceptual response, the more saccades deviate away from the distractor. Also in contrast with a supersensitive motor system, perceptual sensitivity is systematically higher than the motor sensitivity derived from the distributions of the saccades' curvatures. Finally, when both distractors are present (and straight saccades are expected), the sign of saccades' curvature is correlated with observers' perceptual bias/criterion. Overall the results point to a strong perceptual-motor association. |
Matteo Valsecchi; Massimo Turatto Microsaccadic responses in a bimodal oddball task Journal Article In: Psychological Research, vol. 73, no. 1, pp. 23–33, 2009. @article{Valsecchi2009, In a visual oddball task the presentation of rare targets induces a prolonged microsaccadic inhibition as compared to standards. Here, we replicated this effect also in the auditory modality. In addition, although auditory standards induced a more limited modulation of microsaccadic frequency as compared to visual standards, auditory oddballs induced a prolonged microsaccadic inhibition. With bimodal standard stimuli the microsaccadic response was determined by the attended modality, resembling that produced by attended unimodal stimuli. The present findings support the idea that the microsaccadic response to oddball and standard stimuli is partly driven by cognitive mechanisms common to both the visual and the auditory modality, and that microsaccades can be used as an implicit behavioral measure of ongoing cognitive processes. |
Stefan Van der Stigchel; Manon Mulckhuyse; Jan Theeuwes Eye cannot see it: The interference of subliminal distractors on saccade metrics Journal Article In: Vision Research, vol. 49, no. 16, pp. 2104–2109, 2009. @article{VanderStigchel2009, The present study investigated whether subliminal (unconsciously perceived) visual information influences eye movement metrics, like saccade trajectories and endpoints. Participants made eye movements upwards and downwards while a subliminal distractor was presented in the periphery. Results showed that the subliminal distractor interfered with the execution of an eye movement, although the effects were smaller compared to a control experiment in which the distractor was presented supraliminal. Because saccade metrics are mediated by low level brain areas, this indicates that subliminal visual information evokes competition at a very low level in the oculomotor system. |
Marine Vernet Binocular motor coordination during saccades and fixations while reading: A magnitude and time analysis Journal Article In: Journal of Vision, vol. 9, no. 2009, pp. 1–13, 2009. @article{Vernet2009, Reading involves saccades and fixations. Misalignment of the eyes should be small enough to allow sensory fusion. Recent studies reported disparity of the eyes during fixations. This study examines disconjugacy, i.e. change in disparity over time, both during saccades and fixations. Text reading saccades and saccades to single targets of similar sizes (2.5-) are compared. Young subjects were screened to avoid problems of binocular vision and oculomotor vergence. The results show high quality of motor binocular coordination in both tasks: the amplitude difference between the saccade of the eyes was approximately 0.16-; during the fixation period, the drift difference was only 0.13-. The disconjugate drift occurred mainly during the first 48 ms of fixation, was equally distributed to the eyes and was often reducing the saccade disconjugacy. Quality of coordination regardless of the task is indicative of robust physiological mechanisms. We suggest the existence of active binocular control mechanisms in which vergence signals may have a central role. Even computation of saccades may be based on continuous interaction between saccade and vergence. |
Marine Vernet; Qing Yang; Marie Gruselle; Mareike Trams; Zoï Kapoula Switching between gap and overlap pro-saccades: Cost or benefit? Journal Article In: Experimental Brain Research, vol. 197, no. 1, pp. 49–58, 2009. @article{Vernet2009a, Triggering of saccades depends on the task: in the gap task, fixation point switches off and target appears after a gap period; in the overlap task, target appears while fixation point is still on. Saccade latencies are shorter in the gap task, due to fixation disengagement and advanced movement preparation during the gap. The two modes of initiation are also hypothesized to be subtended by different cortical-subcortical circuits. This study tested whether interleaving the two tasks modifies latencies, due to switching between different modes of triggering. Two groups of healthy participants (21-29 vs. 39-55 years) made horizontal and vertical saccades in gap, overlap, and mixed tasks; saccades were recorded with the Eyelink. Both groups showed shorter latencies in the gap task, i.e. a robust gap effect and systematic differences between directions. For young adults, interleaving tasks made the latencies shorter or longer depending on direction, while for middle-age adults, latencies became longer for all directions. Our observations can be explained in the context of models such as that of Brown et al. (Neural Netw 17:471-510, 2004), which proposed that different combinations of frontal eye field (FEF) layers, interacting with cortico-subcortical areas, control saccade triggering in gap and overlap trials. Moreover, we suggest that in early adulthood, the FEF is functioning optimally; frequent changes of activity in the FEF can be beneficial, leading to shorter latencies, at least for some directions. However, for middle-age adults, frequent changes of activity of a less optimally functioning FEF can be time consuming. Studying the alternation of gap and overlap tasks provides a fine tool to explore development, aging and disease. |
Michael Wagner; Walter H. Ehrenstein; Thomas V. Papathomas Vergence in reverspective: Percept-driven versus data-driven eye movement control Journal Article In: Neuroscience Letters, vol. 449, no. 2, pp. 142–146, 2009. @article{Wagner2009, 'Reverspectives' (by artist Patrick Hughes) consist of truncated pyramids with their small faces closer to the viewer, allowing realistic scenes to be painted on them. Because their pictorial perspective reverses the physical depth arrangement, reverspectives provide a bistable paradigm of two radically different, competing depth percepts, even when viewed binocularly: points that are physically further are perceived to be closer and vice versa. The key question addressed here is whether vergence is governed by the physical and/or the perceived depth of fixated targets. Vergence eye movements were recorded using the EyeLink II system under conditions optimized to obtain both the veridical and illusory depth percepts of a reverspective. Six gaze locations were signaled by LEDs placed at strategically selected depths on the stimulus surface. We obtained strong evidence that stable vergence fixations were governed by the percept: for the same LED position, eyes converged under veridical depth percepts and diverged under illusory percepts, thus rendering pictorial cues to be as effective as physical cues in vergence control. These results, obtained with stable fixations, do not disagree with earlier studies that found rapid fixational eye movements to be governed by physical depth cues. Together, these results allow us to speculate on the existence of at least two eye movement systems: an automatic, data-driven system for rapid successions of fixations; and a deliberate schema-driven vergence system that accounts for stable fixations based on the perceptual state of the observer. |
Z. I. Wang; Louis F. Dell'Osso Factors influencing pursuit ability in infantile nystagmus syndrome: Target timing and foveation capability. Journal Article In: Vision Research, vol. 49, no. 2, pp. 182–189, 2009. @article{Wang2009, We wished to determine the influential factors for Infantile Nystagmus Syndrome (INS) subjects' ability to acquire and pursue moving targets using predictions from the behavioral Ocular Motor System (OMS) model and data from INS subjects. Ocular motor simulations using a behavioral OMS model were performed in MATLAB Simulink. Eye-movement recordings were performed using a high-speed digital video system. We studied five INS subjects who pursued a 10°/s ramp target to both left and right. We measured their target-acquisition times based on position criteria. The following parameters were studied: Lt (measured from the target-ramp initiation to the first on-target foveation period), target pursuit direction, and foveation-period pursuit gain. Analyses and simulations were performed in MATLAB environment using OMLAB software (OMtools, download from http://www.omlab.org). Ramp-target timing influenced target-acquisition time; the closer to the intrinsic saccades in the waveform the ramp stimuli started, the longer was Lt. However, arriving at the target position may not guarantee its foveation. Foveation-period pursuit gains vs. target or slow-phase direction had an idiosyncratic relationship for each subject. Adjustments to the model's Fixation subsystem reproduced the idiosyncratic foveation-period pursuit gains; the gain of the Smooth Pursuit subsystem was maintained at its normal value. The model output predicted a steady-state error when target initiation occurred during intrinsic saccades, consistent with human data. We conclude that INS subjects acquire ramp targets with longer latency for target initiations during or near the intrinsic saccades, consistent with the findings in our step-stimuli timing study. This effect might be due to the interaction between the saccadic and pursuit systems. The combined effects of target timing and Fixation-subsystem gain determined how fast and how well the INS subjects pursued ramp stimuli during their foveations periods (i.e., their foveation-period pursuit gain). The OMS model again demonstrated its behavioral characteristics and prediction capabilities (e.g., steady-state error) and revealed an important interaction between the Fixation and Smooth Pursuit subsystems. |
Gregory L. West; Timothy N. Welsh; Jay Pratt Saccadic trajectories receive online correction: Evidence for a feedback-based system of oculomotor control Journal Article In: Journal of Motor Behavior, vol. 41, no. 2, pp. 117–126, 2009. @article{West2009, Although a considerable amount of research has investigated the planning and production of saccadic eye movements, it remains unclear whether (a) central planning processes prior to movement onset largely determine these eye movements or (b) they receive online correction during the actual trajectory. To investigate this issue, the authors measured the spatial position of the eye at specific kinematic markers during saccadic movements (i.e., peak acceleration, peak velocity, peak deceleration, saccade endpoint). In 2 experiments, the authors examined saccades ranging in amplitude from 4 to 20 degrees and computed the variability profiles (SD) of eye position at each kinematic marker and the proportion of explained variance (R2) between each kinematic marker and the saccade endpoint. In Experiment 1, the authors examined differences in the kinematic signature of saccadic online control between eye movements made in gap or overlap conditions. In Experiment 2, the authors examined the online control of saccades made from stored target information after delays of 500, 1,500, and 3,500 ms. Findings evince a robust and consistent feedback-based system of online oculomotor control during saccadic eye movements. |
