Effects of Saccadic Bilateral Eye Movements on Episodic and Semantic Autobiographical Memory Fluency

PubMed Central

Parker, Andrew; Parkin, Adam; Dagnall, Neil

2013-01-01

Performing a sequence of fast saccadic horizontal eye movements has been shown to facilitate performance on a range of cognitive tasks, including the retrieval of episodic memories. One explanation for these effects is based on the hypothesis that saccadic eye movements increase hemispheric interaction, and that such interactions are important for particular types of memory. The aim of the current research was to assess the effect of horizontal saccadic eye movements on the retrieval of both episodic autobiographical memory (event/incident based memory) and semantic autobiographical memory (fact based memory) over recent and more distant time periods. It was found that saccadic eye movements facilitated the retrieval of episodic autobiographical memories (over all time periods) but not semantic autobiographical memories. In addition, eye movements did not enhance the retrieval of non-autobiographical semantic memory. This finding illustrates a dissociation between the episodic and semantic characteristics of personal memory and is considered within the context of hemispheric contributions to episodic memory performance. PMID:24133435

Multipulse control of saccadic eye movements

NASA Technical Reports Server (NTRS)

Lehman, S. L.; Stark, L.

1981-01-01

We present three conclusions regarding the neural control of saccadic eye movements, resulting from comparisons between recorded movements and computer simulations. The controller signal to the muscles is probably a multipulse-step. This kind of signal drives the fastest model trajectories. Finally, multipulse signals explain differences between model and electrophysiological results.

Saccade-related activity in the prefrontal cortex: its role in eye movement control and cognitive functions

PubMed Central

Funahashi, Shintaro

2014-01-01

Prefrontal neurons exhibit saccade-related activity and pre-saccadic memory-related activity often encodes the directions of forthcoming eye movements, in line with demonstrated prefrontal contribution to flexible control of voluntary eye movements. However, many prefrontal neurons exhibit post-saccadic activity that is initiated well after the initiation of eye movement. Although post-saccadic activity has been observed in the frontal eye field, this activity is thought to be a corollary discharge from oculomotor centers, because this activity shows no directional tuning and is observed whenever the monkeys perform eye movements regardless of goal-directed or not. However, prefrontal post-saccadic activities exhibit directional tunings similar as pre-saccadic activities and show context dependency, such that post-saccadic activity is observed only when monkeys perform goal-directed saccades. Context-dependency of prefrontal post-saccadic activity suggests that this activity is not a result of corollary signals from oculomotor centers, but contributes to other functions of the prefrontal cortex. One function might be the termination of memory-related activity after a behavioral response is done. This is supported by the observation that the termination of memory-related activity coincides with the initiation of post-saccadic activity in population analyses of prefrontal activities. The termination of memory-related activity at the end of the trial ensures that the subjects can prepare to receive new and updated information. Another function might be the monitoring of behavioral performance, since the termination of memory-related activity by post-saccadic activity could be associated with informing the correctness of the response and the termination of the trial. However, further studies are needed to examine the characteristics of saccade-related activities in the prefrontal cortex and their functions in eye movement control and a variety of cognitive functions

Saccadic eye movement performance as an indicator of driving ability in elderly drivers.

PubMed

Schmitt, Kai-Uwe; Seeger, Rolf; Fischer, Hartmut; Lanz, Christian; Muser, Markus; Walz, Felix; Schwarz, Urs

2015-01-01

Regular checking of the fitness to drive of elderly car-license holders is required in some countries, and this will become increasingly important as more countries face aging populations. The present study investigated whether the analysis of saccadic eye movements could be used as a screening method for the assessment of driving ability. Three different paradigms (prosaccades, antisaccades, and visuovisual interactive (VVI) saccades) were used to test saccadic eye movements in 144 participants split into four groups: elderly drivers who came to the attention of road authorities for suspected lack of fitness to drive, a group of elderly drivers who served as a comparison group, a group of neurology patients with established brain lesion diagnoses, and a young comparison group. The group of elderly drivers with suspected deficits in driving skills also underwent a medical examination and a practical on-road driving test. The results of the saccadic eye tests of the different groups were compared. Antisaccade results indicated a strong link to driving behaviour: elderly drivers who were not fit to drive exhibited a poor performance on the antisaccade task and the performance in the VVI task was also clearly poorer in this group. Testing saccadic eye movements appears to be a promising and efficient method for screening large numbers of people such as elderly drivers. This study indicated a link between antisaccade performance and the ability to drive. Hence, measuring saccadic eye movements should be considered as a tool for screening the fitness to drive.

Cognitive Control of Saccadic Eye Movements

ERIC Educational Resources Information Center

Hutton, S. B.

2008-01-01

The saccadic eye movement system provides researchers with a powerful tool with which to explore the cognitive control of behaviour. It is a behavioural system whose limited output can be measured with exceptional precision, and whose input can be controlled and manipulated in subtle ways. A range of cognitive processes (notably those involved in…

Relationship between saccadic eye movements and formation of the Krukenberg's spindle-a CFD study.

PubMed

Boushehrian, Hamidreza Hajiani; Abouali, Omid; Jafarpur, Khosrow; Ghaffarieh, Alireza; Ahmadi, Goodarz

2017-09-01

In this research, a series of numerical simulations for evaluating the effects of saccadic eye movement on the aqueous humour (AH) flow field and movement of pigment particles in the anterior chamber (AC) was performed. To predict the flow field of AH in the AC, the unsteady forms of continuity, momentum balance and conservation of energy equations were solved using the dynamic mesh technique for simulating the saccadic motions. Different orientations of the human eye including horizontal, vertical and angles of 10° and 20° were considered. The Lagrangian particle trajectory analysis approach was used to find the trajectories of pigment particles in the eye. Particular attention was given to the relation between the saccadic eye movement and potential formation of Krukenberg's spindle in the eye. The simulation results revealed that the natural convection flow was an effective mechanism for transferring pigment particles from the iris to near the cornea. In addition, the saccadic eye movement was the dominant mechanism for deposition of pigment particles on the cornea, which could lead to the formation of Krukenberg's spindle. The effect of amplitude of saccade motion angle in addition to the orientation of the eye on the formation of Krukenberg's spindle was investigated. © The authors 2016. Published by Oxford University Press on behalf of the Institute of Mathematics and its Applications. All rights reserved.

Saccadic eye movements impose a natural bottleneck on visual short-term memory.

PubMed

Ohl, Sven; Rolfs, Martin

2017-05-01

Visual short-term memory (VSTM) is a crucial repository of information when events unfold rapidly before our eyes, yet it maintains only a fraction of the sensory information encoded by the visual system. Here, we tested the hypothesis that saccadic eye movements provide a natural bottleneck for the transition of fragile content in sensory memory to VSTM. In 4 experiments, we show that saccades, planned and executed after the disappearance of a memory array, markedly bias visual memory performance. First, items that had appeared at the saccade target were more readily remembered than items that had appeared elsewhere, even though the saccade was irrelevant to the memory task (Experiment 1). Second, this influence was strongest for saccades elicited right after the disappearance of the memory array and gradually declined over the course of a second (Experiment 2). Third, the saccade stabilized memory representations: The imposed bias persisted even several seconds after saccade execution (Experiment 3). Finally, the advantage for stimuli congruent with the saccade target occurred even when that stimulus was far less likely to be probed in the memory test than any other stimulus in the array, ruling out a strategic effort of observers to memorize information presented at the saccade target (Experiment 4). Together, these results make a strong case that saccades inadvertently determine the content of VSTM, and highlight the key role of actions for the fundamental building blocks of cognition. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

Development and learning of saccadic eye movements in 7- to 42-month-old children.

PubMed

Alahyane, Nadia; Lemoine-Lardennois, Christelle; Tailhefer, Coline; Collins, Thérèse; Fagard, Jacqueline; Doré-Mazars, Karine

2016-01-01

From birth, infants move their eyes to explore their environment, interact with it, and progressively develop a multitude of motor and cognitive abilities. The characteristics and development of oculomotor control in early childhood remain poorly understood today. Here, we examined reaction time and amplitude of saccadic eye movements in 93 7- to 42-month-old children while they oriented toward visual animated cartoon characters appearing at unpredictable locations on a computer screen over 140 trials. Results revealed that saccade performance is immature in children compared to a group of adults: Saccade reaction times were longer, and saccade amplitude relative to target location (10° eccentricity) was shorter. Results also indicated that performance is flexible in children. Although saccade reaction time decreased as age increased, suggesting developmental improvements in saccade control, saccade amplitude gradually improved over trials. Moreover, similar to adults, children were able to modify saccade amplitude based on the visual error made in the previous trial. This second set of results suggests that short visual experience and/or rapid sensorimotor learning are functional in children and can also affect saccade performance.

Idiosyncratic characteristics of saccadic eye movements when viewing different visual environments.

PubMed

Andrews, T J; Coppola, D M

1999-08-01

Eye position was recorded in different viewing conditions to assess whether the temporal and spatial characteristics of saccadic eye movements in different individuals are idiosyncratic. Our aim was to determine the degree to which oculomotor control is based on endogenous factors. A total of 15 naive subjects viewed five visual environments: (1) The absence of visual stimulation (i.e. a dark room); (2) a repetitive visual environment (i.e. simple textured patterns); (3) a complex natural scene; (4) a visual search task; and (5) reading text. Although differences in visual environment had significant effects on eye movements, idiosyncrasies were also apparent. For example, the mean fixation duration and size of an individual's saccadic eye movements when passively viewing a complex natural scene covaried significantly with those same parameters in the absence of visual stimulation and in a repetitive visual environment. In contrast, an individual's spatio-temporal characteristics of eye movements during active tasks such as reading text or visual search covaried together, but did not correlate with the pattern of eye movements detected when viewing a natural scene, simple patterns or in the dark. These idiosyncratic patterns of eye movements in normal viewing reveal an endogenous influence on oculomotor control. The independent covariance of eye movements during different visual tasks shows that saccadic eye movements during active tasks like reading or visual search differ from those engaged during the passive inspection of visual scenes.

Eye movements evoked by electrical microstimulation of the mesencephalic reticular formation in goldfish.

PubMed

Luque, M A; Pérez-Pérez, M P; Herrero, L; Waitzman, D M; Torres, B

2006-02-01

Anatomical studies in goldfish show that the tectofugal axons provide a large number of boutons within the mesencephalic reticular formation. Electrical stimulation, reversible inactivation and cell recording in the primate central mesencephalic reticular formation have suggested that it participates in the control of rapid eye movements (saccades). Moreover, the role of this tecto-recipient area in the generation of saccadic eye movements in fish is unknown. In this study we show that the electrical microstimulation of the mesencephalic reticular formation of goldfish evoked short latency saccadic eye movements in any direction (contraversive or ipsiversive, upward or downward). Movements of the eyes were usually disjunctive. Based on the location of the sites from which eye movements were evoked and the preferred saccade direction, eye movements were divided into different groups: pure vertical saccades were mainly elicited from the rostral mesencephalic reticular formation, while oblique and pure horizontal were largely evoked from middle and caudal mesencephalic reticular formation zones. The direction and amplitude of pure vertical and horizontal saccades were unaffected by initial eye position. However the amplitude, but not the direction of most oblique saccades was systematically modified by initial eye position. At the same time, the amplitude of elicited saccades did not vary in any consistent manner along either the anteroposterior, dorsoventral or mediolateral axes (i.e. there was no topographic organization of the mesencephalic reticular formation with respect to amplitude). In addition to these groups of movements, we found convergent and goal-directed saccades evoked primarily from the anterior and posterior mesencephalic reticular formation, respectively. Finally, the metric and kinetic characteristics of saccades could be manipulated by changes in the stimulation parameters. We conclude that the mesencephalic reticular formation in goldfish shares

Saccadic eye movements as a measure of residual effects: temazepam compared with other hypnotics.

PubMed

Hofferberth, B; Hirschberg; Grotemeyer

1986-01-01

Eye movements are classified into two categories: quickly running saccades and smooth pursuit movements. Saccades are fast conjugate eye movements with a preprogrammed direction, amplitude, and speed course; their purpose is to register new objects in the visual field. The duration and velocity of saccadic eye movements are very much dependent on vigilance. Comparisons were made with a number of psychometric tests [d 2 Durchstreichtest (cross out test), Viennese determination apparatus, and flicker fusion frequency] and the velocity of fast eye movements. The results of three separate investigations are presented. Standardization was undertaken in 100 healthy volunteers, 50 male and 50 female subjects aged between 20 and more than 50 years were included. In an open parallel group study, comparisons were made between various hypnotics with different half-lives (temazepam, flunitrazepam, flurazepam, and phenobarbital). There were 10 healthy volunteers in each group, and medication was taken as a single night-time dose for 7 nights. In a double-blind study, temazepam (20 mg/day) was tested against flunitrazepam (2 mg/day). Dosing lasted 7 days. A marked impairment of the saccadic eye movements was observed with flunitrazepam but not with temazepam. Of all the benzodiazepines tested, only temazepam had no influence on the parameters of the saccade test. These results can be explained by temazepam's short half-life and also by the fact that no active metabolites are formed.

Differentiation between Vergence and Saccadic Functional Activity within the Human Frontal Eye Fields and Midbrain Revealed through fMRI

PubMed Central

Alkan, Yelda; Biswal, Bharat B.; Alvarez, Tara L.

2011-01-01

Purpose Eye movement research has traditionally studied solely saccade and/or vergence eye movements by isolating these systems within a laboratory setting. While the neural correlates of saccadic eye movements are established, few studies have quantified the functional activity of vergence eye movements using fMRI. This study mapped the neural substrates of vergence eye movements and compared them to saccades to elucidate the spatial commonality and differentiation between these systems. Methodology The stimulus was presented in a block design where the ‘off’ stimulus was a sustained fixation and the ‘on’ stimulus was random vergence or saccadic eye movements. Data were collected with a 3T scanner. A general linear model (GLM) was used in conjunction with cluster size to determine significantly active regions. A paired t-test of the GLM beta weight coefficients was computed between the saccade and vergence functional activities to test the hypothesis that vergence and saccadic stimulation would have spatial differentiation in addition to shared neural substrates. Results Segregated functional activation was observed within the frontal eye fields where a portion of the functional activity from the vergence task was located anterior to the saccadic functional activity (z>2.3; p<0.03). An area within the midbrain was significantly correlated with the experimental design for the vergence but not the saccade data set. Similar functional activation was observed within the following regions of interest: the supplementary eye field, dorsolateral prefrontal cortex, ventral lateral prefrontal cortex, lateral intraparietal area, cuneus, precuneus, anterior and posterior cingulates, and cerebellar vermis. The functional activity from these regions was not different between the vergence and saccade data sets assessed by analyzing the beta weights of the paired t-test (p>0.2). Conclusion Functional MRI can elucidate the differences between the vergence and saccade

Performing saccadic eye movements or blinking improves postural control.

PubMed

Rougier, Patrice; Garin, Mélanie

2007-07-01

To determine the relationship between eye movement and postural control on an undisturbed upright stance maintenance protocol, 15 young, healthy individuals were tested in various conditions. These conditions included imposed blinking patterns and horizontal and vertical saccadic eye movements. The directions taken by the center of pressure (CP) were recorded via a force platform on which the participants remained in an upright position. The CP trajectories were used to estimate, via a low-pass filter, the vertically projected movements of the center of gravity (CGv) and consequently the difference CP-CGv. An analysis of the frequency shows that regular bilateral blinking does not produce a significant change in postural control. In contrast, performing saccadic eye movements induces some reduced amplitude for both basic CGv and CP-CGv movements principally along the antero-posterior axis. The present result supports the theory that some ocular movements may modify postural control in the maintenance of the upright standing position in human participants.

Saccadic eye movements as an index of perceptual decision-making.

PubMed

McSorley, Eugene; McCloy, Rachel

2009-10-01

One of the most common decisions we make is the one about where to move our eyes next. Here we examine the impact that processing the evidence supporting competing options has on saccade programming. Participants were asked to saccade to one of two possible visual targets indicated by a cloud of moving dots. We varied the evidence which supported saccade target choice by manipulating the proportion of dots moving towards one target or the other. The task was found to become easier as the evidence supporting target choice increased. This was reflected in an increase in percent correct and a decrease in saccade latency. The trajectory and landing position of saccades were found to deviate away from the non-selected target reflecting the choice of the target and the inhibition of the non-target. The extent of the deviation was found to increase with amount of sensory evidence supporting target choice. This shows that decision-making processes involved in saccade target choice have an impact on the spatial control of a saccade. This would seem to extend the notion of the processes involved in the control of saccade metrics beyond a competition between visual stimuli to one also reflecting a competition between options.

Inhibition of voluntary saccadic eye movement commands by abrupt visual onsets.

PubMed

Edelman, Jay A; Xu, Kitty Z

2009-03-01

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.

Short-term adaptation of saccades does not affect smooth pursuit eye movement initiation.

PubMed

Sun, Zongpeng; Smilgin, Aleksandra; Junker, Marc; Dicke, Peter W; Thier, Peter

2017-08-01

Scrutiny of the visual environment requires saccades that shift gaze to objects of interest. In case the object should be moving, smooth pursuit eye movements (SPEM) try to keep the image of the object within the confines of the fovea in order to ensure sufficient time for its analysis. Both saccades and SPEM can be adaptively changed by the experience of insufficiencies, compromising the precision of saccades or the minimization of object image slip in the case of SPEM. As both forms of adaptation rely on the cerebellar oculomotor vermis (OMV), most probably deploying a shared neuronal machinery, one might expect that the adaptation of one type of eye movement should affect the kinematics of the other. In order to test this expectation, we subjected two monkeys to a standard saccadic adaption paradigm with SPEM test trials at the end and, alternatively, the same two monkeys plus a third one to a random saccadic adaptation paradigm with interleaved trials of SPEM. In contrast to our expectation, we observed at best marginal transfer which, moreover, had little consistency across experiments and subjects. The lack of consistent transfer of saccadic adaptation decisively constrains models of the implementation of oculomotor learning in the OMV, suggesting an extensive separation of saccade- and SPEM-related synapses on P-cell dendritic trees.

Reduced Misinformation Effects Following Saccadic Bilateral Eye Movements

ERIC Educational Resources Information Center

Parker, Andrew; Buckley, Sharon; Dagnall, Neil

2009-01-01

The effects of saccadic bilateral (horizontal) eye movements on memory for a visual event narrative were investigated. In the study phase, participants were exposed to a set of pictures accompanied by a verbal commentary describing the events depicted in the pictures. Next, the participants were asked either misleading or control questions about…

Voluntary saccadic eye movements in humans studied with a double-cue paradigm.

PubMed

Sheliga, B M; Brown, V J; Miles, F A

2002-07-01

In the classic double-step paradigm, subjects are required to make a saccade to a visual target that is briefly presented at one location and then shifted to a new location before the subject has responded. The saccades in this situation are "reflexive" in that they are made in response to the appearance of the target itself. In the present experiments we adapted the double-step paradigm to study "voluntary" saccades. For this, several identical targets were always visible and subjects were given a cue to indicate that they should make a saccade to one of them. This cue was then changed to indicate another of the targets before the subject had responded: double-cue (DC) paradigm. The saccadic eye movements in our DC paradigm had many features in common with those in the double-step paradigm and we show that apparent differences can be attributed to the spatio-temporal arrangements of the cues/targets rather than to any intrinsic differences in the programming of these two kinds of eye movements. For example, a feature of our DC paradigm that is not seen in the usual double-step paradigm is that the second cue could cause transient delays of the initial saccade, and these delays still occurred when the second cue was reflexive--provided that it was at the fovea (as in our DC paradigm) and not in the periphery (as in the usual double-step paradigm). Thus, the critical factor for the delay was the retinal (foveal) location of the second cue/target--not whether it was cognitive or reflexive--and we argue that the second cue/target is here acting as a distractor. We conclude that the DC paradigm can be used to study the programming of voluntary saccades in the same way that the double-step paradigm can be used to study reflexive saccades.

Saccadic eye movements analysis as a measure of drug effect on central nervous system function.

PubMed

Tedeschi, G; Quattrone, A; Bonavita, V

1986-04-01

Peak velocity (PSV) and duration (SD) of horizontal saccadic eye movements are demonstrably under the control of specific brain stem structures. Experimental and clinical evidence suggest the existence of an immediate premotor system for saccade generation located in the paramedian pontine reticular formation (PPRF). Effects on saccadic eye movements have been studied in normal volunteers with barbiturates, benzodiazepines, amphetamine and ethanol. On two occasions computer analysis of PSV, SD, saccade reaction time (SRT) and saccade accuracy (SA) was carried out in comparison with more traditional methods of assessment of human psychomotor performance like choice reaction time (CRT) and critical flicker fusion threshold (CFFT). The computer system proved to be a highly sensitive and objective method for measuring drug effect on central nervous system (CNS) function. It allows almost continuous sampling of data and appears to be particularly suitable for studying rapidly changing drug effects on the CNS.

Effects of strabismic amblyopia and strabismus without amblyopia on visuomotor behavior, I: saccadic eye movements.

PubMed

Niechwiej-Szwedo, Ewa; Chandrakumar, Manokaraananthan; Goltz, Herbert C; Wong, Agnes M F

2012-11-01

It has previously been shown that anisometropic amblyopia affects the programming and execution of saccades. The aim of the current study was to investigate the impact of strabismic amblyopia on saccade performance. Fourteen adults with strabismic amblyopia, 13 adults with strabismus without amblyopia, and 14 visually normal adults performed saccades and reach-to-touch movements to targets presented at ± 5° and ± 10° eccentricity during binocular and monocular viewing. Latency, amplitude, and peak velocity of primary and secondary saccades were measured. In contrast to visually normal participants who had shorter primary saccade latency during binocular viewing, no binocular advantage was found in patients with strabismus with or without amblyopia. Patients with amblyopia had longer saccade latency during amblyopic eye viewing (P < 0.0001); however, there were no significant differences in saccade amplitude precision among the three groups across viewing conditions. Further analysis showed that only patients with severe amblyopia and no stereopsis (n = 4) exhibited longer latency (which was more pronounced for more central targets; P < 0.0001), and they also had reduced amplitude precision during amblyopic eye viewing. In contrast, patients with mild amblyopia (n = 5) and no stereopsis had normal latency and reduced precision during amblyopic eye viewing (P < 0.001), whereas those with gross stereopsis (n = 5) had normal latency and precision. There were no differences in peak velocity among the groups. Distinct patterns of saccade performance according to different levels of visual acuity and stereoscopic losses in strabismic amblyopia were found. These findings were in contrast to those in anisometropic amblyopia in which the altered saccade performance was independent of the extent of visual acuity or stereoscopic deficits. These results were most likely due to different long-term sensory suppression mechanisms in strabismic versus anisometropic amblyopia.

Competition between color and luminance for target selection in smooth pursuit and saccadic eye movements.

PubMed

Spering, Miriam; Montagnini, Anna; Gegenfurtner, Karl R

2008-11-24

Visual processing of color and luminance for smooth pursuit and saccadic eye movements was investigated using a target selection paradigm. In two experiments, stimuli were varied along the dimensions color and luminance, and selection of the more salient target was compared in pursuit and saccades. Initial pursuit was biased in the direction of the luminance component whereas saccades showed a relative preference for color. An early pursuit response toward luminance was often reversed to color by a later saccade. Observers' perceptual judgments of stimulus salience, obtained in two control experiments, were clearly biased toward luminance. This choice bias in perceptual data implies that the initial short-latency pursuit response agrees with perceptual judgments. In contrast, saccades, which have a longer latency than pursuit, do not seem to follow the perceptual judgment of salience but instead show a stronger relative preference for color. These substantial differences in target selection imply that target selection processes for pursuit and saccadic eye movements use distinctly different weights for color and luminance stimuli.