Tanya Blekher; Marjorie R. Weaver; Xueya Cai; Siu L. Hui; Jeanine Marshall; Jacqueline Gray Jackson; Joanne Wojcieszek; Robert D. Yee; Tatiana M. Foroud Test-retest reliability of saccadic measures in subjects at risk for Huntington disease Journal Article In: Investigative Ophthalmology & Visual Science, vol. 50, no. 12, pp. 5707–5711, 2009. @article{Blekher2009, PURPOSE Abnormalities in saccades appear to be sensitive and specific biomarkers in the prediagnostic stages of Huntington disease (HD). The goal of this study was to evaluate test-retest reliability of saccadic measures in prediagnostic carriers of the HD gene expansion (PDHD) and normal controls (NC). METHODS The study sample included 9 PDHD and 12 NC who completed two study visits within an approximate 1-month interval. At the first visit, all participants completed a uniform clinical evaluation. A high-resolution, video-based system was used to record eye movements during completion of a battery of visually guided, antisaccade, and memory-guided tasks. Latency, velocity, gain, and percentage of errors were quantified. Test-retest reliability was estimated by calculating the intraclass correlation (ICC) of the saccade measures collected at the first and second visits. In addition, an equality test based on Fisher's z-transformation was used to evaluate the effects of group (PDHD and NC) and the subject's sex on ICC. RESULTS The percentage of errors showed moderate to high reliability in the antisaccade and memory-guided tasks (ICC = 0.64-0.93). The latency of the saccades also demonstrated moderate to high reliability (ICC = 0.55-0.87) across all tasks. The velocity and gain of the saccades showed moderate reliability. The ICC was similar in the PDHD and NC groups. There was no significant effect of sex on the ICC. CONCLUSIONS Good reliability of saccadic latency and percentage of errors in both antisaccade and memory-guided tasks suggests that these measures could serve as biomarkers to evaluate progression in HD. |
Tanya Blekher; Marjorie R. Weaver; Jeanine Marshall; Siu L. Hui; Jacqueline Gray Jackson; Julie C. Stout; Xabier Beristain; Joanne Wojcieszek; Robert D. Yee; Tatiana M. Foroud Visual scanning and cognitive performance in prediagnostic and early-stage Huntington's disease Journal Article In: Movement Disorders, vol. 24, no. 4, pp. 533–540, 2009. @article{Blekher2009a, The objective of this study was to evaluate visual scanning strategies in carriers of the Huntington disease (HD) gene expansion and to test whether there is an association between measures of visual scanning and cognitive performance. The study sample included control (NC |
Tanya Blekher; Marjorie R. Weaver; Jason Rupp; William C. Nichols; Siu L. Hui; Jacqueline Gray; Robert D. Yee; Joanne Wojcieszek; Tatiana M. Foroud Multiple step pattern as a biomarker in Parkinson disease Journal Article In: Parkinsonism and Related Disorders, vol. 15, no. 7, pp. 506–510, 2009. @article{Blekher2009b, Objective: To evaluate quantitative measures of saccades as possible biomarkers in early stages of Parkinson disease (PD) and in a population at-risk for PD. Methods: The study sample (n = 68) included mildly to moderately affected PD patients, their unaffected siblings, and control individuals. All participants completed a clinical evaluation by a movement disorder neurologist. Genotyping of the G2019S mutation in the LRRK2 gene was performed in the PD patients and their unaffected siblings. A high resolution, video-based eye tracking system was employed to record eye positions during a battery of visually guided, anti-saccadic (AS), and two memory-guided (MG) tasks. Saccade measures (latency, velocity, gain, error rate, and multiple step pattern) were quantified. Results: PD patients and a subgroup of their unaffected siblings had an abnormally high incidence of multiple step patterns (MSP) and reduced gain of saccades as compared with controls. The abnormalities were most pronounced in the more challenging version of the MG task. For this task, the MSP measure demonstrated good sensitivity (87%) and excellent specificity (96%) in the ability to discriminate PD patients from controls. PD patients and their siblings also made more errors in the AS task. Conclusions: Abnormalities in eye movement measures appear to be sensitive and specific measures in PD patients as well as a subset of those at-risk for PD. The inclusion of quantitative laboratory testing of saccadic movements may increase the sensitivity of the neurological examination to identify individuals who are at greater risk for PD. |
Muriel T. N. Panouillères; Tiffany Weiss; Christian Urquizar; Roméo Salemme; Douglas P. Munoz; Denis Pélisson Behavioural evidence of separate adaptation mechanisms controlling saccade amplitude lengthening and shortening Journal Article In: Journal of Neurophysiology, vol. 101, no. 3, pp. 1550–1559, 2009. @article{Panouilleres2009, The accuracy of saccadic eye movements is maintained over the long term by adaptation mechanisms that decrease or increase saccade amplitude. It is still unknown whether these opposite adaptive changes rely on common mechanisms. Here, a double-step target paradigm was used to adaptively decrease (backward second target step) or increase (forward step) the amplitude of reactive saccades in one direction only. To test which sensorimotor transformation stages are subjected to these adaptive changes, we measured their transfer to antisaccades in which sensory and motor vectors are spatially dissociated. In the backward adaptation condition, all subjects showed a significant amplitude decrease for adapted prosaccades and a significant transfer of adaptation to antisaccades performed in the adapted direction, but not to oppositely directed antisaccades elicited by a target jump in the adapted direction. In the forward adaptation condition, only 14 of 19 subjects showed a significant amplitude increase for prosaccades and no significant adaptation transfer to antisaccades was detected in either the adapted or nonadapted direction. These findings suggest that, whereas the level(s) of forward adaptation cannot be resolved, the mechanisms involved in backward adaptation of reactive saccades take place at a sensorimotor level downstream from the vector inversion process of antisaccades and differ markedly from those involved in forward adaptation. |
T. Roth; Alexander N. Sokolov; A. Messias; P. Roth; M. Weller; Susanne Trauzettel-Klosinski Comparing explorative saccade and flicker training in hemianopia: A randomized controlled study Journal Article In: Neurology, vol. 72, pp. 324–331, 2009. @article{Roth2009, Objective: Patients with homonymous hemianopia are disabled on everyday exploratory activities. We examined whether explorative saccade training (EST), compared with flicker-stimulation training (FT), would selectively improve saccadic behavior on the patients' blind side and benefit performance on natural exploratory tasks. Methods: Twenty-eight hemianopic patients were randomly assigned to distinct groups performing for 6 weeks either EST (a digit-search task) or FT (blind-hemifield stimulation by flickering letters). Outcome variables (response times [RTs] during natural search, number of fixations during natural scene exploration, fixation stability, visual fields, and quality-of-life scores) were collected before, directly after, and 6 weeks after training. Results: EST yielded a reduced (post/pre, 47%) digit-search RT for the blind side. Natural search RT decreased (post/pre, 23%) on the blind side but not on the seeing side. After FT, both sides' RT remained unchanged. Only with EST did the number of fixations during natural scene exploration increase toward the blind and decrease on the seeing side (follow-up/pre difference, 238%). Even with the target located on the seeing side, after EST more fixations occurred toward the blind side. The EST group showed decreased (post/pre, 43%) fixation stability and increased (post/pre, 482%) asymmetry of fixations toward the blind side. Visual field size remained constant after both treatments. EST patients reported improvements in social domain. Conclusions: Explorative saccade training selectively improves saccadic behavior, natural search, and scene exploration on the blind side. Flicker-stimulation training does not improve saccadic behavior or visual fields. The findings show substantial benefits of compensatory exploration training, including subjective improvements in mastering daily-life activities, in a randomized controlled trial. |
Alexander C. Schütz; Doris I. Braun; Karl R. Gegenfurtner Chromatic contrast sensitivity during optokinetic nystagmus, visually enhanced vestibulo-ocular reflex, and smooth pursuit eye movements Journal Article In: Journal of Neurophysiology, vol. 101, no. 5, pp. 2317–2327, 2009. @article{Schuetz2009, Recently we showed that sensitivity for chromatic- and high-spatial frequency luminance stimuli is enhanced during smooth-pursuit eye movements (SPEMs). Here we investigated whether this enhancement is a general property of slow eye movements. Besides SPEM there are two other classes of eye movements that operate in a similar range of eye velocities: the optokinetic nystagmus (OKN) is a reflexive pattern of alternating fast and slow eye movements elicited by wide-field visual motion and the vestibulo-ocular reflex (VOR) stabilizes the gaze during head movements. In a natural environment all three classes of eye movements act synergistically to allow clear central vision during self- and object motion. To test whether the same improvement of chromatic sensitivity occurs during all of these eye movements, we measured human detection performance of chromatic and luminance line stimuli during OKN and contrast sensitivity during VOR and SPEM at comparable velocities. For comparison, performance in the same tasks was tested during fixation. During the slow phase of OKN we found a similar enhancement of chromatic detection rate like that during SPEM, whereas no enhancement was observable during VOR. This result indicates similarities between slow-phase OKN and SPEM, which are distinct from VOR. |
Alexander C. Schütz; Doris I. Braun; Karl R. Gegenfurtner Object recognition during foveating eye movements Journal Article In: Vision Research, vol. 49, no. 18, pp. 2241–2253, 2009. @article{Schuetz2009a, We studied how saccadic and smooth pursuit eye movements affect the recognition of briefly presented letters appearing within the eye movement target. First we compared the recognition performance during steady-state pursuit and during fixation. Single letters were presented for seven different durations ranging from 10 to 400 ms and four contrast levels ranging from 5% to 40%. For both types of eye movements the recognition rates increased with duration and contrast, but they were on average 11% lower during pursuit. In daily life humans use a combination of saccadic and smooth pursuit eye movements to foveate a peripheral moving object. To investigate this more natural situation, we presented a peripheral target that was either stationary or moving horizontally, above or below the fixation spot. Participants were asked to saccade to the target and to keep it foveated. The letters were presented at different times relative to the first target directed saccade. As would be expected from retinal masking and motion blur during saccades, the discrimination performance increased with increasing post-saccadic delay. If the target moved and the saccade was followed by pursuit, letter recognition performance was on average 16% lower than if the target was stationary and the saccade was followed by fixation. |