Visual sensitivity for luminance and chromatic stimuli during the execution of smooth pursuit and saccadic eye movements.

PubMed

Braun, Doris I; Schütz, Alexander C; Gegenfurtner, Karl R

2017-07-01

Visual sensitivity is dynamically modulated by eye movements. During saccadic eye movements, sensitivity is reduced selectively for low-spatial frequency luminance stimuli and largely unaffected for high-spatial frequency luminance and chromatic stimuli (Nature 371 (1994), 511-513). During smooth pursuit eye movements, sensitivity for low-spatial frequency luminance stimuli is moderately reduced while sensitivity for chromatic and high-spatial frequency luminance stimuli is even increased (Nature Neuroscience, 11 (2008), 1211-1216). Since these effects are at least partly of different polarity, we investigated the combined effects of saccades and smooth pursuit on visual sensitivity. For the time course of chromatic sensitivity, we found that detection rates increased slightly around pursuit onset. During saccades to static and moving targets, detection rates dropped briefly before the saccade and reached a minimum at saccade onset. This reduction of chromatic sensitivity was present whenever a saccade was executed and it was not modified by subsequent pursuit. We also measured contrast sensitivity for flashed high- and low-spatial frequency luminance and chromatic stimuli during saccades and pursuit. During saccades, the reduction of contrast sensitivity was strongest for low-spatial frequency luminance stimuli (about 90%). However, a significant reduction was also present for chromatic stimuli (about 58%). Chromatic sensitivity was increased during smooth pursuit (about 12%). These results suggest that the modulation of visual sensitivity during saccades and smooth pursuit is more complex than previously assumed. Copyright © 2017 Elsevier Ltd. All rights reserved.

Topography of eye-position sensitivity of saccades evoked electrically from the cat's superior colliculus.

PubMed

McIlwain, J T

1990-03-01

Saccades evoked electrically from the deep layers of the superior colliculus have been examined in the alert cat with its head fixed. Amplitudes of the vertical and horizontal components varied linearly with the starting position of the eye. The slopes of the linear-regression lines provided an estimate of the sensitivity of these components to initial eye position. In observations on 29 sites in nine cats, the vertical and horizontal components of saccades evoked from a given site were rarely influenced to the same degree by initial eye position. For most sites, the horizontal component was more sensitive than the vertical component. Sensitivities of vertical and horizontal components were lowest near the representations of the horizontal and vertical meridians, respectively, of the collicular retinotopic map, but otherwise exhibited no systematic retinotopic dependence. Estimates of component amplitudes for saccades evoked from the center of the oculomotor range also diverged significantly from those predicted from the retinotopic map. The results of this and previous studies indicate that electrical stimulation of the cat's superior colliculus cannot yield a unique oculomotor map or one that is in register everywhere with the sensory retinotopic map. Several features of these observations suggest that electrical stimulation of the colliculus produces faulty activation of a saccadic control system that computes target position with respect to the head and that small and large saccades are controlled differently.

Geometry and Gesture-Based Features from Saccadic Eye-Movement as a Biometric in Radiology

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hammond, Tracy; Tourassi, Georgia; Yoon, Hong-Jun

In this study, we present a novel application of sketch gesture recognition on eye-movement for biometric identification and estimating task expertise. The study was performed for the task of mammographic screening with simultaneous viewing of four coordinated breast views as typically done in clinical practice. Eye-tracking data and diagnostic decisions collected for 100 mammographic cases (25 normal, 25 benign, 50 malignant) and 10 readers (three board certified radiologists and seven radiology residents), formed the corpus for this study. Sketch gesture recognition techniques were employed to extract geometric and gesture-based features from saccadic eye-movements. Our results show that saccadic eye-movement, characterizedmore » using sketch-based features, result in more accurate models for predicting individual identity and level of expertise than more traditional eye-tracking features.« less

Brain stem omnipause neurons and the control of combined eye-head gaze saccades in the alert cat.

PubMed

Paré, M; Guitton, D

1998-06-01

When the head is unrestrained, rapid displacements of the visual axis-gaze shifts (eye-re-space)-are made by coordinated movements of the eyes (eye-re-head) and head (head-re-space). To address the problem of the neural control of gaze shifts, we studied and contrasted the discharges of omnipause neurons (OPNs) during a variety of combined eye-head gaze shifts and head-fixed eye saccades executed by alert cats. OPNs discharged tonically during intersaccadic intervals and at a reduced level during slow perisaccadic gaze movements sometimes accompanying saccades. Their activity ceased for the duration of the saccadic gaze shifts the animal executed, either by head-fixed eye saccades alone or by combined eye-head movements. This was true for all types of gaze shifts studied: active movements to visual targets; passive movements induced by whole-body rotation or by head rotation about stationary body; and electrically evoked movements by stimulation of the caudal part of the superior colliculus (SC), a central structure for gaze control. For combined eye-head gaze shifts, the OPN pause was therefore not correlated to the eye-in-head trajectory. For instance, in active gaze movements, the end of the pause was better correlated with the gaze end than with either the eye saccade end or the time of eye counterrotation. The hypothesis that cat OPNs participate in controlling gaze shifts is supported by these results, and also by the observation that the movements of both the eyes and the head were transiently interrupted by stimulation of OPNs during gaze shifts. However, we found that the OPN pause could be dissociated from the gaze-motor-error signal producing the gaze shift. First, OPNs resumed discharging when perturbation of head motion briefly interrupted a gaze shift before its intended amplitude was attained. Second, stimulation of caudal SC sites in head-free cat elicited large head-free gaze shifts consistent with the creation of a large gaze-motor-error signal

Target Selection by the Frontal Cortex during Coordinated Saccadic and Smooth Pursuit Eye Movements

ERIC Educational Resources Information Center

Srihasam, Krishna; Bullock, Daniel; Grossberg, Stephen

2009-01-01

Oculomotor tracking of moving objects is an important component of visually based cognition and planning. Such tracking is achieved by a combination of saccades and smooth-pursuit eye movements. In particular, the saccadic and smooth-pursuit systems interact to often choose the same target, and to maximize its visibility through time. How do…

Horizontal Saccadic Eye Movements Enhance the Retrieval of Landmark Shape and Location Information

ERIC Educational Resources Information Center

Brunye, Tad T.; Mahoney, Caroline R.; Augustyn, Jason S.; Taylor, Holly A.

2009-01-01

Recent work has demonstrated that horizontal saccadic eye movements enhance verbal episodic memory retrieval, particularly in strongly right-handed individuals. The present experiments test three primary assumptions derived from this research. First, horizontal eye movements should facilitate episodic memory for both verbal and non-verbal…

Saccadic Eye Movements Impose a Natural Bottleneck on Visual Short-Term Memory

ERIC Educational Resources Information Center

Ohl, Sven; Rolfs, Martin

2017-01-01

Visual short-term memory (VSTM) is a crucial repository of information when events unfold rapidly before our eyes, yet it maintains only a fraction of the sensory information encoded by the visual system. Here, we tested the hypothesis that saccadic eye movements provide a natural bottleneck for the transition of fragile content in sensory memory…

Interaction between Visual- and Goal-Related Neuronal Signals on the Trajectories of Saccadic Eye Movements

ERIC Educational Resources Information Center

White, Brian J.; Theeuwes, Jan; Munoz, Douglas P.

2012-01-01

During natural viewing, the trajectories of saccadic eye movements often deviate dramatically from a straight-line path between objects. In human studies, saccades have been shown to deviate toward or away from salient visual distractors depending on visual- and goal-related parameters, but the neurophysiological basis for this is not well…

SacLab: A toolbox for saccade analysis to increase usability of eye tracking systems in clinical ophthalmology practice.

PubMed

Cercenelli, Laura; Tiberi, Guido; Corazza, Ivan; Giannaccare, Giuseppe; Fresina, Michela; Marcelli, Emanuela

2017-01-01

Many open source software packages have been recently developed to expand the usability of eye tracking systems to study oculomotor behavior, but none of these is specifically designed to encompass all the main functions required for creating eye tracking tests and for providing the automatic analysis of saccadic eye movements. The aim of this study is to introduce SacLab, an intuitive, freely-available MATLAB toolbox based on Graphical User Interfaces (GUIs) that we have developed to increase the usability of the ViewPoint EyeTracker (Arrington Research, Scottsdale, AZ, USA) in clinical ophthalmology practice. SacLab consists of four processing modules that enable the user to easily create visual stimuli tests (Test Designer), record saccadic eye movements (Data Recorder), analyze the recorded data to automatically extract saccadic parameters of clinical interest (Data Analyzer) and provide an aggregate analysis from multiple eye movements recordings (Saccade Analyzer), without requiring any programming effort by the user. A demo application of SacLab to carry out eye tracking tests for the analysis of horizontal saccades was reported. We tested the usability of SacLab toolbox with three ophthalmologists who had no programming experience; the ophthalmologists were briefly trained in the use of SacLab GUIs and were asked to perform the demo application. The toolbox gained an enthusiastic feedback from all the clinicians in terms of intuitiveness, ease of use and flexibility. Test creation and data processing were accomplished in 52±21s and 46±19s, respectively, using the SacLab GUIs. SacLab may represent a useful tool to ease the application of the ViewPoint EyeTracker system in clinical routine in ophthalmology. Copyright © 2016 Elsevier Ltd. All rights reserved.

Bilateral Saccadic Eye Movements and Tactile Stimulation, but Not Auditory Stimulation, Enhance Memory Retrieval

ERIC Educational Resources Information Center

Nieuwenhuis, Sander; Elzinga, Bernet M.; Ras, Priscilla H.; Berends, Floris; Duijs, Peter; Samara, Zoe; Slagter, Heleen A.

2013-01-01

Recent research has shown superior memory retrieval when participants make a series of horizontal saccadic eye movements between the memory encoding phase and the retrieval phase compared to participants who do not move their eyes or move their eyes vertically. It has been hypothesized that the rapidly alternating activation of the two hemispheres…

Novel Eye Movement Disorders in Whipple's Disease-Staircase Horizontal Saccades, Gaze-Evoked Nystagmus, and Esotropia.

PubMed

Shaikh, Aasef G; Ghasia, Fatema F

2017-01-01

Whipple's disease, a rare systemic infectious disorder, is complicated by the involvement of the central nervous system in about 5% of cases. Oscillations of the eyes and the jaw, called oculo-masticatory myorhythmia, are pathognomonic of the central nervous system involvement but are often absent. Typical manifestations of the central nervous system Whipple's disease are cognitive impairment, parkinsonism mimicking progressive supranuclear palsy with vertical saccade slowing, and up-gaze range limitation. We describe a unique patient with the central nervous system Whipple's disease who had typical features, including parkinsonism, cognitive impairment, and up-gaze limitation; but also had diplopia, esotropia with mild horizontal (abduction more than adduction) limitation, and vertigo. The patient also had gaze-evoked nystagmus and staircase horizontal saccades. Latter were thought to be due to mal-programmed small saccades followed by a series of corrective saccades. The saccades were disconjugate due to the concurrent strabismus. Also, we noted disconjugacy in the slow phase of gaze-evoked nystagmus. The disconjugacy of the slow phase of gaze-evoked nystagmus was larger during monocular viewing condition. We propose that interaction of the strabismic drifts of the covered eyes and the nystagmus drift, putatively at the final common pathway might lead to such disconjugacy.

Long-Lasting Modifications of Saccadic Eye Movements Following Adaptation Induced in the Double-Step Target Paradigm

ERIC Educational Resources Information Center

Alahyane, Nadia; Pelisson, Denis

2005-01-01

The adaptation of saccadic eye movements to environmental changes occurring throughout life is a good model of motor learning and motor memory. Numerous studies have analyzed the behavioral properties and neural substrate of oculomotor learning in short-term saccadic adaptation protocols, but to our knowledge, none have tested the persistence of…

Model simulation studies to clarify the effect on saccadic eye movements of initial condition velocities set by the Vestibular Ocular Reflex (VOR)

NASA Technical Reports Server (NTRS)

Nam, M. H.; Winters, J. M.; Stark, L.

1981-01-01

Voluntary active head rotations produced vestibulo-ocular reflex eye movements (VOR) with the subject viewing a fixation target. When this target jumped, the size of the refixation saccades were a function of the ongoing initial velocity of the eye. Saccades made against the VOR were larger in magnitude. Simulation of a reciprocally innervated model eye movement provided results comparable to the experimental data. Most of the experimental effect appeared to be due to linear summation for saccades of 5 and 10 degree magnitude. For small saccades of 2.5 degrees, peripheral nonlinear interaction of state variables in the neuromuscular plant also played a role as proven by comparable behavior in the simulated model with known controller signals.

Face recognition increases during saccade preparation.

PubMed

Lin, Hai; Rizak, Joshua D; Ma, Yuan-ye; Yang, Shang-chuan; Chen, Lin; Hu, Xin-tian

2014-01-01

Face perception is integral to human perception system as it underlies social interactions. Saccadic eye movements are frequently made to bring interesting visual information, such as faces, onto the fovea for detailed processing. Just before eye movement onset, the processing of some basic features, such as the orientation, of an object improves at the saccade landing point. Interestingly, there is also evidence that indicates faces are processed in early visual processing stages similar to basic features. However, it is not known whether this early enhancement of processing includes face recognition. In this study, three experiments were performed to map the timing of face presentation to the beginning of the eye movement in order to evaluate pre-saccadic face recognition. Faces were found to be similarly processed as simple objects immediately prior to saccadic movements. Starting ∼ 120 ms before a saccade to a target face, independent of whether or not the face was surrounded by other faces, the face recognition gradually improved and the critical spacing of the crowding decreased as saccade onset was approaching. These results suggest that an upcoming saccade prepares the visual system for new information about faces at the saccade landing site and may reduce the background in a crowd to target the intended face. This indicates an important role of pre-saccadic eye movement signals in human face recognition.

Adjustment of saccade characteristics during head movements.

NASA Technical Reports Server (NTRS)

Morasso, P.; Bizzi, E.; Dichgans, J.

1973-01-01

Saccade characteristics have been studied during coordinated eye-head movements in monkeys. Amplitude, duration, and peak velocity of saccades with head turning were compared with saccades executed while the head was artificially restrained. The results indicate that the saccade characteristics are modulated as a function of head movement, hence the gaze movement (eye+head) exactly matches saccades with head fixed. Saccade modulation is achieved by way of negative vestibulo-ocular feedback. The neck proprioceptors, because of their longer latency, are effective only if the head starts moving prior to the onset of saccade. It is concluded that saccades make with head turning are not 'ballistic' movements because their trajectory is not entirely predetermined by a central command.

Saccadic foveation of a moving visual target in the rhesus monkey.

PubMed

Fleuriet, Jérome; Hugues, Sandrine; Perrinet, Laurent; Goffart, Laurent

2011-02-01

When generating a saccade toward a moving target, the target displacement that occurs during the period spanning from its detection to the saccade end must be taken into account to accurately foveate the target and to initiate its pursuit. Previous studies have shown that these saccades are characterized by a lower peak velocity and a prolonged deceleration phase. In some cases, a second peak eye velocity appears during the deceleration phase, presumably reflecting the late influence of a mechanism that compensates for the target displacement occurring before saccade end. The goal of this work was to further determine in the head restrained monkey the dynamics of this putative compensatory mechanism. A step-ramp paradigm, where the target motion was orthogonal to a target step occurring along the primary axes, was used to estimate from the generated saccades: a component induced by the target step and another one induced by the target motion. Resulting oblique saccades were compared with saccades to a static target with matched horizontal and vertical amplitudes. This study permitted to estimate the time taken for visual motion-related signals to update the programming and execution of saccades. The amplitude of the motion-related component was slightly hypometric with an undershoot that increased with target speed. Moreover, it matched with the eccentricity that the target had 40-60 ms before saccade end. The lack of significant difference in the delay between the onsets of the horizontal and vertical components between saccades directed toward a static target and those aimed at a moving target questions the late influence of the compensatory mechanism. The results are discussed within the framework of the "dual drive" and "remapping" hypotheses.

Influence of orbital eye position on vertical saccades in progressive supranuclear palsy

PubMed Central

Schneider, Rosalyn; Chen, Athena L.; King, Susan A.; Riley, David E.; Gunzler, Steven A.; Devereaux, Michael. W.; Leigh, R. John

2011-01-01

Disturbance of vertical saccadesis a cardinal feature of progressive supranuclear palsy (PSP). We investigated whether the amplitude and peak velocity of saccades is affected by the orbital position fromwhich movements start in PSP patients and age-matched control subjects. Subjects made vertical saccades in response to ± 5 degree vertical target jumps with their heads in one of three positions: head “center,” head pitched forward ~15 degrees, and head pitched back ~ 15 degrees.All patients showed some effect of starting eye position, whether beginning in the upward or downward field of gaze, on saccade amplitude, peak velocity (PV), and net range of movement. Generally, reduction of amplitude and PV were commensurate and bidirectional in the affected hemifield of gaze. Such findings are unlikelyto be due to orbital factors and could be explained by varying degrees of involvement of rostral midbrain nucleiin the pathological process. PMID:21950977

Visual and auditory cue integration for the generation of saccadic eye movements in monkeys and lever pressing in humans.

PubMed

Schiller, Peter H; Kwak, Michelle C; Slocum, Warren M

2012-08-01

This study examined how effectively visual and auditory cues can be integrated in the brain for the generation of motor responses. The latencies with which saccadic eye movements are produced in humans and monkeys form, under certain conditions, a bimodal distribution, the first mode of which has been termed express saccades. In humans, a much higher percentage of express saccades is generated when both visual and auditory cues are provided compared with the single presentation of these cues [H. C. Hughes et al. (1994) J. Exp. Psychol. Hum. Percept. Perform., 20, 131-153]. In this study, we addressed two questions: first, do monkeys also integrate visual and auditory cues for express saccade generation as do humans and second, does such integration take place in humans when, instead of eye movements, the task is to press levers with fingers? Our results show that (i) in monkeys, as in humans, the combined visual and auditory cues generate a much higher percentage of express saccades than do singly presented cues and (ii) the latencies with which levers are pressed by humans are shorter when both visual and auditory cues are provided compared with the presentation of single cues, but the distribution in all cases is unimodal; response latencies in the express range seen in the execution of saccadic eye movements are not obtained with lever pressing. © 2012 The Authors. European Journal of Neuroscience © 2012 Federation of European Neuroscience Societies and Blackwell Publishing Ltd.

Pharmacology of saccadic eye movements in man. 1. Effects of the benzodiazepine receptor ligands midazolam and flumazenil.

PubMed

Ball, D M; Glue, P; Wilson, S; Nutt, D J

1991-01-01

A paradigm for assessing benzodiazepine receptor sensitivity was developed using intravenous midazolam in normal volunteers. After administration of incremental doses of midazolam, alterations in saccadic eye movement parameters and psychological self ratings were assessed. Significant changes included dose-dependent slowing of peak velocity, peak acceleration, peak deceleration, reduced saccade acceleration/deceleration ratio and saccade accuracy, and increased sedation self-ratings. Changes in saccade variables and sedation ratings were significantly correlated, and also correlated with plasma midazolam concentrations. No significant changes were seen in saccade latency or anxiety self-ratings. Pharmacological specificity of these changes was demonstrated by their reversal with the benzodiazepine antagonist flumazenil. This challenge paradigm appears to be a sensitive means of assessing benzodiazepine receptor function in man.

The cost of making an eye movement: A direct link between visual working memory and saccade execution.

PubMed

Schut, Martijn J; Van der Stoep, Nathan; Postma, Albert; Van der Stigchel, Stefan

2017-06-01

To facilitate visual continuity across eye movements, the visual system must presaccadically acquire information about the future foveal image. Previous studies have indicated that visual working memory (VWM) affects saccade execution. However, the reverse relation, the effect of saccade execution on VWM load is less clear. To investigate the causal link between saccade execution and VWM, we combined a VWM task and a saccade task. Participants were instructed to remember one, two, or three shapes and performed either a No Saccade-, a Single Saccade- or a Dual (corrective) Saccade-task. The results indicate that items stored in VWM are reported less accurately if a single saccade-or a dual saccade-task is performed next to retaining items in VWM. Importantly, the loss of response accuracy for items retained in VWM by performing a saccade was similar to committing an extra item to VWM. In a second experiment, we observed no cost of executing a saccade for auditory working memory performance, indicating that executing a saccade exclusively taxes the VWM system. Our results suggest that the visual system presaccadically stores the upcoming retinal image, which has a similar VWM load as committing one extra item to memory and interferes with stored VWM content. After the saccade, the visual system can retrieve this item from VWM to evaluate saccade accuracy. Our results support the idea that VWM is a system which is directly linked to saccade execution and promotes visual continuity across saccades.

Effects of handedness & saccadic bilateral eye movements on the specificity of past autobiographical memory & episodic future thinking.

PubMed

Parker, Andrew; Parkin, Adam; Dagnall, Neil

2017-06-01

The present research investigated the effects of personal handedness and saccadic eye movements on the specificity of past autobiographical memory and episodic future thinking. Handedness and saccadic eye movements have been hypothesised to share a common functional basis in that both influence cognition through hemispheric interaction. The technique used to elicit autobiographical memory and episodic future thought involved a cued sentence completion procedure that allowed for the production of memories spanning the highly specific to the very general. Experiment 1 found that mixed-handed (vs. right handed) individuals generated more specific past autobiographical memories, but equivalent numbers of specific future predictions. Experiment 2 demonstrated that following 30s of bilateral (horizontal) saccades, more specific cognitions about both the past and future were generated. These findings extend previous research by showing that more distinct and episodic-like information pertaining to the self can be elicited by either mixed-handedness or eye movements. The results are discussed in relation to hemispheric interaction and top-down influences in the control of memory retrieval. Copyright © 2017 Elsevier Inc. All rights reserved.

The relationship between peak velocity of saccadic eye movements and serum benzodiazepine concentration.

PubMed Central

Bittencourt, P R; Wade, P; Smith, A T; Richens, A

1981-01-01

1 Six healthy male volunteers received single oral doses of 10 mg diazepam, 20 mg temazepam, 15 mg flurazepam, 5 mg nitrazepam, 10 mg desmethyl-diazepam and placebo in a double-blind randomized fashion. 2 Peak velocity of saccadic eye movements, serum benzodiazepine concentration, and subjective ratings of wakefulness and co-ordination were measured at intervals up to 12 h after drug administration. 3 All active treatments produced a statistically significant decrease in peak saccadic velocity. The effect of temazepam and diazepam was generally more pronounced than that of flurazepam, nitrazepam and desmethyl-diazepam. 4 There were log-linear correlations between peak saccadic velocity and serum benzodiazepine concentration after ingestion of temazepam, diazepam and nitrazepam. 5 These results demonstrate a clear relationship between serum benzodiazepine concentration and its effect on a convenient measure of brainstem reticular formation function. PMID:6794587

Integrated Bayesian models of learning and decision making for saccadic eye movements.

PubMed

Brodersen, Kay H; Penny, Will D; Harrison, Lee M; Daunizeau, Jean; Ruff, Christian C; Duzel, Emrah; Friston, Karl J; Stephan, Klaas E

2008-11-01

The neurophysiology of eye movements has been studied extensively, and several computational models have been proposed for decision-making processes that underlie the generation of eye movements towards a visual stimulus in a situation of uncertainty. One class of models, known as linear rise-to-threshold models, provides an economical, yet broadly applicable, explanation for the observed variability in the latency between the onset of a peripheral visual target and the saccade towards it. So far, however, these models do not account for the dynamics of learning across a sequence of stimuli, and they do not apply to situations in which subjects are exposed to events with conditional probabilities. In this methodological paper, we extend the class of linear rise-to-threshold models to address these limitations. Specifically, we reformulate previous models in terms of a generative, hierarchical model, by combining two separate sub-models that account for the interplay between learning of target locations across trials and the decision-making process within trials. We derive a maximum-likelihood scheme for parameter estimation as well as model comparison on the basis of log likelihood ratios. The utility of the integrated model is demonstrated by applying it to empirical saccade data acquired from three healthy subjects. Model comparison is used (i) to show that eye movements do not only reflect marginal but also conditional probabilities of target locations, and (ii) to reveal subject-specific learning profiles over trials. These individual learning profiles are sufficiently distinct that test samples can be successfully mapped onto the correct subject by a naïve Bayes classifier. Altogether, our approach extends the class of linear rise-to-threshold models of saccadic decision making, overcomes some of their previous limitations, and enables statistical inference both about learning of target locations across trials and the decision-making process within trials.

Salient Distractors Can Induce Saccade Adaptation

PubMed Central

Khan, Afsheen; McFadden, Sally A.; Wallman, Josh

2014-01-01

When saccadic eye movements consistently fail to land on their intended target, saccade accuracy is maintained by gradually adapting the movement size of successive saccades. The proposed error signal for saccade adaptation has been based on the distance between where the eye lands and the visual target (retinal error). We studied whether the error signal could alternatively be based on the distance between the predicted and actual locus of attention after the saccade. Unlike conventional adaptation experiments that surreptitiously displace the target once a saccade is initiated towards it, we instead attempted to draw attention away from the target by briefly presenting salient distractor images on one side of the target after the saccade. To test whether less salient, more predictable distractors would induce less adaptation, we separately used fixed random noise distractors. We found that both visual attention distractors were able to induce a small degree of downward saccade adaptation but significantly more to the more salient distractors. As in conventional adaptation experiments, upward adaptation was less effective and salient distractors did not significantly increase amplitudes. We conclude that the locus of attention after the saccade can act as an error signal for saccade adaptation. PMID:24876947

Effects of Handedness and Saccadic Bilateral Eye Movements on Components of Autobiographical Recollection

ERIC Educational Resources Information Center

Parker, Andrew; Dagnall, Neil

2010-01-01

The effects of handedness and saccadic bilateral eye movements on autobiographical recollection were investigated. Recall of autobiographical memories was cued by the use of neutral and emotional words. Autobiographical recollection was assessed by the autobiographical memory questionnaire. Experiment 1 found that mixed-handed (vs. right handed)…

Neural control of visual search by frontal eye field: effects of unexpected target displacement on visual selection and saccade preparation.

PubMed

Murthy, Aditya; Ray, Supriya; Shorter, Stephanie M; Schall, Jeffrey D; Thompson, Kirk G

2009-05-01

The dynamics of visual selection and saccade preparation by the frontal eye field was investigated in macaque monkeys performing a search-step task combining the classic double-step saccade task with visual search. Reward was earned for producing a saccade to a color singleton. On random trials the target and one distractor swapped locations before the saccade and monkeys were rewarded for shifting gaze to the new singleton location. A race model accounts for the probabilities and latencies of saccades to the initial and final singleton locations and provides a measure of the duration of a covert compensation process-target-step reaction time. When the target stepped out of a movement field, noncompensated saccades to the original location were produced when movement-related activity grew rapidly to a threshold. Compensated saccades to the final location were produced when the growth of the original movement-related activity was interrupted within target-step reaction time and was replaced by activation of other neurons producing the compensated saccade. When the target stepped into a receptive field, visual neurons selected the new target location regardless of the monkeys' response. When the target stepped out of a receptive field most visual neurons maintained the representation of the original target location, but a minority of visual neurons showed reduced activity. Chronometric analyses of the neural responses to the target step revealed that the modulation of visually responsive neurons and movement-related neurons occurred early enough to shift attention and saccade preparation from the old to the new target location. These findings indicate that visual activity in the frontal eye field signals the location of targets for orienting, whereas movement-related activity instantiates saccade preparation.

Pre-saccadic perception: Separate time courses for enhancement and spatial pooling at the saccade target

PubMed Central

Buonocore, Antimo; Fracasso, Alessio; Melcher, David

2017-01-01

We interact with complex scenes using eye movements to select targets of interest. Studies have shown that the future target of a saccadic eye movement is processed differently by the visual system. A number of effects have been reported, including a benefit for perceptual performance at the target (“enhancement”), reduced influences of backward masking (“un-masking”), reduced crowding (“un-crowding”) and spatial compression towards the saccade target. We investigated the time course of these effects by measuring orientation discrimination for targets that were spatially crowded or temporally masked. In four experiments, we varied the target-flanker distance, the presence of forward/backward masks, the orientation of the flankers and whether participants made a saccade. Masking and randomizing flanker orientation reduced performance in both fixation and saccade trials. We found a small improvement in performance on saccade trials, compared to fixation trials, with a time course that was consistent with a general enhancement at the saccade target. In addition, a decrement in performance (reporting the average flanker orientation, rather than the target) was found in the time bins nearest saccade onset when random oriented flankers were used, consistent with spatial pooling around the saccade target. We did not find strong evidence for un-crowding. Overall, our pattern of results was consistent with both an early, general enhancement at the saccade target and a later, peri-saccadic compression/pooling towards the saccade target. PMID:28614367

What do eye movements tell us about patients with neurological disorders? — An introduction to saccade recording in the clinical setting —

PubMed Central

TERAO, Yasuo; FUKUDA, Hideki; HIKOSAKA, Okihide

2017-01-01

Non-invasive and readily implemented in the clinical setting, eye movement studies have been conducted extensively not only in healthy human subjects but also in patients with neurological disorders. The purpose of saccade studies is to “read out” the pathophysiology underlying neurological disorders from the saccade records, referring to known primate physiology. In the current review, we provide an overview of studies in which we attempted to elucidate the patterns of saccade abnormalities in over 250 patients with neurological disorders, including cerebellar ataxia and brainstem pathology due to neurodegenerative disorders, and what they tell about the pathophysiology of patients with neurological disorders. We also discuss how interventions, such as deep brain stimulation, affect saccade performance and provide further insights into the workings of the oculomotor system in humans. Finally, we argue that it is important to understand the functional significance and behavioral correlate of saccade abnormalities in daily life, which could require eye tracking methodologies to be performed in settings similar to daily life. PMID:29225306

Reverse design of a bull's eye structure for oblique incidence and wider angular transmission efficiency.

PubMed

Yamada, Akira; Terakawa, Mitsuhiro

2015-04-10

We present a design method of a bull's eye structure with asymmetric grooves for focusing oblique incident light. The design method is capable of designing transmission peaks to a desired oblique angle with capability of collecting light from a wider range of angles. The bull's eye groove geometry for oblique incidence is designed based on the electric field intensity pattern around an isolated subwavelength aperture on a thin gold film at oblique incidence, calculated by the finite difference time domain method. Wide angular transmission efficiency is successfully achieved by overlapping two different bull's eye groove patterns designed with different peak angles. Our novel design method would overcome the angular limitations of the conventional methods.

Responses of Purkinje cells in the oculomotor vermis of monkeys during smooth pursuit eye movements and saccades: comparison with floccular complex.

PubMed

Raghavan, Ramanujan T; Lisberger, Stephen G

2017-08-01

We recorded the responses of Purkinje cells in the oculomotor vermis during smooth pursuit and saccadic eye movements. Our goal was to characterize the responses in the vermis using approaches that would allow direct comparisons with responses of Purkinje cells in another cerebellar area for pursuit, the floccular complex. Simple-spike firing of vermis Purkinje cells is direction selective during both pursuit and saccades, but the preferred directions are sufficiently independent so that downstream circuits could decode signals to drive pursuit and saccades separately. Complex spikes also were direction selective during pursuit, and almost all Purkinje cells showed a peak in the probability of complex spikes during the initiation of pursuit in at least one direction. Unlike the floccular complex, the preferred directions for simple spikes and complex spikes were not opposite. The kinematics of smooth eye movement described the simple-spike responses of vermis Purkinje cells well. Sensitivities were similar to those in the floccular complex for eye position and considerably lower for eye velocity and acceleration. The kinematic relations were quite different for saccades vs. pursuit, supporting the idea that the contributions from the vermis to each kind of movement could contribute independently in downstream areas. Finally, neither the complex-spike nor the simple-spike responses of vermis Purkinje cells were appropriate to support direction learning in pursuit. Complex spikes were not triggered reliably by an instructive change in target direction; simple-spike responses showed very small amounts of learning. We conclude that the vermis plays a different role in pursuit eye movements compared with the floccular complex. NEW & NOTEWORTHY The midline oculomotor cerebellum plays a different role in smooth pursuit eye movements compared with the lateral, floccular complex and appears to be much less involved in direction learning in pursuit. The output from the

Dynamic coding of vertical facilitated vergence by premotor saccadic burst neurons.

PubMed

Van Horn, Marion R; Cullen, Kathleen E

2008-10-01

To redirect our gaze in three-dimensional space we frequently combine saccades and vergence. These eye movements, known as disconjugate saccades, are characterized by eyes rotating by different amounts, with markedly different dynamics, and occur whenever gaze is shifted between near and far objects. How the brain ensures the precise control of binocular positioning remains controversial. It has been proposed that the traditionally assumed "conjugate" saccadic premotor pathway does not encode conjugate commands but rather encodes monocular commands for the right or left eye during saccades. Here, we directly test this proposal by recording from the premotor neurons of the horizontal saccade generator during a dissociation task that required a vergence but no horizontal conjugate saccadic command. Specifically, saccadic burst neurons (SBNs) in the paramedian pontine reticular formation were recorded while rhesus monkeys made vertical saccades made between near and far targets. During this task, we first show that peak vergence velocities were enhanced to saccade-like speeds (e.g., >150 vs. <100 degrees/s during saccade-free movements for comparable changes in vergence angle). We then quantified the discharge dynamics of SBNs during these movements and found that the majority of the neurons preferentially encode the velocity of the ipsilateral eye. Notably, a given neuron typically encoded the movement of the same eye during horizontal saccades that were made in depth. Taken together, our findings demonstrate that the brain stem saccadic burst generator encodes integrated conjugate and vergence commands, thus providing strong evidence for the proposal that the classic saccadic premotor pathway controls gaze in three-dimensional space.

The kinematics of far-near re-fixation saccades

PubMed Central

Misslisch, H.

2015-01-01

We have analyzed the three-dimensional spatiotemporal characteristics of saccadic refixations between far and near targets in three behaviorally trained rhesus monkeys. The kinematics underlying these rapid eye movements can be accurately described by rotations of the eyes in four different planes, namely, first disconjugate rotations in the horizontal plane of regard converging the eyes toward the near target, followed by rotations in each eye's vertical direction plane, and finally, disconjugate rotations in a common frontoparallel plane. This compounded rotation of the eye was underlying an initially fast-rising variable torsion that typically overshot the final torsion, which the eyes attained at the time of target acquisition. The torsion consisted of a coarse, widely varying component of opposite polarity in the two eyes, which contained a more robust, much smaller modulation that sharply increased toward the end of saccades. The reorientation of the eyes in torsion depended on each eye's azimuth, elevation, and target distance. We conclude that refixation saccades are generated by motor commands that control ocular torsion in concert with the saccade generator, which operates in Donders-Listing kinematics underlying Listing's law. PMID:25717167

Figure-ground activity in V1 and guidance of saccadic eye movements.

PubMed

Supèr, Hans

2006-01-01

Every day we shift our gaze about 150.000 times mostly without noticing it. The direction of these gaze shifts are not random but directed by sensory information and internal factors. After each movement the eyes hold still for a brief moment so that visual information at the center of our gaze can be processed in detail. This means that visual information at the saccade target location is sufficient to accurately guide the gaze shift but yet is not sufficiently processed to be fully perceived. In this paper I will discuss the possible role of activity in the primary visual cortex (V1), in particular figure-ground activity, in oculo-motor behavior. Figure-ground activity occurs during the late response period of V1 neurons and correlates with perception. The strength of figure-ground responses predicts the direction and moment of saccadic eye movements. The superior colliculus, a gaze control center that integrates visual and motor signals, receives direct anatomical connections from V1. These projections may convey the perceptual information that is required for appropriate gaze shifts. In conclusion, figure-ground activity in V1 may act as an intermediate component linking visual and motor signals.

Error correcting mechanisms during antisaccades: contribution of online control during primary saccades and offline control via secondary saccades.

PubMed

Bedi, Harleen; Goltz, Herbert C; Wong, Agnes M F; Chandrakumar, Manokaraananthan; Niechwiej-Szwedo, Ewa

2013-01-01

Errors in eye movements can be corrected during the ongoing saccade through in-flight modifications (i.e., online control), or by programming a secondary eye movement (i.e., offline control). In a reflexive saccade task, the oculomotor system can use extraretinal information (i.e., efference copy) online to correct errors in the primary saccade, and offline retinal information to generate a secondary corrective saccade. The purpose of this study was to examine the error correction mechanisms in the antisaccade task. The roles of extraretinal and retinal feedback in maintaining eye movement accuracy were investigated by presenting visual feedback at the spatial goal of the antisaccade. We found that online control for antisaccade is not affected by the presence of visual feedback; that is whether visual feedback is present or not, the duration of the deceleration interval was extended and significantly correlated with reduced antisaccade endpoint error. We postulate that the extended duration of deceleration is a feature of online control during volitional saccades to improve their endpoint accuracy. We found that secondary saccades were generated more frequently in the antisaccade task compared to the reflexive saccade task. Furthermore, we found evidence for a greater contribution from extraretinal sources of feedback in programming the secondary "corrective" saccades in the antisaccade task. Nonetheless, secondary saccades were more corrective for the remaining antisaccade amplitude error in the presence of visual feedback of the target. Taken together, our results reveal a distinctive online error control strategy through an extension of the deceleration interval in the antisaccade task. Target feedback does not improve online control, rather it improves the accuracy of secondary saccades in the antisaccade task.

Error Correcting Mechanisms during Antisaccades: Contribution of Online Control during Primary Saccades and Offline Control via Secondary Saccades

PubMed Central

Bedi, Harleen; Goltz, Herbert C.; Wong, Agnes M. F.; Chandrakumar, Manokaraananthan; Niechwiej-Szwedo, Ewa

2013-01-01

Errors in eye movements can be corrected during the ongoing saccade through in-flight modifications (i.e., online control), or by programming a secondary eye movement (i.e., offline control). In a reflexive saccade task, the oculomotor system can use extraretinal information (i.e., efference copy) online to correct errors in the primary saccade, and offline retinal information to generate a secondary corrective saccade. The purpose of this study was to examine the error correction mechanisms in the antisaccade task. The roles of extraretinal and retinal feedback in maintaining eye movement accuracy were investigated by presenting visual feedback at the spatial goal of the antisaccade. We found that online control for antisaccade is not affected by the presence of visual feedback; that is whether visual feedback is present or not, the duration of the deceleration interval was extended and significantly correlated with reduced antisaccade endpoint error. We postulate that the extended duration of deceleration is a feature of online control during volitional saccades to improve their endpoint accuracy. We found that secondary saccades were generated more frequently in the antisaccade task compared to the reflexive saccade task. Furthermore, we found evidence for a greater contribution from extraretinal sources of feedback in programming the secondary “corrective” saccades in the antisaccade task. Nonetheless, secondary saccades were more corrective for the remaining antisaccade amplitude error in the presence of visual feedback of the target. Taken together, our results reveal a distinctive online error control strategy through an extension of the deceleration interval in the antisaccade task. Target feedback does not improve online control, rather it improves the accuracy of secondary saccades in the antisaccade task. PMID:23936308

Implications of Lateral Cerebellum in Proactive Control of Saccades.

PubMed

Kunimatsu, Jun; Suzuki, Tomoki W; Tanaka, Masaki

2016-06-29

Although several lines of evidence establish the involvement of the medial and vestibular parts of the cerebellum in the adaptive control of eye movements, the role of the lateral hemisphere of the cerebellum in eye movements remains unclear. Ascending projections from the lateral cerebellum to the frontal and parietal association cortices via the thalamus are consistent with a role of these pathways in higher-order oculomotor control. In support of this, previous functional imaging studies and recent analyses in subjects with cerebellar lesions have indicated a role for the lateral cerebellum in volitional eye movements such as anti-saccades. To elucidate the underlying mechanisms, we recorded from single neurons in the dentate nucleus of the cerebellum in monkeys performing anti-saccade/pro-saccade tasks. We found that neurons in the posterior part of the dentate nucleus showed higher firing rates during the preparation of anti-saccades compared with pro-saccades. When the animals made erroneous saccades to the visual stimuli in the anti-saccade trials, the firing rate during the preparatory period decreased. Furthermore, local inactivation of the recording sites with muscimol moderately increased the proportion of error trials, while successful anti-saccades were more variable and often had shorter latency during inactivation. Thus, our results show that neuronal activity in the cerebellar dentate nucleus causally regulates anti-saccade performance. Neuronal signals from the lateral cerebellum to the frontal cortex might modulate the proactive control signals in the corticobasal ganglia circuitry that inhibit early reactive responses and possibly optimize the speed and accuracy of anti-saccades. Although the lateral cerebellum is interconnected with the cortical eye fields via the thalamus and the pons, its role in eye movements remains unclear. We found that neurons in the caudal part of the lateral (dentate) nucleus of the cerebellum showed the increased

Efficient Saccade Planning Requires Time and Clear Choices

PubMed Central

Ghahghaei, Saiedeh; Verghese, Preeti

2015-01-01

We use eye movements constantly to gather information. Saccades are efficient when they maximize the information required for the task, however there is controversy regarding the efficiency of eye movement planning. For example, saccades are efficient when searching for a single target (Nature, 434 (2005) 387–91), but are inefficient when searching for an unknown number of targets in noise, particularly under time pressure (Vision Research 74 (2012), 61–71). In this study, we used a multiple-target search paradigm and explored whether altering the noise level or increasing saccadic latency improved efficiency. Experiments used stimuli with two levels of discriminability such that saccades to the less discriminable stimuli provided more information. When these two noise levels corresponded to low and moderate visibility, most observers did not preferentially select informative locations, but looked at uncertain and probable target locations equally often. We then examined whether eye movements could be made more efficient by increasing the discriminability of the two stimulus levels and by delaying the first saccade so that there was more time for decision processes to influence the saccade choices. Some observers did indeed increase the proportion of their saccades to informative locations under these conditions. Others, however, made as many saccades as they could during the limited time and were unselective about the saccade goal. A clear trend that emerges across all experiments is that conditions with a greater proportion of efficient saccades are associated with a longer latency to initiate saccades, suggesting that the choice of informative locations requires deliberate planning. PMID:26037735

Effects of long and short simulated flights on the saccadic eye movement velocity of aviators.

PubMed

Di Stasi, Leandro L; McCamy, Michael B; Martinez-Conde, Susana; Gayles, Ellis; Hoare, Chad; Foster, Michael; Catena, Andrés; Macknik, Stephen L

2016-01-01

Aircrew fatigue is a major contributor to operational errors in civil and military aviation. Objective detection of pilot fatigue is thus critical to prevent aviation catastrophes. Previous work has linked fatigue to changes in oculomotor dynamics, but few studies have studied this relationship in critical safety environments. Here we measured the eye movements of US Marine Corps combat helicopter pilots before and after simulated flight missions of different durations.We found a decrease in saccadic velocities after long simulated flights compared to short simulated flights. These results suggest that saccadic velocity could serve as a biomarker of aviator fatigue.

Rapid Simultaneous Enhancement of Visual Sensitivity and Perceived Contrast during Saccade Preparation

PubMed Central

Rolfs, Martin; Carrasco, Marisa

2012-01-01

Humans and other animals with foveate vision make saccadic eye movements to prioritize the visual analysis of behaviorally relevant information. Even before movement onset, visual processing is selectively enhanced at the target of a saccade, presumably gated by brain areas controlling eye movements. Here we assess concurrent changes in visual performance and perceived contrast before saccades, and show that saccade preparation enhances perception rapidly, altering early visual processing in a manner akin to increasing the physical contrast of the visual input. Observers compared orientation and contrast of a test stimulus, appearing briefly before a saccade, to a standard stimulus, presented previously during a fixation period. We found simultaneous progressive enhancement in both orientation discrimination performance and perceived contrast as time approached saccade onset. These effects were robust as early as 60 ms after the eye movement was cued, much faster than the voluntary deployment of covert attention (without eye movements), which takes ~300 ms. Our results link the dynamics of saccade preparation, visual performance, and subjective experience and show that upcoming eye movements alter visual processing by increasing the signal strength. PMID:23035086

What triggers catch-up saccades during visual tracking?

PubMed

de Brouwer, Sophie; Yuksel, Demet; Blohm, Gunnar; Missal, Marcus; Lefèvre, Philippe

2002-03-01

When tracking moving visual stimuli, primates orient their visual axis by combining two kinds of eye movements, smooth pursuit and saccades, that have very different dynamics. Yet, the mechanisms that govern the decision to switch from one type of eye movement to the other are still poorly understood, even though they could bring a significant contribution to the understanding of how the CNS combines different kinds of control strategies to achieve a common motor and sensory goal. In this study, we investigated the oculomotor responses to a large range of different combinations of position error and velocity error during visual tracking of moving stimuli in humans. We found that the oculomotor system uses a prediction of the time at which the eye trajectory will cross the target, defined as the "eye crossing time" (T(XE)). The eye crossing time, which depends on both position error and velocity error, is the criterion used to switch between smooth and saccadic pursuit, i.e., to trigger catch-up saccades. On average, for T(XE) between 40 and 180 ms, no saccade is triggered and target tracking remains purely smooth. Conversely, when T(XE) becomes smaller than 40 ms or larger than 180 ms, a saccade is triggered after a short latency (around 125 ms).

Selective enhancement of orientation tuning before saccades.

PubMed

Ohl, Sven; Kuper, Clara; Rolfs, Martin

2017-11-01

Saccadic eye movements cause a rapid sweep of the visual image across the retina and bring the saccade's target into high-acuity foveal vision. Even before saccade onset, visual processing is selectively prioritized at the saccade target. To determine how this presaccadic attention shift exerts its influence on visual selection, we compare the dynamics of perceptual tuning curves before movement onset at the saccade target and in the opposite hemifield. Participants monitored a 30-Hz sequence of randomly oriented gratings for a target orientation. Combining a reverse correlation technique previously used to study orientation tuning in neurons and general additive mixed modeling, we found that perceptual reports were tuned to the target orientation. The gain of orientation tuning increased markedly within the last 100 ms before saccade onset. In addition, we observed finer orientation tuning right before saccade onset. This increase in gain and tuning occurred at the saccade target location and was not observed at the incongruent location in the opposite hemifield. The present findings suggest, therefore, that presaccadic attention exerts its influence on vision in a spatially and feature-selective manner, enhancing performance and sharpening feature tuning at the future gaze location before the eyes start moving.

The Role of Predictability in Saccadic Eye Responses in the Suppression Head Impulse Test of Horizontal Semicircular Canal Function.