Alexander C. Schütz; Doris I. Braun; Karl R. Gegenfurtner; Alexander C. Schu Improved visual sensitivity during smooth pursuit eye movements: Temporal and spatial characteristics Journal Article In: Visual Neuroscience, vol. 26, no. 3, pp. 329–340, 2009. @article{Schuetz2009b, Recently, we showed that contrast sensitivity for color and high–spatial frequency luminance stimuli is enhanced during smooth pursuit eye movements (Schütz et al., 2008). In this study, we investigated the enhancement over a wide range of temporal and spatial frequencies. In Experiment 1, we measured the temporal impulse response function (TIRF) for colored stimuli. The TIRF for pursuit and fixation differed mostly with respect to the gain but not with respect to the natural temporal frequency. Hence, the sensitivity enhancement seems to be rather independent of the temporal frequency of the stimuli. In Experiment 2, we measured the spatial contrast sensitivity function for luminance-defined Gabor patches with spatial frequencies ranging from 0.2 to 7 cpd. We found a sensitivity improvement during pursuit for spatial frequencies above 2–3 cpd. Between 0.5 and 3 cpd, sensitivity was impaired by smooth pursuit eye movements, but no consistent difference was observed below 0.5 cpd. The results of both experiments are consistent with an increased contrast gain of the parvocellular retinogeniculate pathway. |
David Souto; Dirk Kerzel Evidence for an attentional component in saccadic inhibition of return Journal Article In: Experimental Brain Research, vol. 195, no. 4, pp. 531–540, 2009. @article{Souto2009, After presentation of a peripheral cue, facilitation at the cued location is followed by inhibition of return (IOR). It has been recently proposed that IOR may originate at different processing stages for manual and ocular responses, with manual IOR resulting from inhibited attentional orienting, and ocular IOR resulting form inhibited motor preparation. Contrary to this interpretation, we found an effect of target contrast on saccadic IOR. The effect of contrast decreased with increasing reaction times (RTs) for saccades, but not for manual key-press responses. This may have masked the effect of contrast on IOR with saccades in previous studies (Hunt and Kingstone in J Exp Psychol Hum Percept Perform 29:1068-1074, 2003) because only mean RTs were considered. We also found that background luminance strongly influenced the effects of gap and target contrast on IOR. |
David Souto; Dirk Kerzel Involuntary cueing effects during smooth pursuit: Facilitation and inhibition of return in oculocentric coordinates Journal Article In: Experimental Brain Research, vol. 192, no. 1, pp. 25–31, 2009. @article{Souto2009a, Peripheral cues induce facilitation with short cue-target intervals and inhibition of return (IOR) with long cue-target intervals. Modulations of facilitation and IOR by continuous displacements of the eye or the cued stimuli are poorly understood. Previously, the retinal coordinates of the cued location were changed by saccadic or smooth pursuit eye movements during the cue-target interval. In contrast, we probed the relevant coordinates for facilitation and IOR by orthogonally varying object motion (stationary, moving) and eye movement (fixation, smooth pursuit). In the pursuit conditions, cue and target were presented during the ongoing eye movement and observers made a saccade to the target. Importantly, we found facilitation and IOR of similar size during smooth pursuit and fixation. The results suggest that involuntary orienting is possible even when attention has to be allocated to the moving target during smooth pursuit. Comparison of conditions with stabilized and moving objects suggest an oculocentric basis for facilitation as well as inhibition. Facilitation and IOR were reduced with objects that moved on the retina both with smooth pursuit and eye fixation. |
Martin Stritzke; Julia Trommershäuser; Karl R. Gegenfurtner Effects of salience and reward information during saccadic decisions under risk Journal Article In: Journal of the Optical Society of America A, vol. 26, no. 11, pp. B1–B13, 2009. @article{Stritzke2009, Previous work has demonstrated that humans select visuomotor strategies maximizing expected gain during speeded hand movements under risk; see, e.g., [Trends Cogn. Sci. 12, 291 (2008)]; [Glimcher, eds., Neuroeconomics: Decision Making and the Brain (Elsevier, 2008), p. 95]. Here we report a similar study in which we recorded saccadic eye movements in a saccadic decision task in which monetary rewards and losses were associated with the final position of the eye movement. Saccades into a color-coded target region won points; saccades into a partially overlapping or abutting penalty region could yield a loss. The points won during the experiment were converted into a small monetary bonus at the end of the experiment. We compared participants' winnings to the score of an optimal observer maximizing expected gain that was calculated based on each participant's saccadic endpoint variability, similar to a recent model of optimal movement planning under risk [J. Opt. Soc. Am. A 20, 1419 (2003)]; [Spatial Vis. 16, 255 (2003)]. We used three different experimental paradigms with different interstimulus intervals (Gap, No Gap, and Overlap) to manipulate saccadic latencies and a fourth experiment (Memory) with a prolonged 500 ms delay period. Our results show that our subjects took the reward information, as specified by the different penalties, into account when making saccades and fixated onto or very close to the target region and less into the penalty region. However, the selected strategies differed significantly from optimal strategies maximizing expected gain in conditions when the magnitude of reward or penalty was changed. Furthermore, scores were notably affected by stimulus saliency. They were higher when the target region was filled and the penalty region outlined by a thin line, as compared to conditions in which the target was indicated by a less salient stimulus. Scores were particularly poor in trials with the shortest latencies (120-140 ms) mostly obtained in the Gap paradigm. At longer latencies scores improved considerably for latencies longer than 160 ms. This was in line with an improvement in accuracy for single targets up to 160 ms. Our results indicate that processing both of reward information and of stimulus saliency affect the programming of saccades, with a dominating contribution of stimulus saliency for eye movements with faster latencies. |
Abtine Tavassoli; Dario L. Ringach Dynamics of smooth pursuit maintenance Journal Article In: Journal of Neurophysiology, vol. 102, no. 1, pp. 110–118, 2009. @article{Tavassoli2009, Smooth pursuit eye movements allow the approximate stabilization of a moving visual target on the retina. To study the dynamics of smooth pursuit, we measured eye velocity during the visual tracking of a Gabor target moving at a constant velocity plus a noisy perturbation term. The optimal linear filter linking fluctuations in target velocity to evoked fluctuations in eye velocity was computed. These filters predicted eye velocity to novel stimuli in the 0- to 15-Hz band with good accuracy, showing that pursuit maintenance is approximately linear under these conditions. The shape of the filters were indicative of fast dynamics, with pure delays of merely approximately 67 ms, times-to-peak of approximately 115 ms, and effective integration times of approximately 45 ms. The gain of the system, reflected in the amplitude of the filters, was inversely proportional to the size of the velocity fluctuations and independent of the target mean speed. A modest slow-down of the dynamics was observed as the contrast of the target decreased. Finally, the temporal filters recovered during fixation and pursuit were similar in shape, supporting the notion that they might share a common underlying circuitry. These findings show that the visual tracking of moving objects by the human eye includes a reflexive-like pathway with high contrast sensitivity and fast dynamics. |
Dagmar A. Wismeijer; Casper J. Erkelens The effect of changing size on vergence is mediated by changing disparity Journal Article In: Journal of vision, vol. 9, no. 13, pp. 12 1–10, 2009. @article{Wismeijer2009, In this study, we investigated the effect of changing size on vergence. Erkelens and Regan (1986) proposed that this cue to motion in depth affects vergence in a similar way as it affects perception. The measured effect on vergence was small and we wondered why the vergence system would use changing size as an additional cue to changing disparity. To elucidate the effect of changing size on vergence, we used an annulus carrying both changing size and changing disparity signals to motion in depth. The cues were either congruent or signaled a different depth. The results showed that vergence was affected by changing size, however in an opposite way than that perception was affected. These results were incongruent with those reported by Erkelens and Regan (1986). We therefore additionally measured the effects on vergence of the individual parameters associated with changing size, i.e., stimulus area, retinal eccentricity, and luminance. Stimulus (retinal) eccentricity was inversely related to vergence gain. Luminance, on the other hand, had a smaller but positive relation to vergence gain. Thus, changing size affected the disparity signal two-fold: it changed the retinal location of the disparity signal and it changed the strength of the disparity signal (luminance change). These effects of changing size on disparity can explain both our results (change in retinal location of the disparity signal) and those of Erkelens and Regan (1986; change in luminance). We thus conclude that changing size did not in itself contribute to vergence, rather its effect on vergence was mediated by disparity. |
Eckart Zimmermann; Markus Lappe Mislocalization of flashed and stationary visual stimuli after adaptation of reactive and scanning saccades Journal Article In: Journal of Neuroscience, vol. 29, no. 35, pp. 11055–11064, 2009. @article{Zimmermann2009, When we look around and register the location of visual objects, our oculomotor system continuously prepares targets for saccadic eye movements. The preparation of saccade targets may be directly involved in the perception of object location because modification of saccade amplitude by saccade adaptation leads to a distortion of the visual localization of briefly flashed spatial probes. Here, we investigated effects of adaptation on the localization of continuously visible objects. We compared adaptation-induced mislocalization of probes that were present for 20 ms during the saccade preparation period and of probes that were present for >1 s before saccade initiation. We studied the mislocalization of these probes for two different saccade types, reactive saccades to a suddenly appearing target and scanning saccades in the self-paced viewing of a stationary scene. Adaptation of reactive saccades induced mislocalization of flashed probes. Adaptation of scanning saccades induced in addition also mislocalization of stationary objects. The mislocalization occurred in the absence of visual landmarks and must therefore originate from the change in saccade motor parameters. After adaptation of one type of saccade, the saccade amplitude change and the mislocalization transferred only weakly to the other saccade type. Mislocalization of flashed and stationary probes thus followed the selectivity of saccade adaptation. Since the generation and adaptation of reactive and scanning saccades are known to involve partially different brain mechanisms, our results suggest that visual localization of objects in space is linked to saccade targeting at multiple sites in the brain. |
Korbinian Moeller; S. Neuburger; L. Kaufmann; K. Landerl; Hans-Christoph Nuerk Basic number processing deficits in developmental dyscalculia: Evidence from eye tracking Journal Article In: Cognitive Development, vol. 24, no. 4, pp. 371–386, 2009. @article{Moeller2009, Recent research suggests that developmental dyscalculia is associated with a subitizing deficit (i.e., the inability to quickly enumerate small sets of up to 3 objects). However, the nature of this deficit has not previously been investigated. In the present study the eye-tracking methodology was employed to clarify whether (a) the subitizing deficit of two boys with dyscalculia resulted from a general slowing in the access to magnitude representation, or (b) children with dyscalculia resort to a back-up counting strategy even for small object sets. In a dot-counting task, a standard problem size effect for the number of fixations required to encode the presented numerosity within the subitizing range was observed. Together with the finding that problem size had no impact on the average fixation duration, this result suggested that children with dyscalculia may indeed have to count, while typically developing controls are able to enumerate the number of dots in parallel, i.e., subitize. Implications for the understanding of developmental dyscalculia are considered. |
René M. Müri; D. Cazzoli; Thomas Nyffeler; Tobias Pflugshaupt Visual exploration pattern in hemineglect Journal Article In: Psychological Research, vol. 73, no. 2, pp. 147–157, 2009. @article{Mueri2009, The analysis of eye movement parameters in visual neglect such as cumulative fixation duration, saccade amplitude, or the numbers of saccades has been used to probe attention deficits in neglect patients, since the pattern of exploratory eye movements has been taken as a strong index of attention distribution. The current overview of the literature of visual neglect has its emphasis on studies dealing with eye movement and exploration analysis. We present our own results in 15 neglect patients. The free exploration behavior was analyzed in these patients presenting 32 naturalistic color photographs of everyday scenes. Cumulative fixation duration, spatial distribution of fixations in the horizontal and vertical plane, the number and amplitude of exploratory saccades was analyzed and compared with the results of an age-matched control group. A main result of our study was that in neglect patients, fixation distribution of free exploration of natural scenes is not only influenced by the left-right bias in the horizontal direction but also by the vertical direction. |
Tara H. Cronin; Richard W. Hertle; Hiroshi Ishikawa; Joel S. Schuman Spectral domain optical coherence tomography for detection of foveal morphology in patients with nystagmus Journal Article In: Journal of AAPOS, vol. 13, no. 6, pp. 563–566, 2009. @article{Cronin2009, Purpose: To evaluate the feasibility of spectral domain optical coherence tomography (SD-OCT) macular scanning as a means of studying the afferent visual system in nystagmus patients. Methods: Nystagmus patients who underwent SD-OCT, clinical evaluation, and eye movement recordings were recruited for this prospective, single-center, noncomparative study. Three SD-OCT macular three-dimensional cube scans per eye (200 × 200 × 1024 samplings in a 6 × 6 mm region) were obtained for qualitative retinal morphology analysis. Results: Nineteen patients (6-68 years; average, 19 years) were analyzed. Of these, 17 patients had infantile nystagmus syndrome, and 2 had fusion maldevelopment nystagmus; 17 patients (89%) had associated sensory system abnormalities, including 9 (47%) with albinism. Macular images were successfully obtained in all but 1 patient (95%). Of the 8 successfully imaged oculocutaneous patients, 7 patients demonstrated "fovea plana," and all demonstrated abnormal morphology. Conclusion: SD-OCT reliably provides detailed structural imaging of the fovea in nystagmus patients.A figure is presentedA figure is presented. © 2009 American Association for Pediatric Ophthalmology and Strabismus. |
Kirsten A. Dalrymple; Walter F. Bischof; David Cameron; Jason J. S. Barton; Alan Kingstone Global perception in simultanagnosia is not as simple as a game of connect-the-dots Journal Article In: Vision Research, vol. 49, no. 14, pp. 1901–1908, 2009. @article{Dalrymple2009, Simultanagnosia is a neuropsychological disorder characterized by a restriction of visuospatial attention. In addition, patients are able to identify local elements of a scene, but not the global whole. This may be due to a failure to scan and assemble local elements into a global whole (i.e. connect-the-dots). We monitored the eye movements of a simultanagnosic patient while she identified local and global elements of hierarchical letters. Scanning each local element was not necessary, nor sufficient, for successful global level identification. Our results argue against a connect-the-dots strategy of global identification and suggest that residual global processing may be occurring. |
Sarah Bate; Catherine Haslam; Ashok Jansari; Timothy L. Hodgson Covert face recognition relies on affective valence in congenital prosopagnosia Journal Article In: Cognitive Neuropsychology, vol. 26, no. 4, pp. 391–411, 2009. @article{Bate2009, Dominant accounts of covert recognition in prosopagnosia assume subthreshold activation of face representations created prior to onset of the disorder. Yet, such accounts cannot explain covert recognition in congenital prosopagnosia, where the impairment is present from birth. Alternatively, covert recognition may rely on affective valence, yet no study has explored this possibility. The current study addressed this issue in 3 individuals with congenital prosopagnosia, using measures of the scanpath to indicate recognition. Participants were asked to memorize 30 faces paired with descriptions of aggressive, nice, or neutral behaviours. In a later recognition test, eye movements were monitored while participants discriminated studied from novel faces. Sampling was reduced for studied–nice compared to studied–aggressive faces, and performance for studied–neutral and novel faces fell between these two conditions. This pattern of findings suggests that (a) positive emotion can facilitate processing in prosopagnosia, and (b) covert recognition may rely on emotional valence rather than familiarity. |
Tobias Pflugshaupt; Klemens Gutbrod; Pascal Wurtz; Roman Von Wartburg; Thomas Nyffeler; Bianca De Haan; Hans-Otto Karnath; René M. Mueri About the role of visual field defects in pure alexia Journal Article In: Brain, vol. 132, no. 7, pp. 1907–1917, 2009. @article{Pflugshaupt2009, Pure alexia is an acquired reading disorder characterized by a disproportionate prolongation of reading time as a function of word length. Although the vast majority of cases reported in the literature show a right-sided visual defect, little is known about the contribution of this low-level visual impairment to their reading difficulties. The present study was aimed at investigating this issue by comparing eye movement patterns during text reading in six patients with pure alexia with those of six patients with hemianopic dyslexia showing similar right-sided visual field defects. We found that the role of the field defect in the reading difficulties of pure alexics was highly deficit-specific. While the amplitude of rightward saccades during text reading seems largely determined by the restricted visual field, other visuo-motor impairments—particularly the pronounced increases in fixation frequency and viewing time as a function of word length—may have little to do with their visual field defect. In addition, subtracting the lesions of the hemianopic dyslexics from those found in pure alexics revealed the largest group differences in posterior parts of the left fusiform gyrus, occipito-temporal sulcus and inferior temporal gyrus. These regions included the coordinate assigned to the centre of the visual word form area in healthy adults, which provides further evidence for a relation between pure alexia and a damaged visual word form area. Finally, we propose a list of three criteria that may improve the differential diagnosis of pure alexia and allow appropriate therapy recommendations. |
Tobias Pflugshaupt; Roman Wartburg; Pascal Wurtz; Silvia Chaves; Anouk Déruaz; Thomas Nyffeler; Sebastian Arx; Mathias Luethi; Dario Cazzoli; René M. Mueri Linking physiology with behaviour: Functional specialisation of the visual field is reflected in gaze patterns during visual search Journal Article In: Vision Research, vol. 49, no. 2, pp. 237–248, 2009. @article{Pflugshaupt2009a, Based on neurophysiological findings and a grid to score binocular visual field function, two hypotheses concerning the spatial distribution of fixations during visual search were tested and confirmed in healthy participants and patients with homonymous visual field defects. Both groups showed significant biases of fixations and viewing time towards the centre of the screen and the upper screen half. Patients displayed a third bias towards the side of their field defect, which represents oculomotor compensation. Moreover, significant correlations between the extent of these three biases and search performance were found. Our findings suggest a new, more dynamic view of how functional specialisation of the visual field influences behaviour. |
Elmar H. Pinkhardt; Jan Kassubek; Sigurd Süssmuth; Albert C. Ludolph; Wolfgang Becker; Reinhart Jürgens Comparison of smooth pursuit eye movement deficits in multiple system atrophy and Parkinson's disease Journal Article In: Journal of Neurology, vol. 256, no. 9, pp. 1438–1446, 2009. @article{Pinkhardt2009, Because of the large overlap and quantitative similarity of eye movement alterations in Parkinson's disease (PD) and multiple system atrophy (MSA), a measurement of eye movement is generally not considered helpful for the differential diagnosis. However, in view of the pathophysiological differences between MSA and PD as well as between the cerebellar (MSA-C) and Parkinsonian (MSA-P) subtypes of MSA, we wondered whether a detailed investigation of oculomotor performance would unravel parameters that could help to differentiate between these entities. We recorded eye movements during sinusoidal pursuit tracking by means of video-oculography in 11 cases of MSA-P, 8 cases of MSA-C and 27 cases of PD and compared them to 23 healthy controls (CTL). The gain of the smooth pursuit eye movement (SPEM) component exhibited significant group differences between each of the three subject groups (MSA, PD, controls) but not between MSA-P and MSA-C. The similarity of pursuit impairment in MSA-P and in MSA-C suggests a commencement of cerebellar pathology in MSA-P despite the lack of clinical signs. Otherwise, SPEM gain was of little use for differential diagnosis between MSA and PD because of wide overlap. However, inspection of the saccadic component of pursuit tracking revealed that in MSA saccades typically correct for position errors accumulated during SPEM epochs ("catch-up saccades"), whereas in PD, saccades were often directed toward future target positions ("anticipatory saccades"). The differences in pursuit tracking between PD and MSA were large enough to warrant their use as ancillary diagnostic criteria for the distinction between these disorders. |
L. Elliot Hong; Kathleen A. Turano; Hugh B. O'Neill; Lei Hao; Ikwunga Wonodi; Robert P. McMahon; Gunvant K. Thaker Is motion perception deficit in Schizophrenia a consequence of eye-tracking abnormality? Journal Article In: Biological Psychiatry, vol. 65, no. 12, pp. 1079–1085, 2009. @article{Hong2009, Background: Studies have shown that schizophrenia patients have motion perception deficit, which was thought to cause eye-tracking abnormality in schizophrenia. However, eye movement closely interacts with motion perception. The known eye-tracking difficulties in schizophrenia patients may interact with their motion perception. Methods: Two speed discrimination experiments were conducted in a within-subject design. In experiment 1, the stimulus duration was 150 msec to minimize the chance of eye-tracking occurrence. In experiment 2, the duration was increased to 300 msec, increasing the possibility of eye movement intrusion. Regular eye-tracking performance was evaluated in a third experiment. Results: At 150 msec, speed discrimination thresholds did not differ between schizophrenia patients (n = 38) and control subjects (n = 33). At 300 msec, patients had significantly higher thresholds than control subjects (p = .03). Furthermore, frequencies of eye tracking during the 300 msec stimulus were significantly correlated with speed discrimination in control subjects (p = .01) but not in patients, suggesting that eye-tracking initiation may benefit control subjects but not patients. The frequency of eye tracking during speed discrimination was not significantly related to regular eye-tracking performance. Conclusions: Speed discrimination, per se, is not impaired in schizophrenia patients. The observed abnormality appears to be a consequence of impairment in generating or integrating the feedback information from eye movements. This study introduces a novel approach to motion perception studies and highlights the importance of concurrently measuring eye movements to understand interactions between these two systems; the results argue for a conceptual revision regarding motion perception abnormality in schizophrenia. |