PubMed

Rey-Martinez, Jorge; Yanes, Joaquin; Esteban, Jonathan; Sanz, Ricardo; Martin-Sanz, Eduardo

2017-01-01

In the suppression head impulse paradigm (SHIMP) vHIT protocol, the participant is instructed to follow with his gaze a mobile target generated by a laser placed on the participant's head. Recent studies have reported that the refixation saccade latencies are in relation with the time evolution of the vestibular dysfunction in both (standard and SHIMP) procedures. We hypothesized that some central mechanisms like head impulse prediction could be one of the causes for the differences in the saccadic eye responses. A prospective cohort non-randomized study was designed. For the SHIMP protocol, recorded with the ICS Impulse ver. 4.0 ® (Otometrics A/S, Taastrup, Denmark) vHIT device, three different algorithms were performed: "predictable," "less predictable," and "unpredictable" depending on the target's predictability. A mathematical method was developed to analyze the SHIMP responses. The method was implemented as an additional tool to the MATLAB open source script for the extended analysis of the vHIT responses named HITCal. In cohort 1, 52 participants were included in "predictable" SHIMP protocol. In cohort 2, 60 patients were included for the "less predictable" and 35 patients for the "unpredictable" SHIMP protocol. The participants made more early saccades when instructed to perform the "predictable" paradigm compared with the "less predictable" paradigm ( p  < 0.001). The less predictable protocol did not reveal any significant difference when compared with the unpredictable protocol ( p  = 0.189). For the latency of the first saccade, there was statistical difference between the "unpredictable" and "predictable" protocols ( p  < 0.001) and between the "less predictable" and "predictable" protocols ( p  < 0.001). Finally, we did not find any relationship between the horizontal vestibulo-ocular reflex (hVOR) gain and the latency of the saccades. We developed a specific method to analyze and detect early SHIMP saccades. Our findings offer

Saccadic Corollary Discharge Underlies Stable Visual Perception

PubMed Central

Berman, Rebecca A.; Joiner, Wilsaan M.; Wurtz, Robert H.

2016-01-01

Saccadic eye movements direct the high-resolution foveae of our retinas toward objects of interest. With each saccade, the image jumps on the retina, causing a discontinuity in visual input. Our visual perception, however, remains stable. Philosophers and scientists over centuries have proposed that visual stability depends upon an internal neuronal signal that is a copy of the neuronal signal driving the eye movement, now referred to as a corollary discharge (CD) or efference copy. In the old world monkey, such a CD circuit for saccades has been identified extending from superior colliculus through MD thalamus to frontal cortex, but there is little evidence that this circuit actually contributes to visual perception. We tested the influence of this CD circuit on visual perception by first training macaque monkeys to report their perceived eye direction, and then reversibly inactivating the CD as it passes through the thalamus. We found that the monkey's perception changed; during CD inactivation, there was a difference between where the monkey perceived its eyes to be directed and where they were actually directed. Perception and saccade were decoupled. We established that the perceived eye direction at the end of the saccade was not derived from proprioceptive input from eye muscles, and was not altered by contextual visual information. We conclude that the CD provides internal information contributing to the brain's creation of perceived visual stability. More specifically, the CD might provide the internal saccade vector used to unite separate retinal images into a stable visual scene. SIGNIFICANCE STATEMENT Visual stability is one of the most remarkable aspects of human vision. The eyes move rapidly several times per second, displacing the retinal image each time. The brain compensates for this disruption, keeping our visual perception stable. A major hypothesis explaining this stability invokes a signal within the brain, a corollary discharge, that informs

The brain stem saccadic burst generator encodes gaze in three-dimensional space.

PubMed

Van Horn, Marion R; Sylvestre, Pierre A; Cullen, Kathleen E

2008-05-01

When we look between objects located at different depths the horizontal movement of each eye is different from that of the other, yet temporally synchronized. Traditionally, a vergence-specific neuronal subsystem, independent from other oculomotor subsystems, has been thought to generate all eye movements in depth. However, recent studies have challenged this view by unmasking interactions between vergence and saccadic eye movements during disconjugate saccades. Here, we combined experimental and modeling approaches to address whether the premotor command to generate disconjugate saccades originates exclusively in "vergence centers." We found that the brain stem burst generator, which is commonly assumed to drive only the conjugate component of eye movements, carries substantial vergence-related information during disconjugate saccades. Notably, facilitated vergence velocities during disconjugate saccades were synchronized with the burst onset of excitatory and inhibitory brain stem saccadic burst neurons (SBNs). Furthermore, the time-varying discharge properties of the majority of SBNs (>70%) preferentially encoded the dynamics of an individual eye during disconjugate saccades. When these experimental results were implemented into a computer-based simulation, to further evaluate the contribution of the saccadic burst generator in generating disconjugate saccades, we found that it carries all the vergence drive that is necessary to shape the activity of the abducens motoneurons to which it projects. Taken together, our results provide evidence that the premotor commands from the brain stem saccadic circuitry, to the target motoneurons, are sufficient to ensure the accurate control shifts of gaze in three dimensions.

Short-duration stimulation of the supplementary eye fields perturbs anti-saccade performance while potentiating contralateral head orienting.

PubMed

Chapman, Brendan B; Corneil, Brian D

2014-01-01

Many forms of brain stimulation utilize the notion of state dependency, whereby greater influences are observed when a given area is more engaged at the time of stimulation. Here, by delivering intracortical microstimulation (ICMS) to the supplementary eye fields (SEF) of monkeys performing interleaved pro- and anti-saccades, we show a surprising diversity of state-dependent effects of ICMS-SEF. Short-duration ICMS-SEF passed around cue presentation selectively disrupted anti-saccades by increasing reaction times and error rates bilaterally, and also recruited neck muscles, favoring contralateral head turning to a greater degree on anti-saccade trials. These results are consistent with the functional relevance of the SEF for anti-saccades. The multiplicity of stimulation-evoked effects, with ICMS-SEF simultaneously disrupting anti-saccade performance and facilitating contralateral head orienting, probably reflects both the diversity of cortical and subcortical targets of SEF projections, and the response of this oculomotor network to stimulation. We speculate that the bilateral disruption of anti-saccades arises via feedback loops that may include the thalamus, whereas neck muscle recruitment arises via feedforward polysynaptic pathways to the motor periphery. Consideration of both sets of results reveals a more complete picture of the highly complex and multiphasic response to ICMS-SEF that can play out differently in different effector systems.

Presaccadic perceptual facilitation effects depend on saccade execution: evidence from the stop-signal paradigm.

PubMed

Born, Sabine; Mottet, Isaline; Kerzel, Dirk

2014-03-05

Prior to the onset of a saccadic eye movement, perception is facilitated at the saccade target location. This has been attributed to a shift of attention. To test whether presaccadic attention shifts are strictly dependent on saccade execution, we examined whether they are found when observers are required to cancel the eye movement. We combined a dual task with the stop-signal paradigm: Subjects made saccades as quickly as possible to a cued location while discriminating a stimulus either at the saccade target or at the opposite location. A stop signal was presented on a subset of trials, asking subjects to cancel the eye movement. The delay of the stop signal was adjusted to yield successful inhibition of the saccade in 50% of trials. Results show similar perceptual facilitation at the saccade target for saccades with or without a stop signal, suggesting that presaccadic attention shifts are obligatory for all saccades. However, there was facilitation only when saccades were actually performed, not when observers successfully inhibited them. Thus, preparing an eye movement without subsequently executing it does not result in an attention shift. The results speak to a difference between saccade preparation and saccade programming. In light of the strong dependence on saccade execution, we discuss the functional role and causes of presaccadic attention shifts.

Saccade Generation by the Frontal Eye Fields in Rhesus Monkeys Is Separable from Visual Detection and Bottom-Up Attention Shift

PubMed Central

Lee, Kyoung-Min; Ahn, Kyung-Ha; Keller, Edward L.

2012-01-01

The frontal eye fields (FEF), originally identified as an oculomotor cortex, have also been implicated in perceptual functions, such as constructing a visual saliency map and shifting visual attention. Further dissecting the area’s role in the transformation from visual input to oculomotor command has been difficult because of spatial confounding between stimuli and responses and consequently between intermediate cognitive processes, such as attention shift and saccade preparation. Here we developed two tasks in which the visual stimulus and the saccade response were dissociated in space (the extended memory-guided saccade task), and bottom-up attention shift and saccade target selection were independent (the four-alternative delayed saccade task). Reversible inactivation of the FEF in rhesus monkeys disrupted, as expected, contralateral memory-guided saccades, but visual detection was demonstrated to be intact at the same field. Moreover, saccade behavior was impaired when a bottom-up shift of attention was not a prerequisite for saccade target selection, indicating that the inactivation effect was independent of the previously reported dysfunctions in bottom-up attention control. These findings underscore the motor aspect of the area’s functions, especially in situations where saccades are generated by internal cognitive processes, including visual short-term memory and long-term associative memory. PMID:22761923

Saccade generation by the frontal eye fields in rhesus monkeys is separable from visual detection and bottom-up attention shift.

PubMed

Lee, Kyoung-Min; Ahn, Kyung-Ha; Keller, Edward L

2012-01-01

The frontal eye fields (FEF), originally identified as an oculomotor cortex, have also been implicated in perceptual functions, such as constructing a visual saliency map and shifting visual attention. Further dissecting the area's role in the transformation from visual input to oculomotor command has been difficult because of spatial confounding between stimuli and responses and consequently between intermediate cognitive processes, such as attention shift and saccade preparation. Here we developed two tasks in which the visual stimulus and the saccade response were dissociated in space (the extended memory-guided saccade task), and bottom-up attention shift and saccade target selection were independent (the four-alternative delayed saccade task). Reversible inactivation of the FEF in rhesus monkeys disrupted, as expected, contralateral memory-guided saccades, but visual detection was demonstrated to be intact at the same field. Moreover, saccade behavior was impaired when a bottom-up shift of attention was not a prerequisite for saccade target selection, indicating that the inactivation effect was independent of the previously reported dysfunctions in bottom-up attention control. These findings underscore the motor aspect of the area's functions, especially in situations where saccades are generated by internal cognitive processes, including visual short-term memory and long-term associative memory.

Quantitative analysis of catch-up saccades during sustained pursuit.

PubMed

de Brouwer, Sophie; Missal, Marcus; Barnes, Graham; Lefèvre, Philippe

2002-04-01

During visual tracking of a moving stimulus, primates orient their visual axis by combining two very different types of eye movements, smooth pursuit and saccades. The purpose of this paper was to investigate quantitatively the catch-up saccades occurring during sustained pursuit. We used a ramp-step-ramp paradigm to evoke catch-up saccades during sustained pursuit. In general, catch-up saccades followed the unexpected steps in position and velocity of the target. We observed catch-up saccades in the same direction as the smooth eye movement (forward saccades) as well as in the opposite direction (reverse saccades). We made a comparison of the main sequences of forward saccades, reverse saccades, and control saccades made to stationary targets. They were all three significantly different from each other and were fully compatible with the hypothesis that the smooth pursuit component is added to the saccadic component during catch-up saccades. A multiple linear regression analysis was performed on the saccadic component to find the parameters determining the amplitude of catch-up saccades. We found that both position error and retinal slip are taken into account in catch-up saccade programming to predict the future trajectory of the moving target. We also demonstrated that the saccadic system needs a minimum period of approximately 90 ms for taking into account changes in target trajectory. Finally, we reported a saturation (above 15 degrees /s) in the contribution of retinal slip to the amplitude of catch-up saccades.

Immediate Neural Plasticity Involving Reaction Time in a Saccadic Eye Movement Task is Intact in Children With Fetal Alcohol Spectrum Disorder.

PubMed

Paolozza, Angelina; Munoz, Douglas P; Brien, Donald; Reynolds, James N

2016-11-01

Saccades are rapid eye movements that bring an image of interest onto the retina. Previous research has found that in healthy individuals performing eye movement tasks, the location of a previous visual target can influence performance of the saccade on the next trial. This rapid behavioral adaptation represents a form of immediate neural plasticity within the saccadic circuitry. Our studies have shown that children with fetal alcohol spectrum disorder (FASD) are impaired on multiple saccade measures. We therefore investigated these previous trial effects in typically developing children and children with FASD to measure sensory neural plasticity and how these effects vary with age and pathology. Both typically developing control children (n = 102; mean age = 10.54 ± 3.25; 48 males) and children with FASD (n = 66; mean age = 11.85 ± 3.42; 35 males) were recruited from 5 sites across Canada. Each child performed a visually guided saccade task. Reaction time and saccade amplitude were analyzed and then assessed based on the previous trial. There was a robust previous trial effect for both reaction time and amplitude, with both the control and FASD groups displaying faster reaction times and smaller saccades during alternation trials (visual target presented on the opposite side to the previous trial). Children with FASD exhibited smaller overall mean amplitude and smaller amplitude selectively on alternation trials compared with controls. The effect of the previous trial on reaction time and amplitude did not differ across childhood and adolescent development. Children with FASD did not display any significant reaction time differences, despite exhibiting numerous deficits in motor and higher level cognitive control over saccades in other studies. These results suggest that this form of immediate neural plasticity in response to sensory information before saccade initiation remains intact in children with FASD. In contrast, the previous trial effect on

Validation of a Behavioral Approach for Measuring Saccades in Parkinson's Disease.

PubMed

Turner, Travis H; Renfroe, Jenna B; Duppstadt-Delambo, Amy; Hinson, Vanessa K

2017-01-01

Speed and control of saccades are related to disease progression and cognitive functioning in Parkinson's disease (PD). Traditional eye-tracking complexities encumber application for individual evaluations and clinical trials. The authors examined psychometric properties of standalone tasks for reflexive prosaccade latency, volitional saccade initiation, and saccade inhibition (antisaccade) in a heterogeneous sample of 65 PD patients. Demographics had minimal impact on task performance. Thirty-day test-retest reliability estimates for behavioral tasks were acceptable and similar to traditional eye tracking. Behavioral tasks demonstrated concurrent validity with traditional eye-tracking measures; discriminant validity was less clear. Saccade initiation and inhibition discriminated PD patients with cognitive impairment. The present findings support further development and use of the behavioral tasks for assessing latency and control of saccades in PD.

Cognitive regulation of saccadic velocity by reward prospect.

PubMed

Chen, Lewis L; Hung, Leroy Y; Quinet, Julie; Kosek, Kevin

2013-08-01

It is known that expectation of reward speeds up saccades. Past studies have also shown the presence of a saccadic velocity bias in the orbit, resulting from a biomechanical regulation over varying eccentricities. Nevertheless, whether and how reward expectation interacts with the biomechanical regulation of saccadic velocities over varying eccentricities remains unknown. We addressed this question by conducting a visually guided double-step saccade task. The role of reward expectation was tested in monkeys performing two consecutive horizontal saccades, one associated with reward prospect and the other not. To adequately assess saccadic velocity and avoid adaptation, we systematically varied initial eye positions, saccadic directions and amplitudes. Our results confirmed the existence of a velocity bias in the orbit, i.e., saccadic peak velocity decreased linearly as the initial eye position deviated in the direction of the saccade. The slope of this bias increased as saccadic amplitudes increased. Nevertheless, reward prospect facilitated velocity to a greater extent for saccades away from than for saccades toward the orbital centre, rendering an overall reduction in the velocity bias. The rate (slope) and magnitude (intercept) of reward modulation over this velocity bias were linearly correlated with amplitudes, similar to the amplitude-modulated velocity bias without reward prospect, which presumably resulted from a biomechanical regulation. Small-amplitude (≤ 5°) saccades received little modulation. These findings together suggest that reward expectation modulated saccadic velocity not as an additive signal but as a facilitating mechanism that interacted with the biomechanical regulation. © 2013 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.

An Attention-Sensitive Memory Trace in Macaque MT Following Saccadic Eye Movements

PubMed Central

Yao, Tao; Treue, Stefan; Krishna, B. Suresh

2016-01-01

We experience a visually stable world despite frequent retinal image displacements induced by eye, head, and body movements. The neural mechanisms underlying this remain unclear. One mechanism that may contribute is transsaccadic remapping, in which the responses of some neurons in various attentional, oculomotor, and visual brain areas appear to anticipate the consequences of saccades. The functional role of transsaccadic remapping is actively debated, and many of its key properties remain unknown. Here, recording from two monkeys trained to make a saccade while directing attention to one of two spatial locations, we show that neurons in the middle temporal area (MT), a key locus in the motion-processing pathway of humans and macaques, show a form of transsaccadic remapping called a memory trace. The memory trace in MT neurons is enhanced by the allocation of top-down spatial attention. Our data provide the first demonstration, to our knowledge, of the influence of top-down attention on the memory trace anywhere in the brain. We find evidence only for a small and transient effect of motion direction on the memory trace (and in only one of two monkeys), arguing against a role for MT in the theoretically critical yet empirically contentious phenomenon of spatiotopic feature-comparison and adaptation transfer across saccades. Our data support the hypothesis that transsaccadic remapping represents the shift of attentional pointers in a retinotopic map, so that relevant locations can be tracked and rapidly processed across saccades. Our results resolve important issues concerning the perisaccadic representation of visual stimuli in the dorsal stream and demonstrate a significant role for top-down attention in modulating this representation. PMID:26901857

Measuring saccade peak velocity using a low-frequency sampling rate of 50 Hz.

PubMed

Wierts, Roel; Janssen, Maurice J A; Kingma, Herman

2008-12-01

During the last decades, small head-mounted video eye trackers have been developed in order to record eye movements. Real-time systems-with a low sampling frequency of 50/60 Hz-are used for clinical vestibular practice, but are generally considered not to be suited for measuring fast eye movements. In this paper, it is shown that saccadic eye movements, having an amplitude of at least 5 degrees, can, in good approximation, be considered to be bandwidth limited up to a frequency of 25-30 Hz. Using the Nyquist theorem to reconstruct saccadic eye movement signals at higher temporal resolutions, it is shown that accurate values for saccade peak velocities, recorded at 50 Hz, can be obtained, but saccade peak accelerations and decelerations cannot. In conclusion, video eye trackers sampling at 50/60 Hz are appropriate for detecting the clinical relevant saccade peak velocities in contrast to what has been stated up till now.

The influence of crystalline lens accommodation on post-saccadic oscillations in pupil-based eye trackers.

PubMed

Nyström, Marcus; Andersson, Richard; Magnusson, Måns; Pansell, Tony; Hooge, Ignace

2015-02-01

It is well known that the crystalline lens (henceforth lens) can oscillate (or 'wobble') relative to the eyeball at the end of saccades. Recent research has proposed that such wobbling of the lens is a source of post-saccadic oscillations (PSOs) seen in data recorded by eye trackers that estimate gaze direction from the location of the pupil. Since the size of the lens wobbles increases with accommodative effort, one would predict a similar increase of PSO-amplitude in data recorded with a pupil based eye tracker. In four experiments, we investigated the role of lens accommodation on PSOs in a video-based eye tracker. In Experiment 1, we replicated previous results showing that PSO-amplitudes increase at near viewing distances (large vergence angles), when the lens is highly accommodated. In Experiment 2a, we manipulated the accommodative state of the lens pharmacologically using eye drops at a fixed viewing distance and found, in contrast to Experiment 1, no significant difference in PSO-amplitude related to the accommodative state of the lens. Finally, in Experiment 2b, the effect of vergence angle was investigated by comparing PSO-amplitudes at near and far while maintaining a fixed lens accommodation. Despite the pharmacologically fixed degree of accommodation, PSO-amplitudes were systematically larger in the near condition. In summary, PSOs cannot exhaustively be explained by lens wobbles. Possible confounds related to pupil size and eye-camera angle are investigated in Experiments 3 and 4, and alternative mechanisms behind PSOs are probed in the discussion. Copyright © 2014 Elsevier Ltd. All rights reserved.

Differences in saccadic eye movements in subjects at high and low risk for panic disorder.

PubMed

Zwanzger, Peter; Bradwejn, Jacques; Diemer, Julia; Marshall, Roger W; Koszycki, Diana

2012-01-01

Panic disorder (PD) has a strong genetic component showing high heritability rates and familial aggregation. Moreover, there is evidence for associations between parental PD and patterns of psychopathology. So far, little is known about possible endophenotypes representing premorbid vulnerability markers in high-risk subjects for PD. In the present study, we investigated saccadic eye movement (SEM) as an index of CNS inhibitory function in subjects at high risk for PD. 132 healthy children at high and low familial risk for PD were included in the study. Basal SEM parameters were obtained using an electro-oculography (EOG) based system measuring peak saccadic eye velocity (pSEV), latency and accuracy. Moreover, with regard to self rating scales, state-trait-anxiety (STAI-C), childhood behavioral inhibition (CSRI), and anxiety sensitivity (CASI) were assessed. There was a significant overall difference for basal SEM parameters across groups as revealed by MANCOVA (F7,118=2.184, p=.040). A significant influence was found for the covariate age, while gender and puberty status had no influence on SEM. High-risk (HR) subjects showed significantly lower pSEV. Moreover, levels of state and trait anxiety were higher in HR children (F1=5.429, p=.021). In our sample, measurement of pSEV allowed discrimination between children at high and low risk for PD. Since these results argue for possible alterations of saccadic function in high risk subjects, differences in underlying neurobiological mechanisms might be discussed as a possible endophenotype of PD.

Dynamic modulation of ocular orientation during visually guided saccades and smooth-pursuit eye movements

NASA Technical Reports Server (NTRS)

Hess, Bernhard J M.; Angelaki, Dora E.

2003-01-01

Rotational disturbances of the head about an off-vertical yaw axis induce a complex vestibuloocular reflex pattern that reflects the brain's estimate of head angular velocity as well as its estimate of instantaneous head orientation (at a reduced scale) in space coordinates. We show that semicircular canal and otolith inputs modulate torsional and, to a certain extent, also vertical ocular orientation of visually guided saccades and smooth-pursuit eye movements in a similar manner as during off-vertical axis rotations in complete darkness. It is suggested that this graviceptive control of eye orientation facilitates rapid visual spatial orientation during motion.

First saccadic eye movement reveals persistent attentional guidance by implicit learning

PubMed Central

Jiang, Yuhong V.; Won, Bo-Yeong; Swallow, Khena M.

2014-01-01

Implicit learning about where a visual search target is likely to appear often speeds up search. However, whether implicit learning guides spatial attention or affects post-search decisional processes remains controversial. Using eye tracking, this study provides compelling evidence that implicit learning guides attention. In a training phase, participants often found the target in a high-frequency, “rich” quadrant of the display. When subsequently tested in a phase during which the target was randomly located, participants were twice as likely to direct the first saccadic eye movement to the previously rich quadrant than to any of the sparse quadrants. The attentional bias persisted for nearly 200 trials after training and was unabated by explicit instructions to distribute attention evenly. We propose that implicit learning guides spatial attention but in a qualitatively different manner than goal-driven attention. PMID:24512610

Quick Phases of Infantile Nystagmus Show the Saccadic Inhibition Effect

PubMed Central

Harrison, James J.; Sumner, Petroc; Dunn, Matt J.; Erichsen, Jonathan T.; Freeman, Tom C. A.

2015-01-01

Purpose. Infantile nystagmus (IN) is a pathological, involuntary oscillation of the eyes consisting of slow, drifting eye movements interspersed with rapid reorienting quick phases. The extent to which quick phases of IN are programmed similarly to saccadic eye movements remains unknown. We investigated whether IN quick phases exhibit ‘saccadic inhibition,' a phenomenon typically related to normal targeting saccades, in which the initiation of the eye movement is systematically delayed by task-irrelevant visual distractors. Methods. We recorded eye position from 10 observers with early-onset idiopathic nystagmus while task-irrelevant distractor stimuli were flashed along the top and bottom of a large screen at ±10° eccentricity. The latency distributions of quick phases were measured with respect to these distractor flashes. Two additional participants, one with possible albinism and one with fusion maldevelopment nystagmus syndrome, were also tested. Results. All observers showed that a distractor flash delayed the execution of quick phases that would otherwise have occurred approximately 100 ms later, exactly as in the standard saccadic inhibition effect. The delay did not appear to differ between the two main nystagmus types under investigation (idiopathic IN with unidirectional and bidirectional jerk). Conclusions. The presence of the saccadic inhibition effect in IN quick phases is consistent with the idea that quick phases and saccades share a common programming pathway. This could allow quick phases to take on flexible, goal-directed behavior, at odds with the view that IN quick phases are stereotyped, involuntary eye movements. PMID:25670485

Effects of Saccadic Bilateral Eye Movements on Memory in Children and Adults: An Exploratory Study

ERIC Educational Resources Information Center

Parker, Andrew; Dagnall, Neil

2012-01-01

The effects of saccadic bilateral (horizontal) eye movements on true and false memory in adults and children were investigated. Both adults and children encoded lists of associated words in the Deese-Roediger-McDermott paradigm followed by a test of recognition memory. Just prior to retrieval, participants were asked to engage in 30 s of bilateral…

Detection of Stimulus Displacements Across Saccades is Capacity-Limited and Biased in Favor of the Saccade Target

PubMed Central

Irwin, David E.; Robinson, Maria M.

2015-01-01

Retinal image displacements caused by saccadic eye movements are generally unnoticed. Recent theories have proposed that perceptual stability across saccades depends on a local evaluation process centered on the saccade target object rather than on remapping and evaluating the positions of all objects in a display. In three experiments, we examined whether objects other than the saccade target also influence perceptual stability by measuring displacement detection thresholds across saccades for saccade targets and a variable number of non-saccade objects. We found that the positions of multiple objects are maintained across saccades, but with variable precision, with the saccade target object having priority in the perception of displacement, most likely because it is the focus of attention before the saccade and resides near the fovea after the saccade. The perception of displacement of objects that are not the saccade target is affected by acuity limitations, attentional limitations, and limitations on memory capacity. Unlike previous studies that have found that a postsaccadic blank improves the detection of displacement direction across saccades, we found that postsaccadic blanking hurt the detection of displacement per se by increasing false alarms. Overall, our results are consistent with the hypothesis that visual working memory underlies the perception of stability across saccades. PMID:26640430

The neural basis of parallel saccade programming: an fMRI study.

PubMed

Hu, Yanbo; Walker, Robin

2011-11-01

The neural basis of parallel saccade programming was examined in an event-related fMRI study using a variation of the double-step saccade paradigm. Two double-step conditions were used: one enabled the second saccade to be partially programmed in parallel with the first saccade while in a second condition both saccades had to be prepared serially. The intersaccadic interval, observed in the parallel programming (PP) condition, was significantly reduced compared with latency in the serial programming (SP) condition and also to the latency of single saccades in control conditions. The fMRI analysis revealed greater activity (BOLD response) in the frontal and parietal eye fields for the PP condition compared with the SP double-step condition and when compared with the single-saccade control conditions. By contrast, activity in the supplementary eye fields was greater for the double-step condition than the single-step condition but did not distinguish between the PP and SP requirements. The role of the frontal eye fields in PP may be related to the advanced temporal preparation and increased salience of the second saccade goal that may mediate activity in other downstream structures, such as the superior colliculus. The parietal lobes may be involved in the preparation for spatial remapping, which is required in double-step conditions. The supplementary eye fields appear to have a more general role in planning saccade sequences that may be related to error monitoring and the control over the execution of the correct sequence of responses.

No Evidence for a Saccadic Range Effect for Visually Guided and Memory-Guided Saccades in Simple Saccade-Targeting Tasks

PubMed Central

Vitu, Françoise; Engbert, Ralf; Kliegl, Reinhold

2016-01-01

Saccades to single targets in peripheral vision are typically characterized by an undershoot bias. Putting this bias to a test, Kapoula [1] used a paradigm in which observers were presented with two different sets of target eccentricities that partially overlapped each other. Her data were suggestive of a saccadic range effect (SRE): There was a tendency for saccades to overshoot close targets and undershoot far targets in a block, suggesting that there was a response bias towards the center of eccentricities in a given block. Our Experiment 1 was a close replication of the original study by Kapoula [1]. In addition, we tested whether the SRE is sensitive to top-down requirements associated with the task, and we also varied the target presentation duration. In Experiments 1 and 2, we expected to replicate the SRE for a visual discrimination task. The simple visual saccade-targeting task in Experiment 3, entailing minimal top-down influence, was expected to elicit a weaker SRE. Voluntary saccades to remembered target locations in Experiment 3 were expected to elicit the strongest SRE. Contrary to these predictions, we did not observe a SRE in any of the tasks. Our findings complement the results reported by Gillen et al. [2] who failed to find the effect in a saccade-targeting task with a very brief target presentation. Together, these results suggest that unlike arm movements, saccadic eye movements are not biased towards making saccades of a constant, optimal amplitude for the task. PMID:27658191

Rewards modulate saccade latency but not exogenous spatial attention.

PubMed

Dunne, Stephen; Ellison, Amanda; Smith, Daniel T

2015-01-01

The eye movement system is sensitive to reward. However, whilst the eye movement system is extremely flexible, the extent to which changes to oculomotor behavior induced by reward paradigms persist beyond the training period or transfer to other oculomotor tasks is unclear. To address these issues we examined the effects of presenting feedback that represented small monetary rewards to spatial locations on the latency of saccadic eye movements, the time-course of learning and extinction of the effects of rewarding saccades on exogenous spatial attention and oculomotor inhibition of return. Reward feedback produced a relative facilitation of saccadic latency in a stimulus driven saccade task which persisted for three blocks of extinction trials. However, this hemifield-specific effect failed to transfer to peripheral cueing tasks. We conclude that rewarding specific spatial locations is unlikely to induce long-term, systemic changes to the human oculomotor or attention systems.

Are there any left-right asymmetries in saccade parameters? Examination of latency, gain, and peak velocity.

PubMed

Vergilino-Perez, Dorine; Fayel, Alexandra; Lemoine, Christelle; Senot, Patrice; Vergne, Judith; Doré-Mazars, Karine

2012-06-05

Hemispheric specialization in saccadic control is still under debate. Here we examine the latency, gain, and peak velocity of reactive and voluntary leftward and rightward saccades to assess the respective roles of eye and hand dominance. Participants with contrasting hand and eye dominance were asked to make saccades toward a target displayed at 5°, 10°, or 15° left or right of the central fixation point. In separate sessions, reactive and voluntary saccades were elicited by Gap-200, Gap-0, Overlap-600, and Antisaccade procedures. Left-right asymmetries were not found in saccade latencies but appeared in saccade gain and peak velocity. Regardless of the dominant hand, saccades directed to the ipsilateral side relative to the dominant eye had larger amplitudes and faster peak velocities. Left-right asymmetries can be explained by naso-temporal differences for some subjects and by eye dominance for others. Further investigations are needed to examine saccadic parameters more systematically in relation to eye dominance. Indeed, any method that allows one to determine ocular dominance from objective measures based on saccade parameters should greatly benefit clinical applications, such as monovision surgery.

Medications influencing central cholinergic pathways affect fixation stability, saccadic response time and associated eye movement dynamics during a temporally-cued visual reaction time task.

PubMed

Naicker, Preshanta; Anoopkumar-Dukie, Shailendra; Grant, Gary D; Modenese, Luca; Kavanagh, Justin J

2017-02-01

Anticholinergic medications largely exert their effects due to actions on the muscarinic receptor, which mediates the functions of acetylcholine in the peripheral and central nervous systems. In the central nervous system, acetylcholine plays an important role in the modulation of movement. This study investigated the effects of over-the-counter medications with varying degrees of central anticholinergic properties on fixation stability, saccadic response time and the dynamics associated with this eye movement during a temporally-cued visual reaction time task, in order to establish the significance of central cholinergic pathways in influencing eye movements during reaction time tasks. Twenty-two participants were recruited into the placebo-controlled, human double-blind, four-way crossover investigation. Eye tracking technology recorded eye movements while participants reacted to visual stimuli following temporally informative and uninformative cues. The task was performed pre-ingestion as well as 0.5 and 2 h post-ingestion of promethazine hydrochloride (strong centrally acting anticholinergic), hyoscine hydrobromide (moderate centrally acting anticholinergic), hyoscine butylbromide (anticholinergic devoid of central properties) and a placebo. Promethazine decreased fixation stability during the reaction time task. In addition, promethazine was the only drug to increase saccadic response time during temporally informative and uninformative cued trials, whereby effects on response time were more pronounced following temporally informative cues. Promethazine also decreased saccadic amplitude and increased saccadic duration during the temporally-cued reaction time task. Collectively, the results of the study highlight the significant role that central cholinergic pathways play in the control of eye movements during tasks that involve stimulus identification and motor responses following temporal cues.

Role of retinal slip in the prediction of target motion during smooth and saccadic pursuit.

PubMed

de Brouwer, S; Missal, M; Lefèvre, P

2001-08-01

Visual tracking of moving targets requires the combination of smooth pursuit eye movements with catch-up saccades. In primates, catch-up saccades usually take place only during pursuit initiation because pursuit gain is close to unity. This contrasts with the lower and more variable gain of smooth pursuit in cats, where smooth eye movements are intermingled with catch-up saccades during steady-state pursuit. In this paper, we studied in detail the role of retinal slip in the prediction of target motion during smooth and saccadic pursuit in the cat. We found that the typical pattern of pursuit in the cat was a combination of smooth eye movements with saccades. During smooth pursuit initiation, there was a correlation between peak eye acceleration and target velocity. During pursuit maintenance, eye velocity oscillated at approximately 3 Hz around a steady-state value. The average gain of smooth pursuit was approximately 0.5. Trained cats were able to continue pursuing in the absence of a visible target, suggesting a role of the prediction of future target motion in this species. The analysis of catch-up saccades showed that the smooth-pursuit motor command is added to the saccadic command during catch-up saccades and that both position error and retinal slip are taken into account in their programming. The influence of retinal slip on catch-up saccades showed that prediction about future target motion is used in the programming of catch-up saccades. Altogether, these results suggest that pursuit systems in primates and cats are qualitatively similar, with a lower average gain in the cat and that prediction affects both saccades and smooth eye movements during pursuit.

Short-term saccadic adaptation in the macaque monkey: a binocular mechanism

PubMed Central

Schultz, K. P.

2013-01-01

Saccadic eye movements are rapid transfers of gaze between objects of interest. Their duration is too short for the visual system to be able to follow their progress in time. Adaptive mechanisms constantly recalibrate the saccadic responses by detecting how close the landings are to the selected targets. The double-step saccadic paradigm is a common method to simulate alterations in saccadic gain. While the subject is responding to a first target shift, a second shift is introduced in the middle of this movement, which masks it from visual detection. The error in landing introduced by the second shift is interpreted by the brain as an error in the programming of the initial response, with gradual gain changes aimed at compensating the apparent sensorimotor mismatch. A second shift applied dichoptically to only one eye introduces disconjugate landing errors between the two eyes. A monocular adaptive system would independently modify only the gain of the eye exposed to the second shift in order to reestablish binocular alignment. Our results support a binocular mechanism. A version-based saccadic adaptive process detects postsaccadic version errors and generates compensatory conjugate gain alterations. A vergence-based saccadic adaptive process detects postsaccadic disparity errors and generates corrective nonvisual disparity signals that are sent to the vergence system to regain binocularity. This results in striking dynamical similarities between visually driven combined saccade-vergence gaze transfers, where the disparity is given by the visual targets, and the double-step adaptive disconjugate responses, where an adaptive disparity signal is generated internally by the saccadic system. PMID:23076111

Physiology and pathology of saccades and gaze holding.

PubMed

Shaikh, Aasef G; Ghasia, Fatema F

2013-01-01

Foveation is the fundamental requirement for clear vision. Saccades rapidly shift the gaze to the interesting target while gaze holding ensures foveation of the desired object. We will review the pertinent physiology of saccades and gaze holding and their pathophysiology leading to saccadic oscillations, slow saccades, saccadic dysmetria, and nystagmus. Motor commands for saccades are generated at multiple levels of the neuraxis. The frontal and parietal eye field send saccadic commands to the superior colliculus. Latter then projects to the brain-stem saccadic burst generator. The brain-stem burst generators guarantee optimum signal to ensure rapid saccadic velocity, while the neural integrator, by mathematically integrating the saccadic pulse, facilitates stable gaze holding. Reciprocal innervations that ensure rapid saccadic velocity are prone to inherent instability leading to saccadic oscillations. In contrast, suboptimal function of the burst generators causes slow saccades. Impaired error correction, either at the cerebellum or the inferior olive, leads to impaired saccade adaptation and ultimately saccadic dysmetria and oculopalatal tremor. Impairment in the function of neural integrator causes nystagmus. Neurophysiology of saccades, gaze holding, and their deficits are well recognized. These principles can be implemented to define novel therapeutic and rehabilitation approaches.

A model that integrates eye velocity commands to keep track of smooth eye displacements.

PubMed

Blohm, Gunnar; Optican, Lance M; Lefèvre, Philippe

2006-08-01

Past results have reported conflicting findings on the oculomotor system's ability to keep track of smooth eye movements in darkness. Whereas some results indicate that saccades cannot compensate for smooth eye displacements, others report that memory-guided saccades during smooth pursuit are spatially correct. Recently, it was shown that the amount of time before the saccade made a difference: short-latency saccades were retinotopically coded, whereas long-latency saccades were spatially coded. Here, we propose a model of the saccadic system that can explain the available experimental data. The novel part of this model consists of a delayed integration of efferent smooth eye velocity commands. Two alternative physiologically realistic neural mechanisms for this integration stage are proposed. Model simulations accurately reproduced prior findings. Thus, this model reconciles the earlier contradictory reports from the literature about compensation for smooth eye movements before saccades because it involves a slow integration process.

Abnormal Fixational Eye Movements in Amblyopia.

PubMed

Shaikh, Aasef G; Otero-Millan, Jorge; Kumar, Priyanka; Ghasia, Fatema F

2016-01-01

Fixational saccades shift the foveal image to counteract visual fading related to neural adaptation. Drifts are slow eye movements between two adjacent fixational saccades. We quantified fixational saccades and asked whether their changes could be attributed to pathologic drifts seen in amblyopia, one of the most common causes of blindness in childhood. Thirty-six pediatric subjects with varying severity of amblyopia and eleven healthy age-matched controls held their gaze on a visual target. Eye movements were measured with high-resolution video-oculography during fellow eye-viewing and amblyopic eye-viewing conditions. Fixational saccades and drifts were analyzed in the amblyopic and fellow eye and compared with controls. We found an increase in the amplitude with decreased frequency of fixational saccades in children with amblyopia. These alterations in fixational eye movements correlated with the severity of their amblyopia. There was also an increase in eye position variance during drifts in amblyopes. There was no correlation between the eye position variance or the eye velocity during ocular drifts and the amplitude of subsequent fixational saccade. Our findings suggest that abnormalities in fixational saccades in amblyopia are independent of the ocular drift. This investigation of amblyopia in pediatric age group quantitatively characterizes the fixation instability. Impaired properties of fixational saccades could be the consequence of abnormal processing and reorganization of the visual system in amblyopia. Paucity in the visual feedback during amblyopic eye-viewing condition can attribute to the increased eye position variance and drift velocity.

Timing of saccadic eye movements during visual search for multiple targets

PubMed Central

Wu, Chia-Chien; Kowler, Eileen

2013-01-01

Visual search requires sequences of saccades. Many studies have focused on spatial aspects of saccadic decisions, while relatively few (e.g., Hooge & Erkelens, 1999) consider timing. We studied saccadic timing during search for targets (thin circles containing tilted lines) located among nontargets (thicker circles). Tasks required either (a) estimating the mean tilt of the lines, or (b) looking at targets without a concurrent psychophysical task. The visual similarity of targets and nontargets affected both the probability of hitting a target and the saccade rate in both tasks. Saccadic timing also depended on immediate conditions, specifically, (a) the type of currently fixated location (dwell time was longer on targets than nontargets), (b) the type of goal (dwell time was shorter prior to saccades that hit targets), and (c) the ordinal position of the saccade in the sequence. The results show that timing decisions take into account the difficulty of finding targets, as well as the cost of delays. Timing strategies may be a compromise between the attempt to find and locate targets, or other suitable landing locations, using eccentric vision (at the cost of increased dwell times) versus a strategy of exploring less selectively at a rapid rate. PMID:24049045

Saccadic velocity measurements in strabismus.

PubMed Central

Metz, H S

1983-01-01

Traditional evaluation of strabismus has included cover test measurements, evaluation of the range of ocular rotations, and an array of subjective sensory tests. These studies could not always differentiate paresis of an extraocular muscle from restrictions and from various neuro-ophthalmic motility disorders. The measurement of horizontal and vertical saccadic movements can provide an objective test of rectus muscle function. Using EOG, saccades can be recorded easily, inexpensively, and repeatably at any age. In ocular muscle paresis or paralysis, saccadic speed is reduced mildly to markedly and can be used to monitor recovery. Assessment of saccadic velocity does not appear useful in evaluating superior oblique palsy, although it is valuable in sixth nerve palsy, Duane's syndrome, and third nerve palsy. When restrictions are the major cause of limited rotation, as in thyroid ophthalmopathy and orbital floor fracture, saccadic speed is unaffected. The induction of OKN or vestibular nystagmus is helpful in the study of children too young to perform voluntary saccadic movements. In patients with limitation of elevation or depression, this technique can separate innervational from mechanical causes of diminished rotation. The specific saccadic velocity pattern in myasthenia gravis, progressive external ophthalmoplegia, internuclear ophthalmoplegia, and Möbius' syndrome is helpful in differentiating these disorders from other neuroophthalmic motility problems. Transposition surgery of the rectus muscle is effective because of an increase in force, seen as an improvement in saccadic velocity and resulting from the change of insertion of the muscles. Saccadic velocities can also be of assistance in diagnosing a lost or disinserted muscle following surgery for strabismus. Although analysis of saccadic velocity is not required for the proper evaluation of all problems in strabismus and motility, it can be of inestimable value in the diagnosis of many complex and

A cortical substrate for the long-term memory of saccadic eye movements calibration.

PubMed

Pélisson, Denis; Habchi, Ouazna; Panouillères, Muriel T N; Hernoux, Charles; Farnè, Alessandro

2018-06-19

How movements are continuously adapted to physiological and environmental changes is a fundamental question in systems neuroscience. While many studies have elucidated the mechanisms which underlie short-term sensorimotor adaptation (∼10-30 min), how these motor memories are maintained over longer-term (>3-5 days) -and thanks to which neural systems-is virtually unknown. Here, we examine in healthy human participants whether the temporo-parietal junction (TPJ) is causally involved in the induction and/or the retention of saccadic eye movements' adaptation. Single-pulse transcranial magnetic stimulation (spTMS) was applied while subjects performed a ∼15min size-decrease adaptation task of leftward reactive saccades. A TMS pulse was delivered over the TPJ in the right hemisphere (rTPJ) in each trial either 30, 60, 90 or 120 msec (in 4 separate adaptation sessions) after the saccade onset. In two control groups of subjects, the same adaptation procedure was achieved either alone (No-TMS) or combined with spTMS applied over the vertex (SHAM-TMS). While the timing of spTMS over the rTPJ did not significantly affect the speed and immediate after-effect of adaptation, we found that the amount of adaptation retention measured 10 days later was markedly larger (42%) than in both the No-TMS (21%) and the SHAM-TMS (11%) control groups. These results demonstrate for the first time that the cerebral cortex is causally involved in maintaining long-term oculomotor memories. Copyright © 2018. Published by Elsevier Inc.

Saccadic interception of a moving visual target after a spatiotemporal perturbation.

PubMed

Fleuriet, Jérome; Goffart, Laurent

2012-01-11

Animals can make saccadic eye movements to intercept a moving object at the right place and time. Such interceptive saccades indicate that, despite variable sensorimotor delays, the brain is able to estimate the current spatiotemporal (hic et nunc) coordinates of a target at saccade end. The present work further tests the robustness of this estimate in the monkey when a change in eye position and a delay are experimentally added before the onset of the saccade and in the absence of visual feedback. These perturbations are induced by brief microstimulation in the deep superior colliculus (dSC). When the microstimulation moves the eyes in the direction opposite to the target motion, a correction saccade brings gaze back on the target path or very near. When it moves the eye in the same direction, the performance is more variable and depends on the stimulated sites. Saccades fall ahead of the target with an error that increases when the stimulation is applied more caudally in the dSC. The numerous cases of compensation indicate that the brain is able to maintain an accurate and robust estimate of the location of the moving target. The inaccuracies observed when stimulating the dSC that encodes the visual field traversed by the target indicate that dSC microstimulation can interfere with signals encoding the target motion path. The results are discussed within the framework of the dual-drive and the remapping hypotheses.

The effect of different brightness conditions on visually and memory guided saccades.

PubMed

Felßberg, Anna-Maria; Dombrowe, Isabel

2018-01-01

It is commonly assumed that saccades in the dark are slower than saccades in a lit room. Early studies that investigated this issue using electrooculography (EOG) often compared memory guided saccades in darkness to visually guided saccades in an illuminated room. However, later studies showed that memory guided saccades are generally slower than visually guided saccades. Research on this topic is further complicated by the fact that the different existing eyetracking methods do not necessarily lead to consistent measurements. In the present study, we independently manipulated task (memory guided/visually guided) and screen brightness (dark, medium and light) in an otherwise completely dark room, and measured the peak velocity and the duration of the participant's saccades using a popular pupil-cornea reflection (p-cr) eyetracker (Eyelink 1000). Based on a critical reading of the literature, including a recent study using cornea-reflection (cr) eye tracking, we did not expect any velocity or duration differences between the three brightness conditions. We found that memory guided saccades were generally slower than visually guided saccades. In both tasks, eye movements on a medium and light background were equally fast and had similar durations. However, saccades on the dark background were slower and had shorter durations, even after we corrected for the effect of pupil size changes. This means that this is most likely an artifact of current pupil-based eye tracking. We conclude that the common assumption that saccades in the dark are slower than in the light is probably not true, however pupil-based eyetrackers tend to underestimate the peak velocity of saccades on very dark backgrounds, creating the impression that this might be the case. Copyright © 2017 Elsevier Ltd. All rights reserved.

Spatial attention during saccade decisions.

PubMed

Jonikaitis, Donatas; Klapetek, Anna; Deubel, Heiner

2017-07-01

Behavioral measures of decision making are usually limited to observations of decision outcomes. In the present study, we made use of the fact that oculomotor and sensory selection are closely linked to track oculomotor decision making before oculomotor responses are made. We asked participants to make a saccadic eye movement to one of two memorized target locations and observed that visual sensitivity increased at both the chosen and the nonchosen saccade target locations, with a clear bias toward the chosen target. The time course of changes in visual sensitivity was related to saccadic latency, with the competition between the chosen and nonchosen targets resolved faster before short-latency saccades. On error trials, we observed an increased competition between the chosen and nonchosen targets. Moreover, oculomotor selection and visual sensitivity were influenced by top-down and bottom-up factors as well as by selection history and predicted the direction of saccades. Our findings demonstrate that saccade decisions have direct visual consequences and show that decision making can be traced in the human oculomotor system well before choices are made. Our results also indicate a strong association between decision making, saccade target selection, and visual sensitivity. NEW & NOTEWORTHY We show that saccadic decisions can be tracked by measuring spatial attention. Spatial attention is allocated in parallel to the two competing saccade targets, and the time course of spatial attention differs for fast-slow and for correct-erroneous decisions. Saccade decisions take the form of a competition between potential saccade goals, which is associated with spatial attention allocation to those locations. Copyright © 2017 the American Physiological Society.

Abnormal Fixational Eye Movements in Amblyopia

PubMed Central

Shaikh, Aasef G.; Otero-Millan, Jorge; Kumar, Priyanka; Ghasia, Fatema F.