Jonathan B. Jacobs; Louis F. Dell'Osso; Zhong I. Wang; Gregory M. Acland; Jean Bennett Using the NAFX to measure the effectiveness over time of gene therapy in canine LCA Journal Article In: Investigative Ophthalmology & Visual Science, vol. 50, no. 10, pp. 4685–4692, 2009. @article{Jacobs2009, PURPOSE: To use ocular motility recordings to determine the changes over time of infantile nystagmus syndrome (INS) in RPE65-deficient canines with Leber Congenital Amaurosis (LCA) and assess the time course of the recalibration of the ocular motor system (OMS). METHODS: Nine dogs were treated bilaterally with AAV-RPE65. A second cohort of four dogs was treated with AAV2.RPE65, an optimized vector. Their fixation eye movements were recorded before treatment and at 4-week intervals for 3 months, by using high-speed (500 Hz) digital videography. The dogs were suspended in a sling and encouraged to fixate on distant (57 inches) targets at gaze angles varying between +/-15 degrees horizontally and +/-10 degrees vertically. The records for each eye were examined for qualitative changes in waveform and for quantitative changes in centralisation with the expanded nystagmus acuity function (NAFX) and compared with ERG results for restoration of receptor function. RESULTS: First group: Before treatment, five of the dogs had clinically apparent INS with jerk, pendular, or both waveforms and with peak-to-peak amplitudes as great as 15 degrees . One dog had intermittent nystagmus. At the 1- and 2-month examinations, no change in nystagmus waveform or NAFX was observed in any of the initial dogs, while at 10 weeks, one dog treated bilaterally with the standard dosage showed reduced nystagmus in only one eye. The other eye did not respond to treatment, as confirmed by ERG. This result was unexpected since it was previously documented that unilateral treatment leads to bilateral reduction of INS. The other dog treated with the standard dosage showed no reduction of its small-amplitude, high-frequency pendular nystagmus despite positive ERG responses. Second group: Only one dog of the four had clinically detectable INS, similar in characteristics to that seen in the affected dogs of the first group. Unlike any previous dog studied, this one showed a damping of the nystagmus within the first 4 weeks after treatment. CONCLUSIONS: In all but one of the cases in which OMS recalibration occurred, as measured by the clinical appearance of nystagmus and by quantitative measurement using the NAFX, the improvement was apparent no sooner than 10 weeks after treatment. Longer term, dose-related studies are needed to determine the minimum necessary degree of restored receptor functionality, the duration after rescue for recalibration of the OMS, and the conditions under which recalibration information can successfully affect the contralateral eye. |
Tom Foulsham; Jason J. S. Barton; Alan Kingstone; Richard Dewhurst; Geoffrey Underwood Fixation and saliency during search of natural scenes: The case of visual agnosia Journal Article In: Neuropsychologia, vol. 47, no. 8-9, pp. 1994–2003, 2009. @article{Foulsham2009, Models of eye movement control in natural scenes often distinguish between stimulus-driven processes (which guide the eyes to visually salient regions) and those based on task and object knowledge (which depend on expectations or identification of objects and scene gist). In the present investigation, the eye movements of a patient with visual agnosia were recorded while she searched for objects within photographs of natural scenes and compared to those made by students and age-matched controls. Agnosia is assumed to disrupt the top-down knowledge available in this task, and so may increase the reliance on bottom-up cues. The patient's deficit in object recognition was seen in poor search performance and inefficient scanning. The low-level saliency of target objects had an effect on responses in visual agnosia, and the most salient region in the scene was more likely to be fixated by the patient than by controls. An analysis of model-predicted saliency at fixation locations indicated a closer match between fixations and low-level saliency in agnosia than in controls. These findings are discussed in relation to saliency-map models and the balance between high and low-level factors in eye guidance. |
Glenda Halliday; Maria Trinidad Herrero; Karen Murphy; Heather McCann; Francisco Ros-Bernal; Carlos Barcia; Hideo Mori; Francisco J. Blesa; Jose A. Obeso No Lewy pathology in monkeys with over 10 years of severe MPTP Parkinsonism Journal Article In: Movement Disorders, vol. 24, no. 10, pp. 1519–1545, 2009. @article{Halliday2009, The recent knowledge that 10 years after trans- plantation surviving human fetal neurons adopt the histopathology of Parkinson's disease suggests that Lewy body formation takes a decade to achieve. To determine whether similar histopathology occurs in 1-methyl-4- phenyl-1,2,3,6-tetrahydropyridine (MPTP)-primate models over a similar timeframe, the brains of two adult monkeys made parkinsonian in their youth with intermittent injections of MPTP were studied. Despite substantial nigral degeneration and increased α-synuclein immunoreactivity within surviving neurons, there was no evidence of Lewy body formation. This suggests that MPTP-induced oxidative stress and inflammation per se are not sufficient for Lewy body formation, or Lewy bodies are human specific |
Susanne Hertel; Andreas Sprenger; Christine Klein; Detlef Kömpf; Christoph Helmchen; Hubert Kimmig Different saccadic abnormalities in PINK1 mutation carriers and in patients with non-genetic Parkinson's disease Journal Article In: Journal of Neurology, vol. 256, no. 7, pp. 1192–1194, 2009. @article{Hertel2009, |
Richard W. Hertle; Joost Felius; Dongsheng Yang; Matthew Kaufman Eye muscle surgery for infantile nystagmus syndrome in the first two years of life Journal Article In: Clinical Ophthalmology, vol. 3, no. 1, pp. 615–624, 2009. @article{Hertle2009, PURPOSE: To report visual and elctrophysioloigcal effects of eye muscle surgery in young patients with infantile nystagmus syndrome (INS). METHODS: Prospective, interventional case cohort of 19 patients aged under 24 months who were operated on for combinations of strabismus, an anomalous head posture, and nystagmus. All patients were followed at least nine months. Outcome measures, part of an institutionally approved study, included Teller acuity, head position, strabismic deviation, and eye movement recordings, from which waveform types and a nystagmus optimal foveation fraction (NOFF). Computerized parametric and nonparametric statistical analysis of data were perfomed using standard software on both individual and group data. RESULTS: Age averaged 17.7 months (13.1-month follow-up). Thirteen (68%) patients had associated optic nerve or retinal disease. 42% had amblyopia, 68% had refractive errors. Group means in binocular Teller acuity (P < 0.05), strabismic deviation (P < 0.05), head posture (P < 0.001), and the NOFF measures (P < 0.01) from eye movement recordings improved in all patients. There was a change in null zone waveforms to more favorable jerk types. There were no reoperations or surgical complications. CONCLUSIONS: Surgery on the extraocular muscles in patients aged less than two years with INS results in improvements in multiple aspects of ocular motor and visual function. |
Jesse Hochstadt Set-shifting and the on-line processing of relative clauses in Parkinson's disease: Results from a novel eye-tracking method Journal Article In: Cortex, vol. 45, no. 8, pp. 991–1011, 2009. @article{Hochstadt2009, Past research indicates that in Parkinson's disease (PD), set-shifting deficits cause impaired comprehension of sentences containing restrictive relative clauses (RCs). Some research also suggests that verbal working memory deficits impair comprehension of long-distance (LD) dependencies in sentences with center-embedded RCs. To test whether these deficits impair comprehension by affecting on-line processing, we tracked patients' eye movements as they matched pictures with sentences with final- or center-embedded RCs (e.g., The queen was kicking the cook who was fat, The queen who was kicking the cook was thin) and active or passive verbs. Decreases in looks to distracters ruled out at the transitive verb (e.g., a cook kicking a queen) and the adjective (a fat queen kicking a thin cook) reflected how effective processing was at those points. Though patients showed greater difficulty comprehending center-embedded and passive sentences, set-shifting errors correlated with comprehension of all sentences. Consistent with this, patients with poorer comprehension exhibited impaired on-line processing of both center-embedded and final RCs (for which comprehension was better due to their grammatical simplicity), and these effects correlated with set-shifting errors. We consider two possible explanations for this apparently general RC-processing deficit. First, because RCs are infrequent, set-shifting may be needed to override the processor's expectations for higher-frequency structures. Second, because restrictive RCs typically refer to information already in the discourse context, set-shifting may be needed to redirect attention from linguistic foreground to background information. Eye-tracking data indicated no difficulty processing LD dependencies; correlations of verbal working memory with comprehension of passive and center-embedded sentences may reflect off-line use of memory. In trials with passive verbs, patients looked toward the verb distracter before even processing the verb. This effect was larger than that previously seen for young participants, suggesting that PD may amplify a normal bias to assume the subject noun is the agent. |
Naotsugu Tsuchiya; Farshad Moradi; Csilla Felsen; Madoka Yamazaki; Ralph Adolphs Intact rapid detection of fearful faces in the absence of the amygdala Journal Article In: Nature Neuroscience, vol. 12, no. 10, pp. 1224–1225, 2009. @article{Tsuchiya2009, The amygdala is thought to process fear-related stimuli rapidly and nonconsciously. We found that an individual with complete bilateral amygdala lesions, who cannot recognize fear from faces, nonetheless showed normal rapid detection and nonconscious processing of those same fearful faces. We conclude that the amygdala is not essential for early stages of fear processing but, instead, modulates recognition and social judgment. |
Gary S. Rubin; Mary P. Feely The role of eye movements during reading in patients with age-related macular degeneration (AMD) Journal Article In: Neuro-Ophthalmology, vol. 33, no. 3, pp. 120–126, 2009. @article{Rubin2009, AMD patients often have particular difficulty reading, even when the text is magnified to compensate for reduced visual acuity. This study explores whether reading performance can be explained by eye movement factors. Forty patients with advanced AMD were tested with a high-speed video eye tracker to evaluate fixation stability and saccadic eye movements. Reading speed was measured for standardized texts viewed at the critical print size. Visual acuity and contrast sensitivity were unrelated to reading speed, but fixation stability, proportion of regressive saccades and size of forward saccades were all significantly associated with reading performance, accounting for 74% of the variance. The implications of these findings for low-vision training programmes are discussed. |
Anil Kumar; Nagini Sarvananthan; Frank A. Proudlock; Mervyn G. Thomas; Eryl O. Roberts; Irene Gottlob Asperger syndrome associated with idiopathic infantile nystagmus-A report of 2 cases Journal Article In: Strabismus, vol. 17, no. 2, pp. 63–65, 2009. @article{Kumar2009, Asperger syndrome is a severe and chronic developmental disorder. It is closely associated with autism and is grouped under autism spectrum disorder (ASD). Various eye movement abnormalities in AS have been reported in literature such as increased errors and latencies on the antisaccadic task implicating dysfunction of the prefrontal cortex, impairment of the pursuit especially for targets presented in the right visual hemisphere, suggesting disturbance in the left extrastraite cortex. There are no reports in the literature of association between idiopathic infantile nystagmus (IIN) and AS. We report 2 cases of Asperger syndrome associated with idiopathic infantile nystagmus. |
Anil Kumar; Shery Thomas; Rebecca J. McLean; Frank A. Proudlock; Eryl O. Roberts; Mike Boggild; Irene Gottlob Treatment of acquired periodic alternating nystagmus with memantine: A case report Journal Article In: Clinical Neuropharmacology, vol. 32, no. 2, pp. 109–110, 2009. @article{Kumar2009a, We report a case of acquired periodic alternating nystagmus associated with common variable immunodeficiency and cutaneous sarcoid. The patient was initially treated with baclofen with minimal subjective improvement. We found a significant improvement in the patient's symptoms and nystagmus intensity after treatment with memantine. |
Anouk Lamontagne; Joyce Fung Gaze and postural reorientation in the control of locomotor steering after stroke Journal Article In: Neurorehabilitation and Neural Repair, vol. 23, no. 3, pp. 256–266, 2009. @article{Lamontagne2009, BACKGROUND: Steering of locomotion is a complex task involving stabilizing and anticipatory orienting behavior essential for the maintenance of balance and for establishing a stable frame of reference for future motor and sensory events. How these mechanisms are affected by stroke remains unknown. OBJECTIVES: To compare locomotor steering behavior between stroke and healthy individuals and to determine whether steering abilities are influenced by walking speed, turning direction and walking capacity in stroke individuals. METHODS: Gaze and body kinematics were recorded in 8 stroke and 7 healthy individuals while walking and turning in response to a visual cue. Horizontal orientation of gaze, head, thorax, pelvis, and feet with respect to spatial and heading coordinates were examined. RESULTS: Temporal and spatial coordination of gaze and body movements revealed stabilizing and anticipatory orienting mechanisms in the healthy individuals. Changing walking speed affected the onset time but not the sequencing of segment reorientation. In the individuals with stroke, abnormally large and uncoordinated head and gaze motion were observed. The sequence of gaze, head, thorax and pelvis horizontal reorientation also was also disrupted. Alterations in orienting behaviors were more pronounced at the slowest walking speeds and turning to the nonparetic side in 3 of the most severely disabled individuals. CONCLUSION: The results in this convenience sample of slow and faster walkers suggest that stroke alters the stabilizing and orienting behavior during steering of locomotion. Such alterations are not caused by the inherently slow walking speed, but rather by a combination of biomechanical factors and defective sensorimotor integration, including altered vestibulo-ocular reflexes. |
Xiu-Hong Li; Jin Jing; Xiao-Bing Zou; Xu Huang; Yu Jin; Qing-Xiong Wang; Xue-Bin Chen; Bin-Rang Yang; Si-Yuan Yang Picture perception in Chinese dyslexic children: An eye-movement study Journal Article In: Chinese Medical Journal, vol. 122, no. 3, pp. 267–271, 2009. @article{Li2009, BACKGROUND: Currently, whether or not there is visuospatial impairments in Chinese dyslexic children is still a matter of discussion. The relatively recent application of an eye-tracking paradigm may offer an opportunity to address this issue. In China, in comparison with reading studies, there have not been nearly as many eye movement studies dealing with nonreading tasks such as picture identification and whether Chinese children with dyslexia have a picture processing deficit is not clear. The purposes of the present study were to determine whether or not there is visuospatial impairments in Chinese dyslexic children. Moreover, we attempted to discuss whether or not the abnormal eye movement pattern that dyslexic subjects show during reading of text appropriate for their age is a consequence of their linguistic difficulties. METHODS: An eye-link II High-Speed Eye Tracker was used to track the series of eye-movement of 19 Chinese dyslexic children and 19 Chinese normal children. All of the subjects were presented with three pictures for this eye-tracking task and 6 relative eye-movement parameters, first fixation duration, average fixation duration, average saccade amplitude, mean saccade distance, fixation frequency and saccade frequency were recorded for analysis. RESULTS: Analyzing the relative parameter among three pictures, except for the fixation frequency and the saccade frequency, other eye-movement parameters were significantly different among the three pictures (P<0.05). Among the three pictures, the first fixation duration was longer, and the average fixation duration, the average saccade amplitude and the mean saccade distance were shorter from picture 2 to picture 3. Comparing all eye-movement parameter between the two groups, the scores of average saccade amplitude (P=0.017) and the mean saccade distance (P=0.02) were less in the dyslexia group than in the normal group (P<0.05), other parameters were the same in the two different groups (P>0.05). CONCLUSIONS: The characteristics of the pictures can significantly influence the visuospatial cognitive processing capability of the Chinese children. There is a detectable disability for the Chinese dyslexic children in the visuospatial cognitive processing: their saccade amplitude and mean saccade distance are shorter, which may be interpreted as specific for their reading disability. |
Casimir J. H. Ludwig; Stephen H. Butler; Stéphanie Rossit; Monika Harvey; Iain D. Gilchrist Modelling contralesional movement slowing after unilateral brain damage Journal Article In: Neuroscience Letters, vol. 452, no. 1, pp. 1–4, 2009. @article{Ludwig2009, Effective interaction with the world requires the brain to signal behaviourally relevant events and organise an appropriate and timely motor response to such events. Unilateral brain lesion typically results in a reduction and slowing of motor behaviour directed to contralesional space. Accumulator models of choice and reaction time can distinguish between two possible functional causes of this deficit: slowed extraction of evidence in favour of a motor response or an increase in the required amount of evidence for response generation. Three patients with unilateral damage to the right hemisphere were tested on a visually guided saccade task. All three patients showed a dramatic increase in the latency of their responses to targets in the contralesional visual field. We fit their saccade latency distributions with a number of competing accumulator models that embody the alternative functional causes of this deficit. The latency difference between the two hemifields was best accounted for as an increase in the amount of evidence required for a contralesional response. |
2008 |
Manon W. Jones; Mateo Obregón; M. Louise Kelly; Holly P. Branigan Elucidating the component processes involved in dyslexic and non-dyslexic reading fluency: An eye-tracking study Journal Article In: Cognition, vol. 109, no. 3, pp. 389–407, 2008. @article{Jones2008, The relationship between rapid automatized naming (RAN) and reading fluency is well documented (see Wolf, M. & Bowers, P.G. (1999). The double-deficit hypothesis for the developmental dyslexias. Journal of Educational Psychology, 91(3), 415-438, for a review), but little is known about which component processes are important in RAN, and why developmental dyslexics show longer latencies on these tasks. Researchers disagree as to whether these delays are caused by impaired phonological processing or whether extra-phonological processes also play a role (e.g., Clarke, P., Hulme, C., & Snowling, M. (2005). Individual differences in RAN and reading: A response timing analysis. Journal of Research in Reading, 28(2), 73-86; Wolf, M., Bowers, P.G., & Biddle, K. (2000). Naming-speed processes, timing, and reading: A conceptual review. Journal of learning disabilities, 33(4), 387-407). We conducted an eye-tracking study that manipulated phonological and visual information (as representative of extra-phonological processes) in RAN. Results from linear mixed (LME) effects analyses showed that both phonological and visual processes influence naming-speed for both dyslexic and non-dyslexic groups, but the influence on dyslexic readers is greater. Moreover, dyslexic readers' difficulties in these domains primarily emerge in a measure that explicitly includes the production phase of naming. This study elucidates processes underpinning RAN performance in non-dyslexic readers and pinpoints areas of difficulty for dyslexic readers. We discuss these findings with reference to phonological and extra-phonological hypotheses of naming-speed deficits. |
Chantal Kemner; Lizet Ewijk; Herman Engeland; Ignace T. C. Hooge Brief report: Eye movements during visual search tasks indicate enhanced stimulus discriminability in subjects with PDD Journal Article In: Journal of Autism and Developmental Disorders, vol. 38, no. 3, pp. 553–558, 2008. @article{Kemner2008, Subjects with PDD excel on certain visuo-spatial tasks, amongst which visual search tasks, and this has been attributed to enhanced perceptual discrimination. However, an alternative explanation is that subjects with PDD show a different, more effective search strategy. The present study aimed to test both hypotheses, by measuring eye movements during visual search tasks in high functioning adult men with PDD and a control group. Subjects with PDD were significantly faster than controls in these tasks, replicating earlier findings in children. Eye movement data showed that subjects with PDD made fewer eye movements than controls. No evidence was found for a different search strategy between the groups. The data indicate an enhanced ability to discriminate between stimulus elements in PDD. |