2016-01-01

Purpose Fixational saccades shift the foveal image to counteract visual fading related to neural adaptation. Drifts are slow eye movements between two adjacent fixational saccades. We quantified fixational saccades and asked whether their changes could be attributed to pathologic drifts seen in amblyopia, one of the most common causes of blindness in childhood. Methods Thirty-six pediatric subjects with varying severity of amblyopia and eleven healthy age-matched controls held their gaze on a visual target. Eye movements were measured with high-resolution video-oculography during fellow eye-viewing and amblyopic eye-viewing conditions. Fixational saccades and drifts were analyzed in the amblyopic and fellow eye and compared with controls. Results We found an increase in the amplitude with decreased frequency of fixational saccades in children with amblyopia. These alterations in fixational eye movements correlated with the severity of their amblyopia. There was also an increase in eye position variance during drifts in amblyopes. There was no correlation between the eye position variance or the eye velocity during ocular drifts and the amplitude of subsequent fixational saccade. Our findings suggest that abnormalities in fixational saccades in amblyopia are independent of the ocular drift. Discussion This investigation of amblyopia in pediatric age group quantitatively characterizes the fixation instability. Impaired properties of fixational saccades could be the consequence of abnormal processing and reorganization of the visual system in amblyopia. Paucity in the visual feedback during amblyopic eye-viewing condition can attribute to the increased eye position variance and drift velocity. PMID:26930079

Human Visual Search Does Not Maximize the Post-Saccadic Probability of Identifying Targets

PubMed Central

Morvan, Camille; Maloney, Laurence T.

2012-01-01

Researchers have conjectured that eye movements during visual search are selected to minimize the number of saccades. The optimal Bayesian eye movement strategy minimizing saccades does not simply direct the eye to whichever location is judged most likely to contain the target but makes use of the entire retina as an information gathering device during each fixation. Here we show that human observers do not minimize the expected number of saccades in planning saccades in a simple visual search task composed of three tokens. In this task, the optimal eye movement strategy varied, depending on the spacing between tokens (in the first experiment) or the size of tokens (in the second experiment), and changed abruptly once the separation or size surpassed a critical value. None of our observers changed strategy as a function of separation or size. Human performance fell far short of ideal, both qualitatively and quantitatively. PMID:22319428

Saccadic Eye Movement Improves Plantar Sensation and Postural Balance in Elderly Women.

PubMed

Bae, Youngsook

2016-06-01

Vision, proprioception and plantar sensation contribute to the control of postural balance (PB). Reduced plantar sensation alters postural response and is at an increased risk of fall, and eye movements reduce the postural sway. Therefore, the aim of this study was to study the improvement of plantar sensation and PB after saccadic eye movement (SEM) and pursuit eye movement (PEM) in community-dwelling elderly women. Participants (104 females; 75.11 ± 6.25 years) were randomly allocated into the SEM group (n = 52) and PEM groups (n = 52). The SEM group performed eye fixation and SEM for 5 minutes, and the PEM group performed eye fixation and PEM for 5 minutes. The plantar sensation was measured according to the plantar surface area of the feet in contact with the floor surface before and after the intervention. Before and after SEM and PEM with the eyes open and closed, PB was measured as the area (mm(2)), length (cm), and velocity (cm/s) of the fluctuation of the center of pressure (COP). The plantar sensation of both feet improved in both groups (p < 0.01). Significant decreases in the area, length, and velocity of the COP were observed in the eye open and close in both groups (p < 0.01). The length and velocity of the COP significantly decreased in the SEM group compared to the PEM group (p < 0.05). In conclusion, SEM and PEM are effective interventions for improving plantar sensation and PB in elderly women, with greater PB improvement after SEM.

Temporal order judgments are disrupted more by reflexive than by voluntary saccades.

PubMed

Yabe, Yoshiko; Goodale, Melvyn A; Shigemasu, Hiroaki

2014-05-01

We do not always perceive the sequence of events as they actually unfold. For example, when two events occur before a rapid eye movement (saccade), the interval between them is often perceived as shorter than it really is and the order of those events can be sometimes reversed (Morrone MC, Ross J, Burr DC. Nat Neurosci 8: 950-954, 2005). In the present article we show that these misperceptions of the temporal order of events critically depend on whether the saccade is reflexive or voluntary. In the first experiment, participants judged the temporal order of two visual stimuli that were presented one after the other just before a reflexive or voluntary saccadic eye movement. In the reflexive saccade condition, participants moved their eyes to a target that suddenly appeared. In the voluntary saccade condition, participants moved their eyes to a target that was present already. Similarly to the above-cited study, we found that the temporal order of events was often misjudged just before a reflexive saccade to a suddenly appearing target. However, when people made a voluntary saccade to a target that was already present, there was a significant reduction in the probability of misjudging the temporal order of the same events. In the second experiment, the reduction was seen in a memory-delay task. It is likely that the nature of the motor command and its origin determine how time is perceived during the moments preceding the motor act. Copyright © 2014 the American Physiological Society.

Oculomotor Evidence for Top-Down Control following the Initial Saccade

PubMed Central

Siebold, Alisha; van Zoest, Wieske; Donk, Mieke

2011-01-01

The goal of the current study was to investigate how salience-driven and goal-driven processes unfold during visual search over multiple eye movements. Eye movements were recorded while observers searched for a target, which was located on (Experiment 1) or defined as (Experiment 2) a specific orientation singleton. This singleton could either be the most, medium, or least salient element in the display. Results were analyzed as a function of response time separately for initial and second eye movements. Irrespective of the search task, initial saccades elicited shortly after the onset of the search display were primarily salience-driven whereas initial saccades elicited after approximately 250 ms were completely unaffected by salience. Initial saccades were increasingly guided in line with task requirements with increasing response times. Second saccades were completely unaffected by salience and were consistently goal-driven, irrespective of response time. These results suggest that stimulus-salience affects the visual system only briefly after a visual image enters the brain and has no effect thereafter. PMID:21931603

Saccadic eye movements do not disrupt the deployment of feature-based attention.

PubMed

Kalogeropoulou, Zampeta; Rolfs, Martin

2017-07-01

The tight link of saccades to covert spatial attention has been firmly established, yet their relation to other forms of visual selection remains poorly understood. Here we studied the temporal dynamics of feature-based attention (FBA) during fixation and across saccades. Participants reported the orientation (on a continuous scale) of one of two sets of spatially interspersed Gabors (black or white). We tested performance at different intervals between the onset of a colored cue (black or white, indicating which stimulus was the most probable target; red: neutral condition) and the stimulus. FBA built up after cue onset: Benefits (errors for valid vs. neutral cues), costs (invalid vs. neutral), and the overall cueing effect (valid vs. invalid) increased with the cue-stimulus interval. Critically, we also tested visual performance at different intervals after a saccade, when FBA had been fully deployed before saccade initiation. Cueing effects were evident immediately after the saccade and were predicted most accurately and most precisely by fully deployed FBA, indicating that FBA was continuous throughout saccades. Finally, a decomposition of orientation reports into target reports and random guesses confirmed continuity of report precision and guess rates across the saccade. We discuss the role of FBA in perceptual continuity across saccades.

Kinesthetic information facilitates saccades towards proprioceptive-tactile targets.

PubMed

Voudouris, Dimitris; Goettker, Alexander; Mueller, Stefanie; Fiehler, Katja

2016-05-01

Saccades to somatosensory targets have longer latencies and are less accurate and precise than saccades to visual targets. Here we examined how different somatosensory information influences the planning and control of saccadic eye movements. Participants fixated a central cross and initiated a saccade as fast as possible in response to a tactile stimulus that was presented to either the index or the middle fingertip of their unseen left hand. In a static condition, the hand remained at a target location for the entire block of trials and the stimulus was presented at a fixed time after an auditory tone. Therefore, the target location was derived only from proprioceptive and tactile information. In a moving condition, the hand was first actively moved to the same target location and the stimulus was then presented immediately. Thus, in the moving condition additional kinesthetic information about the target location was available. We found shorter saccade latencies in the moving compared to the static condition, but no differences in accuracy or precision of saccadic endpoints. In a second experiment, we introduced variable delays after the auditory tone (static condition) or after the end of the hand movement (moving condition) in order to reduce the predictability of the moment of the stimulation and to allow more time to process the kinesthetic information. Again, we found shorter latencies in the moving compared to the static condition but no improvement in saccade accuracy or precision. In a third experiment, we showed that the shorter saccade latencies in the moving condition cannot be explained by the temporal proximity between the relevant event (auditory tone or end of hand movement) and the moment of the stimulation. Our findings suggest that kinesthetic information facilitates planning, but not control, of saccadic eye movements to proprioceptive-tactile targets. Copyright © 2016 Elsevier Ltd. All rights reserved.

Role of peripheral vision in saccade planning: Learning from people with tunnel vision

PubMed Central

Luo, Gang; Vargas-Martin, Fernando; Peli, Eli

2008-01-01

Both visually salient and top-down information are important in eye movement control, but their relative roles in the planning of daily saccades are unclear. We investigated the effect of peripheral vision loss on saccadic behaviors in patients with tunnel vision (visual field diameters 7°–16°) in visual search and real-world walking experiments. The patients made up to two saccades per second to their pre-saccadic blind areas, about half of which had no overlap between the post- and pre-saccadic views. In the visual search experiment, visual field size and the background (blank or picture) did not affect the saccade sizes and direction of patients (n=9). In the walking experiment, the patients (n=5) and normal controls (n=3) had similar distributions of saccade sizes and directions. These findings might provide a clue about the extent of the top-down mechanism influence on eye movement control. PMID:19146326

Saccades to remembered targets: the effects of smooth pursuit and illusory stimulus motion

NASA Technical Reports Server (NTRS)

Zivotofsky, A. Z.; Rottach, K. G.; Averbuch-Heller, L.; Kori, A. A.; Thomas, C. W.; Dell'Osso, L. F.; Leigh, R. J.

1996-01-01

1. Measurements were made in four normal human subjects of the accuracy of saccades to remembered locations of targets that were flashed on a 20 x 30 deg random dot display that was either stationary or moving horizontally and sinusoidally at +/-9 deg at 0.3 Hz. During the interval between the target flash and the memory-guided saccade, the "memory period" (1.4 s), subjects either fixated a stationary spot or pursued a spot moving vertically sinusoidally at +/-9 deg at 0.3 Hz. 2. When saccades were made toward the location of targets previously flashed on a stationary background as subjects fixated the stationary spot, median saccadic error was 0.93 deg horizontally and 1.1 deg vertically. These errors were greater than for saccades to visible targets, which had median values of 0.59 deg horizontally and 0.60 deg vertically. 3. When targets were flashed as subjects smoothly pursued a spot that moved vertically across the stationary background, median saccadic error was 1.1 deg horizontally and 1.2 deg vertically, thus being of similar accuracy to when targets were flashed during fixation. In addition, the vertical component of the memory-guided saccade was much more closely correlated with the "spatial error" than with the "retinal error"; this indicated that, when programming the saccade, the brain had taken into account eye movements that occurred during the memory period. 4. When saccades were made to targets flashed during attempted fixation of a stationary spot on a horizontally moving background, a condition that produces a weak Duncker-type illusion of horizontal movement of the primary target, median saccadic error increased horizontally to 3.2 deg but was 1.1 deg vertically. 5. When targets were flashed as subjects smoothly pursued a spot that moved vertically on the horizontally moving background, a condition that induces a strong illusion of diagonal target motion, median saccadic error was 4.0 deg horizontally and 1.5 deg vertically; thus the horizontal

Eying the future: Eye movement in past and future thinking.

PubMed

El Haj, Mohamad; Lenoble, Quentin

2017-06-07

We investigated eye movement during past and future thinking. Participants were invited to retrieve past events and to imagine future events while their scan path was recorded by an eye-tracker. Past thinking triggered more fixation (p < .05), and saccade counts (p < .05) than future thinking. Past and future thinking triggered a similar duration of fixations and saccades, as well as a similar amplitude of saccades. Interestingly, participants rated past thinking as more vivid than future thinking (p < .01). Therefore, the vividness of past thinking seems to be accompanied by an increased number of fixations and saccades. Fixations and saccades in past thinking can be interpreted as an attempt by the visual system to find (through saccades) and activate (through fixations) stored memory representations. The same interpretation can be applied to future thinking as this ability requires activation of past experiences. However, future thinking triggers fewer fixations and saccades than past thinking: this may be due to its decreased demand on visual imagery, but could also be related to a potentially deleterious effect of eye movements on spatial imagery required for future thinking. Copyright © 2017 Elsevier Ltd. All rights reserved.

Modeling control of eye orientation in three dimensions. I. Role of muscle pulleys in determining saccadic trajectory.

PubMed

Raphan, T

1998-05-01

This study evaluates the effects of muscle axis shifts on the performance of a vector velocity-position integrator in the CNS. Earlier models of the oculomotor plant assumed that the muscle axes remained fixed relative to the head as the eye rotated into secondary and tertiary eye positions. Under this assumption, the vector integrator model generates torsional transients as the eye moves from secondary to tertiary positions of fixation. The torsional transient represents an eye movement response to a spatial mismatch between the torque axes that remain fixed in the head and the displacement plane that changes by half the angle of the change in eye orientation. When muscle axis shifts were incorporated into the model, the torque axes were closer to the displacement plane at each eye orientation throughout the trajectory, and torsional transients were reduced dramatically. Their size and dynamics were close to reported data. It was also shown that when the muscle torque axes were rotated by 50% of the eye rotation, there was no torsional transient and Listing's law was perfectly obeyed. When muscle torque axes rotated >50%, torsional transients reversed direction compared with what occurred for muscle axis shifts of <50%. The model indicates that Listing's law is implemented by the oculomotor plant subject to a two-dimensional command signal that is confined to the pitch-yaw plane, having zero torsion. Saccades that bring the eye to orientations outside Listing's plane could easily be corrected by a roll pulse that resets the roll state of the velocity-position integrator to zero. This would be a simple implementation of the corrective controller suggested by Van Opstal and colleagues. The model further indicates that muscle axis shifts together with the torque orientation relationship for tissue surrounding the eye and Newton's laws of motion form a sufficient plant model to explain saccadic trajectories and periods of fixation when driven by a vector command

A circuit for saccadic suppression in the primate brain

PubMed Central

Cavanaugh, James; McAlonan, Kerry; Wurtz, Robert H.

2017-01-01

Saccades should cause us to see a blur as the eyes sweep across a visual scene. Specific brain mechanisms prevent this by producing suppression during saccades. Neuronal correlates of such suppression were first established in the visual superficial layers of the superior colliculus (SC) and subsequently have been observed in cortical visual areas, including the middle temporal visual area (MT). In this study, we investigated suppression in a recently identified circuit linking visual SC (SCs) to MT through the inferior pulvinar (PI). We examined responses to visual stimuli presented just before saccades to reveal a neuronal correlate of suppression driven by a copy of the saccade command, referred to as a corollary discharge. We found that visual responses were similarly suppressed in SCs, PI, and MT. Within each region, suppression of visual responses occurred with saccades into both visual hemifields, but only in the contralateral hemifield did this suppression consistently begin before the saccade (~100 ms). The consistency of the signal along the circuit led us to hypothesize that the suppression in MT was influenced by input from the SC. We tested this hypothesis in one monkey by inactivating neurons within the SC and found evidence that suppression in MT depends on corollary discharge signals from motor SC (SCi). Combining these results with recent findings in rodents, we propose a complete circuit originating with corollary discharge signals in SCi that produces suppression in visual SCs, PI, and ultimately, MT cortex. NEW & NOTEWORTHY A fundamental puzzle in visual neuroscience is that we frequently make rapid eye movements (saccades) but seldom perceive the visual blur accompanying each movement. We investigated neuronal correlates of this saccadic suppression by recording from and perturbing a recently identified circuit from brainstem to cortex. We found suppression at each stage, with evidence that it was driven by an internally generated signal. We

Saccade-synchronized rapid attention shifts in macaque visual cortical area MT.

PubMed

Yao, Tao; Treue, Stefan; Krishna, B Suresh

2018-03-06

While making saccadic eye-movements to scan a visual scene, humans and monkeys are able to keep track of relevant visual stimuli by maintaining spatial attention on them. This ability requires a shift of attentional modulation from the neuronal population representing the relevant stimulus pre-saccadically to the one representing it post-saccadically. For optimal performance, this trans-saccadic attention shift should be rapid and saccade-synchronized. Whether this is so is not known. We trained two rhesus monkeys to make saccades while maintaining covert attention at a fixed spatial location. We show that the trans-saccadic attention shift in cortical visual medial temporal (MT) area is well synchronized to saccades. Attentional modulation crosses over from the pre-saccadic to the post-saccadic neuronal representation by about 50 ms after a saccade. Taking response latency into account, the trans-saccadic attention shift is well timed to maintain spatial attention on relevant stimuli, so that they can be optimally tracked and processed across saccades.

The saccadic flow baseline: Accounting for image-independent biases in fixation behavior.

PubMed

Clarke, Alasdair D F; Stainer, Matthew J; Tatler, Benjamin W; Hunt, Amelia R

2017-09-01

Much effort has been made to explain eye guidance during natural scene viewing. However, a substantial component of fixation placement appears to be a set of consistent biases in eye movement behavior. We introduce the concept of saccadic flow, a generalization of the central bias that describes the image-independent conditional probability of making a saccade to (xi+1, yi+1), given a fixation at (xi, yi). We suggest that saccadic flow can be a useful prior when carrying out analyses of fixation locations, and can be used as a submodule in models of eye movements during scene viewing. We demonstrate the utility of this idea by presenting bias-weighted gaze landscapes, and show that there is a link between the likelihood of a saccade under the flow model, and the salience of the following fixation. We also present a minor improvement to our central bias model (based on using a multivariate truncated Gaussian), and investigate the leftwards and coarse-to-fine biases in scene viewing.

Electrophysiological recordings in humans reveal reduced location-specific attentional-shift activity prior to recentering saccades

PubMed Central

Boehler, C. Nicolas; Zhang, Helen H.; Schoenfeld, Mircea A.; Woldorff, Marty G.

2012-01-01

Being able to effectively explore the visual world is of fundamental importance, and it has been suggested that the straight-ahead gaze position within the egocentric reference frame (“primary position”) might play a special role in this context. In the present study we employed human electroencephalography (EEG) to examine neural activity related to the spatial guidance of saccadic eye movements. Moreover, we sought to investigate whether such activity would be modulated by the spatial relation of saccade direction to the primary gaze position (recentering saccades). Participants executed endogenously cued saccades between five equidistant locations along the horizontal meridian. This design allowed for the comparison of isoamplitude saccades from the same starting position that were oriented either toward the primary position (centripetal) or further away from it (centrifugal). By back-averaging time-locked to the saccade onset on each trial, we identified a parietally distributed, negative-polarity EEG deflection contralateral to the direction of the upcoming saccade. Importantly, this contralateral presaccadic negativity, which appeared to reflect the location-specific attentional guidance of the eye movement, was attenuated for recentering saccades relative to isoamplitude centrifugal saccades. This differential electrophysiological signature was paralleled by faster saccadic reaction times and was substantially more apparent when time-locking the data to the onset of the saccade rather than to the onset of the cue, suggesting a tight temporal association with saccade initiation. The diminished level of this presaccadic component for recentering saccades may reflect the preferential coding of the straight-ahead gaze position, in which both the eye-centered and head-centered reference frames are perfectly aligned and from which the visual world can be effectively explored. PMID:22157127

The role of peripheral vision in saccade planning: learning from people with tunnel vision.

PubMed

Luo, Gang; Vargas-Martin, Fernando; Peli, Eli

2008-12-22

Both visually salient and top-down information are important in eye movement control, but their relative roles in the planning of daily saccades are unclear. We investigated the effect of peripheral vision loss on saccadic behaviors in patients with tunnel vision (visual field diameters 7 degrees-16 degrees) in visual search and real-world walking experiments. The patients made up to two saccades per second to their pre-saccadic blind areas, about half of which had no overlap between the post- and pre-saccadic views. In the visual search experiment, visual field size and the background (blank or picture) did not affect the saccade sizes and direction of patients (n = 9). In the walking experiment, the patients (n = 5) and normal controls (n = 3) had similar distributions of saccade sizes and directions. These findings might provide a clue about the large extent of the top-down mechanism influence on eye movement control.

Are Covert Saccade Functionally Relevant in Vestibular Hypofunction?

PubMed

Hermann, R; Pelisson, D; Dumas, O; Urquizar, Ch; Truy, E; Tilikete, C

2018-06-01

The vestibulo-ocular reflex maintains gaze stabilization during angular or linear head accelerations, allowing adequate dynamic visual acuity. In case of bilateral vestibular hypofunction, patients use saccades to compensate for the reduced vestibulo-ocular reflex function, with covert saccades occurring even during the head displacement. In this study, we questioned whether covert saccades help maintain dynamic visual acuity, and evaluated which characteristic of these saccades are the most relevant to improve visual function. We prospectively included 18 patients with chronic bilateral vestibular hypofunction. Subjects underwent evaluation of dynamic visual acuity in the horizontal plane as well as video recording of their head and eye positions during horizontal head impulse tests in both directions (36 ears tested). Frequency, latency, consistency of covert saccade initiation, and gain of covert saccades as well as residual vestibulo-ocular reflex gain were calculated. We found no correlation between residual vestibulo-ocular reflex gain and dynamic visual acuity. Dynamic visual acuity performance was however positively correlated with the frequency and gain of covert saccades and negatively correlated with covert saccade latency. There was no correlation between consistency of covert saccade initiation and dynamic visual acuity. Even though gaze stabilization in space during covert saccades might be of very short duration, these refixation saccades seem to improve vision in patients with bilateral vestibular hypofunction during angular head impulses. These findings emphasize the need for specific rehabilitation technics that favor the triggering of covert saccades. The physiological origin of covert saccades is discussed.

Smooth Pursuit Saccade Amplitude Modulation During Exposure to Microgravity

NASA Technical Reports Server (NTRS)

Reschke, M. F.; Kozlovskaya, I. B.; Sayenko, D. G.; Sayenko, I.; Somers, J. T.; Paloski, W. H.

2002-01-01

Russian investigators have reported changes in pursuit tracking of a vertically moving point stimulus during space flight. Early in microgravity, changes were manifested by decreased eye movement amplitude (undershooting) and the appearance of correction saccades. As the flight progressed, pursuit of the moving point stimulus deteriorated while associated saccadic movements were unchanged. Immediately postflight there was an improved execution of active head movements indicating that the deficiencies in pursuit function noted in microgravity may be of central origin. In contrast, tests of two cosmonauts showed that horizontal and vertical smooth pursuit were unchanged inflight. However, results of corresponding saccadic tasks showed a tendency toward the overshooting of a horizontal target early inflight with high accuracy developing later inflight, accompanied by an increased saccade velocity and a trend toward decreased saccade latency. Based on these equivocal results, we have further investigated the effects of space flight on the smooth pursuit mechanism during and after short duration flight, and postflight on returning MIR crewmembers. Sinusoidal target movement was presented horizontally at frequencies of 0.33 and 1.0 Hz. Subjects were asked to perform two trials for each stimulus combination: (1) moving eyes-only (EO) and (2) moving eyes and head (EH) with the target motion. Peak amplitude was 30 deg for 0.33 Hz trials and 15 deg for the 1.0 Hz trials. The relationship between saccade amplitude and peak velocity were plotted as a main sequence for each phase of flight, and linear regression analysis allowed us to determine the slope of each main sequence plot. The linear slopes were then combined for each flight phase for each individual subject. The main sequence for both EO and EH trials at both the 0.33 and 1.0 Hz frequencies during flight for the short duration flyers showed a reduction in saccade velocity and amplitude when compared to the preflight

Choice of saccade endpoint under risk

PubMed Central

Ackermann, John F.; Landy, Michael S.

2013-01-01

Eye movements function to bring detailed information onto the high-resolution region of the retina. Previous research has shown that human observers select fixation points that maximize information acquisition and minimize target location uncertainty. In this study, we ask whether human observers choose the saccade endpoint that maximizes gain when there are explicit rewards associated with correctly detecting the target. Observers performed an 8-alternative forced-choice detection task for a contrast-defined target in noise. After a single saccade, observers indicated the target location. Each potential target location had an associated reward that was known to the observer. In some conditions, the reward at one location was higher than at the other locations. We compared human saccade endpoints to those of an ideal observer that maximizes expected gain given the respective human observer's visibility map, i.e., d′ for target detection as a function of retinal location. Varying the location of the highest reward had a significant effect on human observers' distribution of saccade endpoints. Both human and ideal observers show a high density of saccades made toward the highest rewarded and actual target locations. But humans' overall spatial distributions of saccade endpoints differed significantly from the ideal observer as they made a greater number of saccade to locations far from the highest rewarded and actual target locations. Suboptimal choice of saccade endpoint, possibly in combination with suboptimal integration of information across saccades, had a significant effect on human observers' ability to correctly detect the target and maximize gain. PMID:24023277

Eye Movement Indices in the Study of Depressive Disorder.

PubMed

Li, Yu; Xu, Yangyang; Xia, Mengqing; Zhang, Tianhong; Wang, Junjie; Liu, Xu; He, Yongguang; Wang, Jijun

2016-12-25

Impaired cognition is one of the most common core symptoms of depressive disorder. Eye movement testing mainly reflects patients' cognitive functions, such as cognition, memory, attention, recognition, and recall. This type of testing has great potential to improve theories related to cognitive functioning in depressive episodes as well as potential in its clinical application. This study investigated whether eye movement indices of patients with unmedicated depressive disorder were abnormal or not, as well as the relationship between these indices and mental symptoms. Sixty patients with depressive disorder and sixty healthy controls (who were matched by gender, age and years of education) were recruited, and completed eye movement tests including three tasks: fixation task, saccade task and free-view task. The EyeLink desktop eye tracking system was employed to collect eye movement information, and analyze the eye movement indices of the three tasks between the two groups. (1) In the fixation task, compared to healthy controls, patients with depressive disorder showed more fixations, shorter fixation durations, more saccades and longer saccadic lengths; (2) In the saccade task, patients with depressive disorder showed longer anti-saccade latencies and smaller anti-saccade peak velocities; (3) In the free-view task, patients with depressive disorder showed fewer saccades and longer mean fixation durations; (4) Correlation analysis showed that there was a negative correlation between the pro-saccade amplitude and anxiety symptoms, and a positive correlation between the anti-saccade latency and anxiety symptoms. The depression symptoms were negatively correlated with fixation times, saccades, and saccadic paths respectively in the free-view task; while the mean fixation duration and depression symptoms showed a positive correlation. Compared to healthy controls, patients with depressive disorder showed significantly abnormal eye movement indices. In addition

Curved Saccade Trajectories Reveal Conflicting Predictions in Associative Learning

ERIC Educational Resources Information Center

Koenig, Stephan; Lachnit, Harald

2011-01-01

We report how the trajectories of saccadic eye movements are affected by memory interference acquired during associative learning. Human participants learned to perform saccadic choice responses based on the presentation of arbitrary central cues A, B, AC, BC, AX, BY, X, and Y that were trained to predict the appearance of a peripheral target…

Effects of Reduced Acuity and Stereo Acuity on Saccades and Reaching Movements in Adults With Amblyopia and Strabismus.

PubMed

Niechwiej-Szwedo, Ewa; Goltz, Herbert C; Colpa, Linda; Chandrakumar, Manokaraananthan; Wong, Agnes M F

2017-02-01

Our previous work has shown that amblyopia disrupts the planning and execution of visually-guided saccadic and reaching movements. We investigated the association between the clinical features of amblyopia and aspects of visuomotor behavior that are disrupted by amblyopia. A total of 55 adults with amblyopia (22 anisometropic, 18 strabismic, 15 mixed mechanism), 14 adults with strabismus without amblyopia, and 22 visually-normal control participants completed a visuomotor task while their eye and hand movements were recorded. Univariate and multivariate analyses were performed to assess the association between three clinical predictors of amblyopia (amblyopic eye [AE] acuity, stereo sensitivity, and eye deviation) and seven kinematic outcomes, including saccadic and reach latency, interocular saccadic and reach latency difference, saccadic and reach precision, and PA/We ratio (an index of reach control strategy efficacy using online feedback correction). Amblyopic eye acuity explained 28% of the variance in saccadic latency, and 48% of the variance in mean saccadic latency difference between the amblyopic and fellow eyes (i.e., interocular latency difference). In contrast, for reach latency, AE acuity explained only 10% of the variance. Amblyopic eye acuity was associated with reduced endpoint saccadic (23% of variance) and reach (22% of variance) precision in the amblyopic group. In the strabismus without amblyopia group, stereo sensitivity and eye deviation did not explain any significant variance in saccadic and reach latency or precision. Stereo sensitivity was the best clinical predictor of deficits in reach control strategy, explaining 23% of total variance of PA/We ratio in the amblyopic group and 12% of variance in the strabismus without amblyopia group when viewing with the amblyopic/nondominant eye. Deficits in eye and limb movement initiation (latency) and target localization (precision) were associated with amblyopic acuity deficit, whereas changes in

The effect of sampling rate and lowpass filters on saccades - A modeling approach.

PubMed

Mack, David J; Belfanti, Sandro; Schwarz, Urs

2017-12-01

The study of eye movements has become popular in many fields of science. However, using the preprocessed output of an eye tracker without scrutiny can lead to low-quality or even erroneous data. For example, the sampling rate of the eye tracker influences saccadic peak velocity, while inadequate filters fail to suppress noise or introduce artifacts. Despite previously published guiding values, most filter choices still seem motivated by a trial-and-error approach, and a thorough analysis of filter effects is missing. Therefore, we developed a simple and easy-to-use saccade model that incorporates measured amplitude-velocity main sequences and produces saccades with a similar frequency content to real saccades. We also derived a velocity divergence measure to rate deviations between velocity profiles. In total, we simulated 155 saccades ranging from 0.5° to 60° and subjected them to different sampling rates, noise compositions, and various filter settings. The final goal was to compile a list with the best filter settings for each of these conditions. Replicating previous findings, we observed reduced peak velocities at lower sampling rates. However, this effect was highly non-linear over amplitudes and increasingly stronger for smaller saccades. Interpolating the data to a higher sampling rate significantly reduced this effect. We hope that our model and the velocity divergence measure will be used to provide a quickly accessible ground truth without the need for recording and manually labeling saccades. The comprehensive list of filters allows one to choose the correct filter for analyzing saccade data without resorting to trial-and-error methods.

Cortical functional anatomy of voluntary saccades in Parkinson disease.

PubMed

Rieger, Jochem W; Kim, Aleander; Argyelan, Miklos; Farber, Mark; Glazman, Sofya; Liebeskind, Marc; Meyer, Thomas; Bodis-Wollner, Ivan

2008-10-01

In Parkinson Disease (PD) several aspects of saccades are affected. The saccade-generating brainstem neurons are spared, however, the signals they receive may be flawed. In particular voluntary saccades suffer, but the functional anatomy of the impairment of saccade-related cortical control is unknown. We measured blood-oxygenation-level-dependent (BOLD) activation with functional Magnetic Resonance Imaging (fMRI) while healthy participants and patients with PD performed horizontal voluntary saccades between peripheral visual targets or fixated centrally. We compared saccade-related BOLD-activity vs. fixation in patients with PD and in healthy controls and correlated perisaccadic BOLD-activity in PD patients with saccade kinetics (multistep saccades). Saccade related BOLD-activation was found in both PD and healthy participants in the superior parietal cortex (PEF) and the occipital cortex. Our results suggest remarkable hypoactivity of the frontal and supplementary eye fields (FEF and SEF) in PD patients. On the other hand, PD patients showed a statistically more reliable BOLD modulation than healthy participants in the posterior cingulate gyrus, the parahippocampal gyrus, inferior parietal lobule, precuneus and in the middle temporal gyrus. Given abnormal frontal and normal PEF responses, our results suggest that in PD a frontal cortical circuitry, known to be associated with saccade planning, selection, and predicting a metric error of the saccade, is deficient.

Lack of oblique astigmatism in the chicken eye.

PubMed

Maier, Felix M; Howland, Howard C; Ohlendorf, Arne; Wahl, Siegfried; Schaeffel, Frank

2015-04-01

Primate eyes display considerable oblique off-axis astigmatism which could provide information on the sign of defocus that is needed for emmetropization. The pattern of peripheral astigmatism is not known in the chicken eye, a common model of myopia. Peripheral astigmatism was mapped out over the horizontal visual field in three chickens, 43 days old, and in three near emmetropic human subjects, average age 34.7years, using infrared photoretinoscopy. There were no differences in astigmatism between humans and chickens in the central visual field (chicks -0.35D, humans -0.65D, n.s.) but large differences in the periphery (i.e. astigmatism at 40° in the temporal visual field: humans -4.21D, chicks -0.63D, p<0.001, unpaired t-test). The lack of peripheral astigmatism in chicks was not due to differences in corneal shape. Perhaps related to their superior peripheral optics, we found that chickens had excellent visual performance also in the far periphery. Using an automated optokinetic nystagmus paradigm, no difference was observed in spatial visual performance with vision restricted to either the central 67° of the visual field or to the periphery beyond 67°. Accommodation was elicited by stimuli presented far out in the visual field. Transscleral images of single infrared LEDs showed no sign of peripheral astigmatism. The chick may be the first terrestrial vertebrate described to lack oblique astigmatism. Since corneal shape cannot account for the difference in astigmatism in humans and chicks, it must trace back to the design of the crystalline lens. The lack of peripheral astigmatism in chicks also excludes a role in emmetropization. Copyright © 2015 Elsevier Ltd. All rights reserved.

Evidence against the facilitation of the vergence command during saccade-vergence interactions.

PubMed

Hendel, Tal; Gur, Moshe

2012-11-01

Combined saccade-vergence movements result when gaze shifts are made to targets that differ both in direction and in depth from the momentary fixation point. Currently, there are two rivaling schemes to explain these eye movements. According to the first, such eye movements are due to a combination of a conjugate saccadic command and a symmetric vergence command; the two commands are not taken to be independent but instead are suggested to interact in a nonlinear manner, which leads to an intra-saccadic facilitation of the vergence command. According to the second scheme, the saccade generator is disconjugate, thus encoding vergence information in the saccadic commands themselves, and the remaining vergence requirement is provided by an asymmetric mechanism. Here, we test the scheme that suggests an intra-saccadic facilitation of the vergence command. We analyze this scheme and show that it has two fundamental properties. The first is that the vergence command is always symmetric, even during the intra-saccadic facilitation. The second is that the facilitated (and symmetric) vergence command sums linearly with the conjugate saccadic command at the final common pathway. Taking these properties together, this scheme predicts that the total magnitude of the saccadic component of combined saccade-vergence movements can be decomposed into a conjugate part and a symmetric part. When we tested this prediction in combined saccade-vergence movements of humans, we found that it was not confirmed. Thus, our results are incompatible with the facilitation of the vergence command hypothesis. Although these results do not directly verify the rivaling hypothesis, which suggests a disconjugate saccade generator, they do provide it with indirect support.

The effects of video game play on the characteristics of saccadic eye movements.

PubMed

Mack, David J; Ilg, Uwe J

2014-09-01

Video game play has become a common leisure activity all around the world. To reveal possible effects of playing video games, we measured saccades elicited by video game players (VGPs) and non-players (NVGPs) in two oculomotor tasks. First, our subjects performed a double-step task. Second, we asked our subjects to move their gaze opposite to the appearance of a visual target, i.e. to perform anti-saccades. As expected on the basis of previous studies, VGPs had significantly shorter saccadic reaction times (SRTs) than NVGPs for all saccade types. However, the error rates in the anti-saccade task did not reveal any significant differences. In fact, the error rates of VGPs were actually slightly lower compared to NVGPs (34% versus 40%, respectively). In addition, VGPs showed significantly higher saccadic peak velocities in every saccade type compared to NVGP. Our results suggest that faster SRTs in VGPs were associated with a more efficient motor drive for saccades. Taken together, our results are in excellent agreement with earlier reports of beneficial video game effects through the general reduction in SRTs. Our data clearly provides additional experimental evidence for an higher efficiency of the VGPs on the one hand and refutes the notion of a reduced impulse control in VGPs on the other. Copyright © 2014 Elsevier Ltd. All rights reserved.

Between-object and within-object saccade programming in a visual search task.

PubMed

Vergilino-Perez, Dorine; Findlay, John M

2006-07-01

The role of the perceptual organization of the visual display on eye movement control was examined in two experiments using a task where a two-saccade sequence was directed toward either a single elongated object or three separate shorter objects. In the first experiment, we examined the consequences for the second saccade of a small displacement of the whole display during the first saccade. We found that between-object saccades compensated for the displacement to aim for a target position on the new object whereas within-object saccades did not show compensation but were coded as a fixed motor vector applied irrespective of wherever the preceding saccade landed. In the second experiment, we extended the paradigm to examine saccades performed in different directions. The results suggest that the within-object and between-object saccade distinction is an essential feature of saccadic planning.

Gravity modulates Listing's plane orientation during both pursuit and saccades

NASA Technical Reports Server (NTRS)

Hess, Bernhard J M.; Angelaki, Dora E.

2003-01-01

Previous studies have shown that the spatial organization of all eye orientations during visually guided saccadic eye movements (Listing's plane) varies systematically as a function of static and dynamic head orientation in space. Here we tested if a similar organization also applies to the spatial orientation of eye positions during smooth pursuit eye movements. Specifically, we characterized the three-dimensional distribution of eye positions during horizontal and vertical pursuit (0.1 Hz, +/-15 degrees and 0.5 Hz, +/-8 degrees) at different eccentricities and elevations while rhesus monkeys were sitting upright or being statically tilted in different roll and pitch positions. We found that the spatial organization of eye positions during smooth pursuit depends on static orientation in space, similarly as during visually guided saccades and fixations. In support of recent modeling studies, these results are consistent with a role of gravity on defining the parameters of Listing's law.

Decoding Saccadic Directions Using Epidural ECoG in Non-Human Primates

PubMed Central

2017-01-01

A brain-computer interface (BCI) can be used to restore some communication as an alternative interface for patients suffering from locked-in syndrome. However, most BCI systems are based on SSVEP, P300, or motor imagery, and a diversity of BCI protocols would be needed for various types of patients. In this paper, we trained the choice saccade (CS) task in 2 non-human primate monkeys and recorded the brain signal using an epidural electrocorticogram (eECoG) to predict eye movement direction. We successfully predicted the direction of the upcoming eye movement using a support vector machine (SVM) with the brain signals after the directional cue onset and before the saccade execution. The mean accuracies were 80% for 2 directions and 43% for 4 directions. We also quantified the spatial-spectro-temporal contribution ratio using SVM recursive feature elimination (RFE). The channels over the frontal eye field (FEF), supplementary eye field (SEF), and superior parietal lobule (SPL) area were dominantly used for classification. The α-band in the spectral domain and the time bins just after the directional cue onset and just before the saccadic execution were mainly useful for prediction. A saccade based BCI paradigm can be projected in the 2D space, and will hopefully provide an intuitive and convenient communication platform for users. PMID:28665058

Decoding Saccadic Directions Using Epidural ECoG in Non-Human Primates.

PubMed

Lee, Jeyeon; Choi, Hoseok; Lee, Seho; Cho, Baek Hwan; Ahn, Kyoung Ha; Kim, In Young; Lee, Kyoung Min; Jang, Dong Pyo

2017-08-01

A brain-computer interface (BCI) can be used to restore some communication as an alternative interface for patients suffering from locked-in syndrome. However, most BCI systems are based on SSVEP, P300, or motor imagery, and a diversity of BCI protocols would be needed for various types of patients. In this paper, we trained the choice saccade (CS) task in 2 non-human primate monkeys and recorded the brain signal using an epidural electrocorticogram (eECoG) to predict eye movement direction. We successfully predicted the direction of the upcoming eye movement using a support vector machine (SVM) with the brain signals after the directional cue onset and before the saccade execution. The mean accuracies were 80% for 2 directions and 43% for 4 directions. We also quantified the spatial-spectro-temporal contribution ratio using SVM recursive feature elimination (RFE). The channels over the frontal eye field (FEF), supplementary eye field (SEF), and superior parietal lobule (SPL) area were dominantly used for classification. The α-band in the spectral domain and the time bins just after the directional cue onset and just before the saccadic execution were mainly useful for prediction. A saccade based BCI paradigm can be projected in the 2D space, and will hopefully provide an intuitive and convenient communication platform for users. © 2017 The Korean Academy of Medical Sciences.

Paying attention to saccadic intrusions.

PubMed

Gowen, E; Abadi, R V; Poliakoff, E

2005-12-01

Fixation to a target in primary gaze is invariably interrupted by physiological conjugate saccadic intrusions (SI). These small idiosyncratic eye movements (usually <1 degrees in amplitude) take the form of an initial horizontal fast eye movement away from the desired eye position, followed after a variable duration by a return saccade or drift. As the aetiology of SI is still unclear, it was the aim of this study to investigate whether SI are related to exogenous or endogenous attentional processes. This was achieved by varying (a) the "bottom-up" target viewing conditions (target presence, servo control of the target, target background, target size) and (b) the 'top-down' attentional state (instruction change--'look' or 'hold eyes steady' and passive fixation versus active--'respond to change' fixation) in 13 subjects (the number of participants in each task varied between 7 and 11). We also manipulated the orientation of pure exogenous attention through a cue-target task, during which subjects were required to respond to a target, preceded by a non-informative cue by either pressing a button or making a saccade towards the target. SI amplitude, duration, frequency and direction were measured. SI amplitude was found to be significantly higher when the target was absent and SI frequency significantly lower during open loop conditions. Target size and background influenced SI behaviour in an idiosyncratic manner, although there was a trend for subjects to exhibit lower SI frequencies and amplitudes when a patterned background was present and larger SI amplitudes with larger target sizes. SI frequency decreased during the "hold eyes steady" passive command as well as during active fixation but SI direction was not influenced by the exogenous cue-target task. These results suggest that SI are related to endogenous rather than exogenous attention mechanisms. Our experiments lead us to propose that SI represent shifts in endogenous attention that reflect a baseline

Reading "sun" and looking up: the influence of language on saccadic eye movements in the vertical dimension.

PubMed

Dudschig, Carolin; Souman, Jan; Lachmair, Martin; de la Vega, Irmgard; Kaup, Barbara

2013-01-01

Traditionally, language processing has been attributed to a separate system in the brain, which supposedly works in an abstract propositional manner. However, there is increasing evidence suggesting that language processing is strongly interrelated with sensorimotor processing. Evidence for such an interrelation is typically drawn from interactions between language and perception or action. In the current study, the effect of words that refer to entities in the world with a typical location (e.g., sun, worm) on the planning of saccadic eye movements was investigated. Participants had to perform a lexical decision task on visually presented words and non-words. They responded by moving their eyes to a target in an upper (lower) screen position for a word (non-word) or vice versa. Eye movements were faster to locations compatible with the word's referent in the real world. These results provide evidence for the importance of linguistic stimuli in directing eye movements, even if the words do not directly transfer directional information.

Effects of spatial congruency on saccade and visual discrimination performance in a dual-task paradigm.

PubMed

Moehler, Tobias; Fiehler, Katja

2014-12-01

The present study investigated the coupling of selection-for-perception and selection-for-action during saccadic eye movement planning in three dual-task experiments. We focused on the effects of spatial congruency of saccade target (ST) location and discrimination target (DT) location and the time between ST-cue and Go-signal (SOA) on saccadic eye movement performance. In two experiments, participants performed a visual discrimination task at a cued location while programming a saccadic eye movement to a cued location. In the third experiment, the discrimination task was not cued and appeared at a random location. Spatial congruency of ST-location and DT-location resulted in enhanced perceptual performance irrespective of SOA. Perceptual performance in spatially incongruent trials was above chance, but only when the DT-location was cued. Saccade accuracy and precision were also affected by spatial congruency showing superior performance when the ST- and DT-location coincided. Saccade latency was only affected by spatial congruency when the DT-cue was predictive of the ST-location. Moreover, saccades consistently curved away from the incongruent DT-locations. Importantly, the effects of spatial congruency on saccade parameters only occurred when the DT-location was cued; therefore, results from experiments 1 and 2 are due to the endogenous allocation of attention to the DT-location and not caused by the salience of the probe. The SOA affected saccade latency showing decreasing latencies with increasing SOA. In conclusion, our results demonstrate that visuospatial attention can be voluntarily distributed upon spatially distinct perceptual and motor goals in dual-task situations, resulting in a decline of visual discrimination and saccade performance.

Eye Movement Indices in the Study of Depressive Disorder

PubMed Central

LI, Yu; XU, Yangyang; XIA, Mengqing; ZHANG, Tianhong; WANG, Junjie; LIU, Xu; HE, Yongguang; WANG, Jijun

2016-01-01

Background Impaired cognition is one of the most common core symptoms of depressive disorder. Eye movement testing mainly reflects patients’ cognitive functions, such as cognition, memory, attention, recognition, and recall. This type of testing has great potential to improve theories related to cognitive functioning in depressive episodes as well as potential in its clinical application. Aims This study investigated whether eye movement indices of patients with unmedicated depressive disorder were abnormal or not, as well as the relationship between these indices and mental symptoms. Methods Sixty patients with depressive disorder and sixty healthy controls (who were matched by gender, age and years of education) were recruited, and completed eye movement tests including three tasks: fixation task, saccade task and free-view task. The EyeLink desktop eye tracking system was employed to collect eye movement information, and analyze the eye movement indices of the three tasks between the two groups. Results (1) In the fixation task, compared to healthy controls, patients with depressive disorder showed more fixations, shorter fixation durations, more saccades and longer saccadic lengths; (2) In the saccade task, patients with depressive disorder showed longer anti-saccade latencies and smaller anti-saccade peak velocities; (3) In the free-view task, patients with depressive disorder showed fewer saccades and longer mean fixation durations; (4) Correlation analysis showed that there was a negative correlation between the pro-saccade amplitude and anxiety symptoms, and a positive correlation between the anti-saccade latency and anxiety symptoms. The depression symptoms were negatively correlated with fixation times, saccades, and saccadic paths respectively in the free-view task; while the mean fixation duration and depression symptoms showed a positive correlation. Conclusion Compared to healthy controls, patients with depressive disorder showed significantly

Breaking object correspondence across saccades impairs object recognition: The role of color and luminance.

PubMed

Poth, Christian H; Schneider, Werner X

2016-09-01

Rapid saccadic eye movements bring the foveal region of the eye's retina onto objects for high-acuity vision. Saccades change the location and resolution of objects' retinal images. To perceive objects as visually stable across saccades, correspondence between the objects before and after the saccade must be established. We have previously shown that breaking object correspondence across the saccade causes a decrement in object recognition (Poth, Herwig, & Schneider, 2015). Color and luminance can establish object correspondence, but it is unknown how these surface features contribute to transsaccadic visual processing. Here, we investigated whether changing the surface features color-and-luminance and color alone across saccades impairs postsaccadic object recognition. Participants made saccades to peripheral objects, which either maintained or changed their surface features across the saccade. After the saccade, participants briefly viewed a letter within the saccade target object (terminated by a pattern mask). Postsaccadic object recognition was assessed as participants' accuracy in reporting the letter. Experiment A used the colors green and red with different luminances as surface features, Experiment B blue and yellow with approximately the same luminances. Changing the surface features across the saccade deteriorated postsaccadic object recognition in both experiments. These findings reveal a link between object recognition and object correspondence relying on the surface features colors and luminance, which is currently not addressed in theories of transsaccadic perception. We interpret the findings within a recent theory ascribing this link to visual attention (Schneider, 2013).