Stefan Klöppel; Bogdan Draganski; Charlotte V. Golding; Carlton Chu; Zoltan Nagy; Philip A. Cook; Stephen L. Hicks; Christopher Kennard; Daniel C. Alexander; Geoff J. M. Parker; Sarah J. Tabrizi; Richard S. J. Frackowiak White matter connections reflect changes in voluntary-guided saccades in pre-symptomatic Huntington's disease Journal Article In: Brain, vol. 131, no. 1, pp. 196–204, 2008. @article{Kloeppel2008, Huntington's disease is caused by a known genetic mutation and so potentially can be diagnosed many years before the onset of symptoms. Neuropathological changes have been found in both striatum and frontal cortex in the pre-symptomatic stage. Disruption of cortico-striatal white matter fibre tracts is therefore likely to contribute to the first clinical signs of the disease. We analysed diffusion tensor MR image (DTI) data from 25 pre-symptomatic gene carriers (PSCs) and 20 matched controls using a multivariate support vector machine to identify patterns of changes in fractional anisotropy (FA). In addition, we performed probabilistic fibre tracking to detect changes in 'streamlines' connecting frontal cortex to striatum. We found a pattern of structural brain changes that includes putamen bilaterally as well as anterior parts of the corpus callosum. This pattern was sufficiently specific to enable us to correctly classify 82% of scans as coming from a PSC or control subject. Fibre tracking revealed a reduction of frontal cortico-fugal streamlines reaching the body of the caudate in PSCs compared to controls. In the left hemispheres of PSCs we found a negative correlation between years to estimated disease onset and streamlines from frontal cortex to body of caudate. A large proportion of the fibres to the caudate body originate from the frontal eye fields, which play an important role in the control of voluntary saccades. This type of saccade is specifically impaired in PSCs and is an early clinical sign of motor abnormalities. A correlation analysis in 14 PSCs revealed that subjects with greater impairment of voluntary-guided saccades had fewer fibre tracking streamlines connecting the frontal cortex and caudate body. Our findings suggest a specific patho-physiological basis for these symptoms by indicating selective vulnerability of the associated white matter tracts. |
Tobias Pflugshaupt; Thomas Nyffeler; Roman Von Wartburg; Christian W. Hess; René M. Müri Loss of exploratory vertical saccades after unilateral frontal eye field damage Journal Article In: Journal of Neurology, Neurosurgery and Psychiatry, vol. 79, no. 4, pp. 474–477, 2008. @article{Pflugshaupt2008, Despite their relevance for locomotion and social interaction in everyday situations, little is known about the cortical control of vertical saccades in humans. Results from microstimulation studies indicate that both frontal eye fields (FEFs) contribute to these eye movements. Here, we present a patient with a damaged right FEF, who hardly made vertical saccades during visual exploration. This finding suggests that, for the cortical control of exploratory vertical saccades, integrity of both FEFs is indeed important. |
Elmar H. Pinkhardt; Reinhart Jürgens; Wolfgang Becker; Federica Valdarno; Albert C. Ludolph; Jan Kassubek Differential diagnostic value of eye movement recording in PSP-parkinsonism, Richardson's syndrome, and idiopathic Parkinson's disease Journal Article In: Journal of Neurology, vol. 255, no. 12, pp. 1916–1925, 2008. @article{Pinkhardt2008, Vertical gaze palsy is a highly relevant clinical sign in parkinsonian syndromes. As the eponymous sign of progressive supranuclear palsy (PSP), it is one of the core features in the diagnosis of this disease. Recent studies have suggested a further differentiation of PSP in Richardson's syndrome (RS) and PSP-parkinsonism (PSPP). The aim of this study was to search for oculomotor abnormalities in the PSP-P subset of a sample of PSP patients and to compare these findings with those of (i) RS patients, (ii) patients with idiopathic Parkinson's disease (IPD), and (iii) a control group. Twelve cases of RS, 5 cases of PSP-P, and 27 cases of IPD were examined by use of video-oculography (VOG) and compared to 23 healthy normal controls. Both groups of PSP patients (RS, PSP-P) had significantly slower saccades than either IPD patients or controls, whereas no differences in saccadic eye peak velocity were found between the two PSP groups or in the comparison of IPD with controls. RS and PSP-P were also similar to each other with regard to smooth pursuit eye movements (SPEM), with both groups having significantly lower gain than controls (except for downward pursuit); however, SPEM gain exhibited no consistent difference between PSP and IPD. A correlation between eye movement data and clinical data (Hoehn & Yahr scale or disease duration) could not be observed. As PSP-P patients were still in an early stage of the disease when a differentiation from IPD is difficult on clinical grounds, the clear-cut separation between PSP-P and IPD obtained by measuring saccade velocity suggests that VOG could contribute to the early differentiation between these patient groups. |
Archana Pradeep; Shery Thomas; Eryl O. Roberts; Frank A. Proudlock; Irene Gottlob Reduction of congenital nystagmus in a patient after smoking cannabis Journal Article In: Strabismus, vol. 16, no. 1, pp. 29–32, 2008. @article{Pradeep2008, INTRODUCTION: Smoking cannabis has been described to reduce acquired pendular nystagmus in MS, but its effect on congenital nystagmus is not known. PURPOSE: To report the effect of smoking cannabis in a case of congenital nystagmus. METHODS: A 19-year-old male with congenital horizontal nystagmus presented to the clinic after smoking 10 mg of cannabis. He claimed that the main reason for smoking cannabis was to improve his vision. At the next clinic appointment, he had not smoked cannabis for 3weeks. Full ophthalmologic examination and eye movement recordings were performed at each visit. RESULTS: Visual acuity improved by 3 logMar lines in the left eye and by 2 logMar lines in the right eye after smoking cannabis. The nystagmus intensities were reduced by 30% in primary position and 44%, 11%, 10% and 40% at 20-degree eccentricity to the right, left, elevation and depression, respectively, after smoking cannabis. CONCLUSION: Cannabis may be beneficial in the treatment of congenital idiopathic nystagmus (CIN). Further research to clarify the safety and efficacy of cannabis in patients with CIN, administered for example by capsules or spray, would be important. |
Z. I. Wang; Louis F. Dell'Osso Tenotomy procedure alleviates the "slow to see" phenomenon in infantile nystagmus syndrome: Model prediction and patient data Journal Article In: Vision Research, vol. 48, no. 12, pp. 1409–1419, 2008. @article{Wang2008, Our purpose was to perform a systematic study of the post-four-muscle-tenotomy procedure changes in target acquisition time by comparing predictions from the behavioral ocular motor system (OMS) model and data from infantile nystagmus syndrome (INS) patients. We studied five INS patients who underwent only tenotomy at the enthesis and reattachment at the original insertion of each (previously unoperated) horizontal rectus muscle for their INS treatment. We measured their pre- and post-tenotomy target acquisition changes using data from infrared reflection and high-speed digital video. Three key aspects were calculated and analyzed: the saccadic latency (Ls), the time to target acquisition after the target jump (Lt) and the normalized stimulus time within the cycle. Analyses were performed in MATLAB environment (The MathWorks, Natick, MA) using OMLAB software (OMtools, available from http://www.omlab.org). Model simulations were performed in MATLAB Simulink environment. The model simulation suggested an Lt reduction due to an overall foveation-quality improvement. Consistent with that prediction, improvement in Lt, ranging from ∼200 ms to ∼500 ms (average ∼ 280 ms), was documented in all five patients post-tenotomy. The Lt improvement was not a result of a reduced Ls. INS patients acquired step-target stimuli faster post-tenotomy. This target acquisition improvement may be due to the elevated foveation quality resulting in less inherent variation in the input to the OMS. A refined behavioral OMS model, with "fast" and "slow" motor neuron pathways and a more physiological plant, successfully predicted this improved visual behavior and again demonstrated its utility in guiding ocular motor research. |
Tamara A. Russell; Melissa J. Green; Ian Simpson; Max Coltheart Remediation of facial emotion perception in schizophrenia: Concomitant changes in visual attention Journal Article In: Schizophrenia Research, vol. 103, no. 1-3, pp. 248–256, 2008. @article{Russell2008, The study examined changes in visual attention in schizophrenia following training with a social-cognitive remediation package designed to improve facial emotion recognition (the Micro-Expression Training Tool; METT). Forty out-patients with schizophrenia were randomly allocated to active training (METT; n = 26), or repeated exposure (RE; n = 14); all completed an emotion recognition task with concurrent eye movement recording. Emotion recognition accuracy was significantly improved in the METT group, and this effect was maintained after one week. Immediately following training, the METT group directed more eye movements within feature areas of faces (i.e., eyes, nose, mouth) compared to the RE group. The number of fixations directed to feature areas of faces was positively associated with emotion recognition accuracy prior to training. After one week, the differences between METT and RE groups in viewing feature areas of faces were reduced to trends. However, within group analyses of the METT group revealed significantly increased number of fixations to, and dwell time within, feature areas following training which were maintained after one week. These results provide the first evidence that improvements in emotion recognition following METT training are associated with changes in visual attention to the feature areas of emotional faces. These findings support the contribution of visual attention abnormalities to emotion recognition impairment in schizophrenia, and suggest that one mechanism for improving emotion recognition involves re-directing visual attention to relevant features of emotional faces. |
Paul Sauleau; Pierre Pollak; Paul Krack; Jean Hubert Courjon; Alain Vighetto; Alim Louis Benabid; Denis Pélisson; Caroline Tilikete Subthalamic stimulation improves orienting gaze movements in Parkinson's disease Journal Article In: Clinical Neurophysiology, vol. 119, no. 8, pp. 1857–1863, 2008. @article{Sauleau2008, Objective: To determine the effect of subthalamic stimulation on visually triggered eye and head movements in patients with Parkinson's disease (PD). Methods: We compared the gain and latency of visually triggered eye and head movements in 12 patients bilaterally implanted into the subthalamic nucleus (STN) for severe PD and six age-matched control subjects. Visually triggered movements of eye (head restrained), and of eye and head (head unrestrained) were recorded in the absence of dopaminergic medication. Bilateral stimulation was turned OFF and then turned ON with voltage and contact used in chronic setting. The latency was determined from the beginning of initial horizontal eye movements relative to the target onset, and the gain was defined as the ratio of the amplitude of the initial movement to the amplitude of the target movement. Results: Without stimulation, the initiation of the head movement was significantly delayed in patients and the gain of head movement was reduced. Our patients also presented significantly prolonged latencies and hypometry of visually triggered saccades in the head-fixed condition and of gaze in head-free condition. Bilateral STN stimulation with therapeutic parameters improved performance of orienting gaze, eye and head movements towards the controls' level. Conclusions: These results demonstrate that visually triggered saccades and orienting eye-head movements are impaired in the advanced stage of PD. In addition, subthalamic stimulation enhances amplitude and shortens latency of these movements. Significance: These results are likely explained by alteration of the information processed by the superior colliculus (SC), a pivotal visuomotor structure involved in both voluntary and reflexive saccades. Improvement of movements with stimulation of the STN may be related to its positive input either on the STN-Substantia Nigra-SC pathway or on the parietal cortex-SC pathway. |
Alexandra Soliman; Gillian A. O'Driscoll; Jens Pruessner; Anne Lise V. Holahan; Isabelle Boileau; Danny Gagnon; Alain Dagher Stress-induced dopamine release in humans at risk of psychosis: A [ "C] raclopride PET study Journal Article In: Neuropsychopharmacology, vol. 33, no. 8, pp. 2033–2041, 2008. @article{Soliman2008, Drugs that increase dopamine levels in the brain can cause psychotic symptoms in healthy individuals and worsen them in schizophrenic patients. Psychological stress also increases dopamine release and is thought to play a role in susceptibility to psychotic illness. We hypothesized that healthy individuals at elevated risk of developing psychosis would show greater striatal dopamine release than controls in response to stress. Using positron emission tomography and [(11)C]raclopride, we measured changes in synaptic dopamine concentrations in 10 controls and 16 psychometric schizotypes; 9 with perceptual aberrations (PerAb, ie positive schizotypy) and 7 with physical anhedonia (PhysAn, ie negative schizotypy). [(11)C]Raclopride binding potential was measured during a psychological stress task and a sensory-motor control. All three groups showed significant increases in self-reported stress and cortisol levels between the stress and control conditions. However, only the PhysAn group showed significant stress-induced dopamine release. Dopamine release in the entire sample was significantly negatively correlated with smooth pursuit gain, an endophenotype linked to frontal lobe function. Our findings suggest the presence of abnormalities in the dopamine response to stress in negative symptom schizotypy, and provide indirect evidence of a link to frontal function. |
Melissa J. Green; Jennifer H. Waldron; Ian Simpson; Max Coltheart Visual processing of social context during mental state perception in schizophrenia Journal Article In: Journal of Psychiatry and Neuroscience, vol. 33, no. 1, pp. 34–42, 2008. @article{Green2008, OBJECTIVE: To examine schizophrenia patients' visual attention to social contextual information during a novel mental state perception task. METHOD: Groups of healthy participants (n = 26) and schizophrenia patients (n = 24) viewed 7 image pairs depicting target characters presented context-free and context-embedded (i.e., within an emotion-congruent social context). Gaze position was recorded with the EyeLink I Gaze Tracker while participants performed a mental state inference task. Mean eye movement variables were calculated for each image series (context-embedded v. context-free) to examine group differences in social context processing. RESULTS: The schizophrenia patients demonstrated significantly fewer saccadic eye movements when viewing context-free images and significantly longer eye-fixation durations when viewing context-embedded images. Healthy individuals significantly shortened eye-fixation durations when viewing context-embedded images, compared with context-free images, to enable rapid scanning and uptake of social contextual information; however, this pattern of visual attention was not pronounced in schizophrenia patients. In association with limited scanning and reduced visual attention to contextual information, schizophrenia patients' assessment of the mental state of characters embedded in social contexts was less accurate. CONCLUSION: In people with schizophrenia, inefficient integration of social contextual information in real-world situations may negatively affect the ability to infer mental and emotional states from facial expressions. |
Giovanni Taibbi; Zhong I. Wang; Louis F. Dell'Osso Infantile nystagmus syndrome : Broadening the high-foveation-quality fi eld with contact lenses Journal Article In: Ophthalmology, vol. 2, no. 3, pp. 585–589, 2008. @article{Taibbi2008, We investigated the effects of contact lenses in broadening and improving the high-foveation-quality fi eld in a subject with infantile nystagmus syndrome (INS). A high-speed, digitized video system was used for the eye-movement recording. The subject was asked to fi xate a far target at different horizontal gaze angles with contact lenses inserted. Data from the subject while fi xating at far without refractive correction and at near (at a convergence angle of 60 PD), were used for comparison. The eXpanded Nystagmus Acuity Function (NAFX) was used to evaluate the foveation quality at each gaze angle. Contact lenses broadened the high- foveation-quality range of gaze angles in this subject. The broadening was comparable to that achieved during 60 PD of convergence although the NAFX values were lower. Contact lenses allowed the subject to see “more” (he had a wider range of high-foveation-quality gaze angles) and “better” (he had improved foveation at each gaze angle). Instead of being contraindicated by INS, contact lenses emerge as a potentially important therapeutic option. Contact lenses employ afferent feedback via the ophthalmic division of the V cranial nerve to damp INS slow phases over a broadened range of gaze angles. This supports the proprioceptive hypothesis of INS improvement. |
Shery Thomas; Frank A. Proudlock; Nagini Sarvananthan; Eryl O. Roberts; Musarat Awan; Rebecca J. McLean; Mylvaganam Surendran; A. S. Anil Kumar; Shegufta J. Farooq; Christopher Degg; Richard P. Gale; Robert D. Reinecke; Geoffrey Woodruff; Andrea Langmann; Susanne Lindner; Sunila Jain; Patrick Tarpey; F. Lucy Raymond; Irene Gottlob Phenotypical characteristics of idiopathic infantile nystagmus with and without mutations in FRMD7 Journal Article In: Brain, vol. 131, no. 5, pp. 1259–1267, 2008. @article{Thomas2008, Idiopathic infantile nystagmus (IIN) consists of involuntary oscillations of the eyes. The familial form is most commonly X-linked. We recently found mutations in a novel gene FRMD7 (Xq26.2), which provided an opportunity to investigate a genetically defined and homogeneous group of patients with nystagmus. We compared clinical features and eye movement recordings of 90 subjects with mutation in the gene (FRMD7 group) to 48 subjects without mutations but with clinical IIN (non-FRMD7 group). Fifty-eight female obligate carriers of the mutation were also investigated. The median visual acuity (VA) was 0.2 logMAR (Snellen equivalent 6/9) in both groups and most patients had good stereopsis. The prevalence of strabismus was also similar (FRMD7: 7.8%, non-FRMD7: 10%). The presence of anomalous head posture (AHP) was significantly higher in the non-FRMD7 group (P < 0.0001). The amplitude of nystagmus was more strongly dependent on the direction of gaze in the FRMD7 group being lower at primary position (P < 0.0001), compared to non-FRMD7 group (P = 0.83). Pendular nystagmus waveforms were also more frequent in the FRMD7 group (P = 0.003). Fifty-three percent of the obligate female carriers of an FRMD7 mutation were clinically affected. The VA's in affected females were slightly better compared to affected males (P = 0.014). Subnormal optokinetic responses were found in a subgroup of obligate unaffected carriers, which may be interpreted as a sub-clinical manifestation. FRMD7 is a major cause of X-linked IIN. Most clinical and eye movement characteristics were similar in the FRMD7 group and non-FRMD7 group with most patients having good VA and stereopsis and low incidence of strabismus. Fewer patients in the FRMD7 group had AHPs, their amplitude of nystagmus being lower in primary position. Our findings are helpful in the clinical identification of IIN and genetic counselling of nystagmus patients. |
Jeremy B. Badler; Philippe Lefèvre; Marcus Missal Anticipatory pursuit is influenced by a concurrent timing task Journal Article In: Journal of Vision, vol. 8, no. 16, pp. 1–9, 2008. @article{Badler2008, The ability to predict upcoming events is important to compensate for relatively long sensory-motor delays. When stimuli are temporally regular, their prediction depends on a representation of elapsed time. However, it is well known that the allocation of attention to the timing of an upcoming event alters this representation. The role of attention on the temporal processing component of prediction was investigated in a visual smooth pursuit task that was performed either in isolation or concurrently with a manual response task. Subjects used smooth pursuit eye movements to accurately track a moving target after a constant-duration delay interval. In the manual response task, subjects had to estimate the instant of target motion onset by pressing a button. The onset of anticipatory pursuit eye movements was used to quantify the subject's estimate of elapsed time. We found that onset times were delayed significantly in the presence of the concurrent manual task relative to the pursuit task in isolation. There was also a correlation between the oculomotor and manual response latencies. In the framework of Scalar Timing Theory, the results are consistent with a centralized attentional gating mechanism that allocates clock resources between smooth pursuit preparation and the parallel timing task. |
Antimo Buonocore; Robert D. McIntosh Saccadic inhibition underlies the remote distractor effect Journal Article In: Experimental Brain Research, vol. 191, no. 1, pp. 117–122, 2008. @article{Buonocore2008, The remote distractor effect is a robust finding whereby a saccade to a lateralised visual target is delayed by the simultaneous, or near simultaneous, onset of a distractor in the opposite hemifield. Saccadic inhibition is a more recently discovered phenomenon whereby a transient change to the scene during a visual task induces a depression in saccadic frequency beginning within 70 ms, and maximal around 90-100 ms. We assessed whether saccadic inhibition is responsible for the increase in saccadic latency induced by remote distractors. Participants performed a simple saccadic task in which the delay between target and distractor was varied between 0, 25, 50, 100 and 150 ms. Examination of the distributions of saccadic latencies showed that each distractor produced a discrete dip in saccadic frequency, time-locked to distractor onset, conforming closely to the character of saccadic inhibition. We conclude that saccadic inhibition underlies the remote distractor effect. |
S. Moshel; Ari Z. Zivotofsky; L. Jin-Rong; Ralf Engbert; Jürgen Kurths; Reinhold Kliegl; Shlomo Havlin Persistence and phase synchronisation properties of fixational eye movements Journal Article In: The European Physical Journal Special Topics, vol. 161, pp. 207–223, 2008. @article{Moshel2008, When we fixate our gaze on a stable object, our eyes move continuously with extremely small involuntary and autonomic movements, that even we are unaware of during their occurrence. One of the roles of these fixational eye movements is to prevent the adaptation of the visual system to continuous illumination and inhibit fading of the image. These random, small movements are restricted at long time scales so as to keep the target at the centre of the field of view. In addition, the synchronisation properties between both eyes are related to binocular coordination in order to provide stereopsis. We investigated the roles of different time scale behaviours, especially how they are expressed in the different spatial directions (vertical versus horizontal). We also tested the synchronisation between both eyes. Results show different scaling behaviour between horizontal and vertical movements. When the small ballistic movements, i.e., microsaccades, are removed, the scaling behaviour in both axes becomes similar. Our findings suggest that microsaccades enhance the persistence at short time scales mostly in the horizontal component and much less in the vertical component. We also applied the phase synchronisation decay method to study the synchronisation between six combinations of binocular fixational eye movement components. We found that the vertical-vertical components of right and left eyes are significantly more synchronised than the horizontal-horizontal components. These differences may be due to the need for continuously moving the eyes in the horizontal plane in order to match the stereoscopic image for different viewing distances. |