Parietal and superior frontal visuospatial maps activated by pointing and saccades

PubMed Central

Hagler, D.J.; Riecke, L.; Sereno, M.I.

2009-01-01

A recent study from our laboratory demonstrated that parietal cortex contains a map of visual space related to saccades and spatial attention and identified this area as the likely human homologue of the lateral intraparietal (LIP). A human homologue for the parietal reach region (PRR), thought to preferentially encode planned hand movements, has also been recently proposed. Both of these areas, originally identified in the macaque monkey, have been shown to encode space with eye-centered coordinates. Functional magnetic resonance imaging (fMRI) of humans was used to test the hypothesis that the putative human PRR contains a retinotopic map recruited by finger pointing but not saccades and to test more generally for differences in the visuospatial maps recruited by pointing and saccades. We identified multiple maps in both posterior parietal cortex and superior frontal cortex recruited for eye and hand movements, including maps not observed in previous mapping studies. Pointing and saccade maps were generally consistent within single subjects. We have developed new group analysis methods for phase-encoded data, which revealed subtle differences between pointing and saccades, including hemispheric asymmetries, but we did not find evidence of pointing-specific maps of visual space. PMID:17376706

Effect of pharmacological inactivation of nucleus reticularis tegmenti pontis on saccadic eye movements in the monkey.

PubMed

Kaneko, Chris R S; Fuchs, Albert F

2006-06-01

The superior colliculus (SC) provides signals for the generation of saccades via a direct pathway to the brain stem burst generator (BG). In addition, it sends saccade-related activity to the BG indirectly through the cerebellum via a relay in the nucleus reticularis tegmenti pontis (NRTP). Lesions of the oculomotor vermis, lobules VIc and VII, and inactivation of the caudal fastigial nucleus, the cerebellar output nucleus to which it projects, produce saccade dysmetria but have little effect on saccade peak velocity and duration. We expected similar deficits from inactivation of the NRTP. Instead, injections as small as 80 nl into the NRTP first slowed ipsiversive saccades and then gradually reduced their amplitudes. Postinjection saccades had slower peak velocities and longer durations than preinjection saccades with similar amplitudes. Contraversive saccades retained their normal kinematics. When the gains of ipsiversive saccades to 10 degrees target steps had fallen to their lowest values (0.28 +/- 0.19; mean +/- SD; n = 10 experiments), the gains of contraversive saccades to 10 degrees target steps had decreased very little (0.82 +/- 0.11). Eventually, ipsiversive saccades did not exceed 5 degrees , even to 20 degrees target steps. Moreover, these small remaining saccades apparently were made with considerable difficulty because their latencies increased substantially. When ipsiversive saccade gain was at its lowest, the gain and kinematics of vertical saccades to 10 degrees target steps exhibited inconsistent changes. We argue that our injections did not compromise the direct SC pathway. Therefore these data suggest that the cerebellar saccade pathway does not simply modulate BG activity but is required for horizontal saccades to occur at all.

Effect of Pharmacological Inactivation of Nucleus Reticularis Tegmenti Pontis on Saccadic Eye Movements in the Monkey

PubMed Central

Kaneko, Chris R. S.; Fuchs, Albert F.

2006-01-01

The superior colliculus (SC) provides signals for the generation of saccades via a direct pathway to the brain stem burst generator (BG). In addition, it sends saccade-related activity to the BG indirectly through the cerebellum via a relay in the nucleus reticularis tegmenti pontis (NRTP). Lesions of the oculomotor vermis, lobules VIc and VII, and inactivation of the caudal fastigial nucleus, the cerebellar output nucleus to which it projects, produce saccade dysmetria but have little effect on saccade peak velocity and duration. We expected similar deficits from inactivation of the NRTP. Instead, injections as small as 80 nl into the NRTP first slowed ipsiversive saccades and then gradually reduced their amplitudes. Postinjection saccades had slower peak velocities and longer durations than preinjection saccades with similar amplitudes. Contraversive saccades retained their normal kinematics. When the gains of ipsiversive saccades to 10° target steps had fallen to their lowest values (0.28 ± 0.19; mean ± SD; n = 10 experiments), the gains of contraversive saccades to 10° target steps had decreased very little (0.82 ± 0.11). Eventually, ipsiversive saccades did not exceed 5°, even to 20° target steps. Moreover, these small remaining saccades apparently were made with considerable difficulty because their latencies increased substantially. When ipsiversive saccade gain was at its lowest, the gain and kinematics of vertical saccades to 10° target steps exhibited inconsistent changes. We argue that our injections did not compromise the direct SC pathway. Therefore these data suggest that the cerebellar saccade pathway does not simply modulate BG activity but is required for horizontal saccades to occur at all. PMID:16467420

Neurones associated with saccade metrics in the monkey central mesencephalic reticular formation

PubMed Central

Cromer, Jason A; Waitzman, David M

2006-01-01

Neurones in the central mesencephalic reticular formation (cMRF) begin to discharge prior to saccades. These long lead burst neurones interact with major oculomotor centres including the superior colliculus (SC) and the paramedian pontine reticular formation (PPRF). Three different functions have been proposed for neurones in the cMRF: (1) to carry eye velocity signals that provide efference copy information to the SC (feedback), (2) to provide duration signals from the omnipause neurones to the SC (feedback), or (3) to participate in the transformation from the spatial encoding of a target selection signal in the SC into the temporal pattern of discharge used to drive the excitatory burst neurones in the pons (feed-forward). According to each respective proposal, specific predictions about cMRF neuronal discharge have been formulated. Individual neurones should: (1) encode instantaneous eye velocity, (2) burst specifically in relation to saccade duration but not to other saccade metrics, or (3) have a spectrum of weak to strong correlations to saccade dynamics. To determine if cMRF neurones could subserve these multiple oculomotor roles, we examined neuronal activity in relation to a variety of saccade metrics including amplitude, velocity and duration. We found separate groups of cMRF neurones that have the characteristics predicted by each of the proposed models. We also identified a number of subgroups for which no specific model prediction had previously been established. We found that we could accurately predict the neuronal firing pattern during one type of saccade behaviour (visually guided) using the activity during an alternative behaviour with different saccade metrics (memory guided saccades). We suggest that this evidence of a close relationship of cMRF neuronal discharge to individual saccade metrics supports the hypothesis that the cMRF participates in multiple saccade control pathways carrying saccade amplitude, velocity and duration information

Looking away from faces: influence of high-level visual processes on saccade programming.

PubMed

Morand, Stéphanie M; Grosbras, Marie-Hélène; Caldara, Roberto; Harvey, Monika

2010-03-30

Human faces capture attention more than other visual stimuli. Here we investigated whether such face-specific biases rely on automatic (involuntary) or voluntary orienting responses. To this end, we used an anti-saccade paradigm, which requires the ability to inhibit a reflexive automatic response and to generate a voluntary saccade in the opposite direction of the stimulus. To control for potential low-level confounds in the eye-movement data, we manipulated the high-level visual properties of the stimuli while normalizing their global low-level visual properties. Eye movements were recorded in 21 participants who performed either pro- or anti-saccades to a face, car, or noise pattern, randomly presented to the left or right of a fixation point. For each trial, a symbolic cue instructed the observer to generate either a pro-saccade or an anti-saccade. We report a significant increase in anti-saccade error rates for faces compared to cars and noise patterns, as well as faster pro-saccades to faces and cars in comparison to noise patterns. These results indicate that human faces induce stronger involuntary orienting responses than other visual objects, i.e., responses that are beyond the control of the observer. Importantly, this involuntary processing cannot be accounted for by global low-level visual factors.

Influence of environmental statistics on inhibition of saccadic return

PubMed Central

Farrell, Simon; Ludwig, Casimir J. H.; Ellis, Lucy A.; Gilchrist, Iain D.

2009-01-01

Initiating an eye movement is slowed if the saccade is directed to a location that has been fixated in the recent past. We show that this inhibitory effect is modulated by the temporal statistics of the environment: If a return location is likely to become behaviorally relevant, inhibition of return is absent. By fitting an accumulator model of saccadic decision-making, we show that the inhibitory effect and the sensitivity to local statistics can be dissociated in their effects on the rate of accumulation of evidence, and the threshold controlling the amount of evidence needed to generate a saccade. PMID:20080778

Abnormalities of fixation, saccade and pursuit in posterior cortical atrophy.

PubMed

Shakespeare, Timothy J; Kaski, Diego; Yong, Keir X X; Paterson, Ross W; Slattery, Catherine F; Ryan, Natalie S; Schott, Jonathan M; Crutch, Sebastian J

2015-07-01

The clinico-neuroradiological syndrome posterior cortical atrophy is the cardinal 'visual dementia' and most common atypical Alzheimer's disease phenotype, offering insights into mechanisms underlying clinical heterogeneity, pathological propagation and basic visual phenomena (e.g. visual crowding). Given the extensive attention paid to patients' (higher order) perceptual function, it is surprising that there have been no systematic analyses of basic oculomotor function in this population. Here 20 patients with posterior cortical atrophy, 17 patients with typical Alzheimer's disease and 22 healthy controls completed tests of fixation, saccade (including fixation/target gap and overlap conditions) and smooth pursuit eye movements using an infrared pupil-tracking system. Participants underwent detailed neuropsychological and neurological examinations, with a proportion also undertaking brain imaging and analysis of molecular pathology. In contrast to informal clinical evaluations of oculomotor dysfunction frequency (previous studies: 38%, current clinical examination: 33%), detailed eyetracking investigations revealed eye movement abnormalities in 80% of patients with posterior cortical atrophy (compared to 17% typical Alzheimer's disease, 5% controls). The greatest differences between posterior cortical atrophy and typical Alzheimer's disease were seen in saccadic performance. Patients with posterior cortical atrophy made significantly shorter saccades especially for distant targets. They also exhibited a significant exacerbation of the normal gap/overlap effect, consistent with 'sticky fixation'. Time to reach saccadic targets was significantly associated with parietal and occipital cortical thickness measures. On fixation stability tasks, patients with typical Alzheimer's disease showed more square wave jerks whose frequency was associated with lower cerebellar grey matter volume, while patients with posterior cortical atrophy showed large saccadic intrusions

Abnormalities of fixation, saccade and pursuit in posterior cortical atrophy

PubMed Central

Kaski, Diego; Yong, Keir X. X.; Paterson, Ross W.; Slattery, Catherine F.; Ryan, Natalie S.; Schott, Jonathan M.; Crutch, Sebastian J.

2015-01-01

The clinico-neuroradiological syndrome posterior cortical atrophy is the cardinal ‘visual dementia’ and most common atypical Alzheimer’s disease phenotype, offering insights into mechanisms underlying clinical heterogeneity, pathological propagation and basic visual phenomena (e.g. visual crowding). Given the extensive attention paid to patients’ (higher order) perceptual function, it is surprising that there have been no systematic analyses of basic oculomotor function in this population. Here 20 patients with posterior cortical atrophy, 17 patients with typical Alzheimer’s disease and 22 healthy controls completed tests of fixation, saccade (including fixation/target gap and overlap conditions) and smooth pursuit eye movements using an infrared pupil-tracking system. Participants underwent detailed neuropsychological and neurological examinations, with a proportion also undertaking brain imaging and analysis of molecular pathology. In contrast to informal clinical evaluations of oculomotor dysfunction frequency (previous studies: 38%, current clinical examination: 33%), detailed eyetracking investigations revealed eye movement abnormalities in 80% of patients with posterior cortical atrophy (compared to 17% typical Alzheimer’s disease, 5% controls). The greatest differences between posterior cortical atrophy and typical Alzheimer’s disease were seen in saccadic performance. Patients with posterior cortical atrophy made significantly shorter saccades especially for distant targets. They also exhibited a significant exacerbation of the normal gap/overlap effect, consistent with ‘sticky fixation’. Time to reach saccadic targets was significantly associated with parietal and occipital cortical thickness measures. On fixation stability tasks, patients with typical Alzheimer’s disease showed more square wave jerks whose frequency was associated with lower cerebellar grey matter volume, while patients with posterior cortical atrophy showed large

Modeling Inter-trial Variability of Saccade Trajectories: Effects of Lesions of the Oculomotor Part of the Fastigial Nucleus

PubMed Central

Eggert, Thomas; Straube, Andreas

2016-01-01

This study investigates the inter-trial variability of saccade trajectories observed in five rhesus macaques (Macaca mulatta). For each time point during a saccade, the inter-trial variance of eye position and its covariance with eye end position were evaluated. Data were modeled by a superposition of three noise components due to 1) planning noise, 2) signal-dependent motor noise, and 3) signal-dependent premotor noise entering within an internal feedback loop. Both planning noise and signal-dependent motor noise (together called accumulating noise) predict a simple S-shaped variance increase during saccades, which was not sufficient to explain the data. Adding noise within an internal feedback loop enabled the model to mimic variance/covariance structure in each monkey, and to estimate the noise amplitudes and the feedback gain. Feedback noise had little effect on end point noise, which was dominated by accumulating noise. This analysis was further extended to saccades executed during inactivation of the caudal fastigial nucleus (cFN) on one side of the cerebellum. Saccades ipsiversive to an inactivated cFN showed more end point variance than did normal saccades. During cFN inactivation, eye position during saccades was statistically more strongly coupled to eye position at saccade end. The proposed model could fit the variance/covariance structure of ipsiversive and contraversive saccades. Inactivation effects on saccade noise are explained by a decrease of the feedback gain and an increase of planning and/or signal-dependent motor noise. The decrease of the fitted feedback gain is consistent with previous studies suggesting a role for the cerebellum in an internal feedback mechanism. Increased end point variance did not result from impaired feedback but from the increase of accumulating noise. The effects of cFN inactivation on saccade noise indicate that the effects of cFN inactivation cannot be explained entirely with the cFN’s direct connections to the

The effects of ion channel blockers validate the conductance-based model of saccadic oscillations

PubMed Central

Shaikh, Aasef G.; Zee, David S.; Optican, Lance M.; Miura, Kenichiro; Ramat, Stefano; Leigh, R. John

2012-01-01

Conductance-based models of reciprocally inhibiting burst neurons suggest that intrinsic membrane properties and postinhibitory rebound (PIR) determine the amplitude and frequency of saccadic oscillations. Reduction of the low-threshold calcium currents (IT) in the model decreased the amplitude but increased the frequency of the simulated oscillations. Combined reduction of hyperpolarization-activated cation current (Ih) and IT in the model abolished the simulated oscillations. We measured the effects of a selective blocker of IT (ethosuximide) in healthy subjects on the amplitude and frequency of saccadic oscillations evoked by eye closure and of a nonselective blocker of Ih and IT (propronolol) in a patient with microsaccadic oscillation and limb tremor syndrome (mSOLT). Ethosuximide significantly reduced the amplitude but increased the frequency of the saccadic oscillations during eye closure in healthy subjects. Propranolol abolished saccadic oscillations in the mSOLT patient. These results support the hypothetical role of postinhibitory rebound, Ih, and IT, in generation of saccadic oscillations and determining their kinematic properties. PMID:21950976

Treatment of inferior oblique paresis with superior oblique silicone tendon expander.

PubMed

Greenberg, Marc F; Pollard, Zane F

2005-08-01

Patients with inferior oblique eye muscle paresis may show hypotropia and apparent superior oblique muscle overaction on the side of the presumed weak inferior oblique (IO) muscle. We report 8 such patients successfully treated using unilateral silicone superior oblique (SO) tendon expanders. Eight consecutive cases over the course of 6 years from the authors' private practice are described. None had a history of head trauma or a significant neurologic event. All patients showed IO paresis by 3-step test, with incyclotorsion and SO overacton of the hypotropic (paretic) eye. Forced ductions of the hypotropic eye were normal in all cases, and the vertical strabismus was treated with placement of a 7- mm silicone SO tendon expander in the hypotropic (paretic) eye. Mean preoperative primary position hypotropia was 6.5 prism diopters (PD); mean postoperative was 0.5 PD. Seven of 8 patients had resolution of primary position hypotropia, whereas the eighth was reduced. Mean preoperative SO overaction was 3+; all patients had postoperative resolution of SO overaction. Of 4 patients with preoperative ocular torticollis, mean preoperative head tilt was 9.3 degrees; mean postoperative tilt was 2.9 degrees. Two patients' head tilts had resolved, the other 2 showed improvement. All patients showed preoperative incylclotorsion of the hypotropic (paretic) eye; inclyclotorsion resolved in all patients after the placement of a SO tendon expander. The silicone SO tendon expander effectively restores ocular alignment in IO paresis with apparent SO overaction. Associated ocular torticollis can also be improved.

Changes to Saccade Behaviors in Parkinson’s Disease Following Dancing and Observation of Dancing

PubMed Central

Cameron, Ian G. M.; Brien, Donald C.; Links, Kira; Robichaud, Sarah; Ryan, Jennifer D.; Munoz, Douglas P.; Chow, Tiffany W.

2012-01-01

Background: The traditional view of Parkinson’s disease (PD) as a motor disorder only treated by dopaminergic medications is now shifting to include non-pharmacologic interventions. We have noticed that patients with PD obtain an immediate, short-lasting benefit to mobility by the end of a dance class, suggesting some mechanism by which dancing reduces bradykinetic symptoms. We have also found that patients with PD are unimpaired at initiating highly automatic eye movements to visual stimuli (pro-saccades) but are impaired at generating willful eye movements away from visual stimuli (anti-saccades). We hypothesized that the mechanisms by which a dance class improves movement initiation may generalize to the brain networks impacted in PD (frontal lobe and basal ganglia, BG), and thus could be assessed objectively by measuring eye movements, which rely on the same neural circuitry. Methods: Participants with PD performed pro- and anti-saccades before, and after, a dance class. “Before” and “after” saccade performance measurements were compared. These measurements were then contrasted with a control condition (observing a dance class in a video), and with older and younger adult populations, who rested for an hour between measurements. Results: We found an improvement in anti-saccade performance following the observation of dance (but not following dancing), but we found a detriment in pro-saccade performance following dancing. Conclusion: We suggest that observation of dance induced plasticity changes in frontal-BG networks that are important for executive control. Dancing, in contrast, increased voluntary movement signals that benefited mobility, but interfered with the automaticity of efficient pro-saccade execution. PMID:23483834

An electrooculogram-based binary saccade sequence classification (BSSC) technique for augmentative communication and control.

PubMed

Keegan, Johnalan; Burke, Edward; Condron, James

2009-01-01

In the field of assistive technology, the electrooculogram (EOG) can be used as a channel of communication and the basis of a man-machine interface. For many people with severe motor disabilities, simple actions such as changing the TV channel require assistance. This paper describes a method of detecting saccadic eye movements and the use of a saccade sequence classification algorithm to facilitate communication and control. Saccades are fast eye movements that occurs when a person's gaze jumps from one fixation point to another. The classification is based on pre-defined sequences of saccades, guided by a static visual template (e.g. a page or poster). The template, consisting of a table of symbols each having a clearly identifiable fixation point, is situated within view of the user. To execute a particular command, the user moves his or her gaze through a pre-defined path of eye movements. This results in a well-formed sequence of saccades which are translated into a command if a match is found in a library of predefined sequences. A coordinate transformation algorithm is applied to each candidate sequence of recorded saccades to mitigate the effect of changes in the user's position and orientation relative to the visual template. Upon recognition of a saccade sequence from the library, its associated command is executed. A preliminary experiment in which two subjects were instructed to perform a series of command sequences consisting of 8 different commands are presented in the final sections. The system is also shown to be extensible to facilitate convenient text entry via an alphabetic visual template.

Updating the Premotor Theory: The Allocation of Attention Is Not Always Accompanied by Saccade Preparation

ERIC Educational Resources Information Center

Belopolsky, Artem V.; Theeuwes, Jan

2012-01-01

There is an ongoing controversy regarding the relationship between covert attention and saccadic eye movements. While there is quite some evidence that the preparation of a saccade is obligatory preceded by a shift of covert attention, the reverse is not clear: Is allocation of attention always accompanied by saccade preparation? Recently, a…

The time course of saccadic decision making: dynamic field theory.

PubMed

Wilimzig, Claudia; Schneider, Stefan; Schöner, Gregor

2006-10-01

Making a saccadic eye movement involves two decisions, the decision to initiate the saccade and the selection of the visual target of the saccade. Here we provide a theoretical account for the time-courses of these two processes, whose instabilities are the basis of decision making. We show how the cross-over from spatial averaging for fast saccades to selection for slow saccades arises from the balance between excitatory and inhibitory processes. Initiating a saccade involves overcoming fixation, as can be observed in the countermanding paradigm, which we model accounting both for the temporal evolution of the suppression probability and its dependence on fixation activity. The interaction between the two forms of decision making is demonstrated by predicting how the cross-over from averaging to selection depends on the fixation stimulus in gap-step-overlap paradigms. We discuss how the activation dynamics of our model may be mapped onto neuronal structures including the motor map and the fixation cells in superior colliculus.

Impaired Oculomotor Behavior of Children with Developmental Dyslexia in Antisaccades and Predictive Saccades Tasks

PubMed Central

Lukasova, Katerina; Silva, Isadora P.; Macedo, Elizeu C.

2016-01-01

Analysis of eye movement patterns during tracking tasks represents a potential way to identify differences in the cognitive processing and motor mechanisms underlying reading in dyslexic children before the occurrence of school failure. The current study aimed to evaluate the pattern of eye movements in antisaccades, predictive saccades and visually guided saccades in typical readers and readers with developmental dyslexia. The study included 30 children (age M = 11; SD = 1.67), 15 diagnosed with developmental dyslexia (DG) and 15 regular readers (CG), matched by age, gender and school grade. Cognitive assessment was performed prior to the eye-tracking task during which both eyes were registered using the Tobii® 1750 eye-tracking device. The results demonstrated a lower correct antisaccades rate in dyslexic children compared to the controls (p < 0.001, DG = 25%, CC = 37%). Dyslexic children also made fewer saccades in predictive latency (p < 0.001, DG = 34%, CG = 46%, predictive latency within −300–120 ms with target as 0 point). No between-group difference was found for visually guided saccades. In this task, both groups showed shorter latency for right-side targets. The results indicated altered oculomotor behavior in dyslexic children, which has been reported in previous studies. We extend these findings by demonstrating impaired implicit learning of target's time/position patterns in dyslexic children. PMID:27445945

Active Listening Delays Attentional Disengagement and Saccadic Eye Movements.

PubMed

Lester, Benjamin D; Vecera, Shaun P

2018-06-01

Successful goal-directed visual behavior depends on efficient disengagement of attention. Attention must be withdrawn from its current focus before being redeployed to a new object or internal process. Previous research has demonstrated that occupying cognitive processes with a secondary cellular phone conversation impairs attentional functioning and driving behavior. For example, attentional processing is significantly impacted by concurrent cell phone use, resulting in decreased explicit memory for on-road information. Here, we examined the impact of a critical component of cell-phone use-active listening-on the effectiveness of attentional disengagement. In the gap task-a saccadic manipulation of attentional disengagement-we measured saccade latencies while participants performed a secondary active listening task. Saccadic latencies significantly increased under an active listening load only when attention needed to be disengaged, indicating that active listening delays a disengagement operation. Simple dual-task interference did not account for the observed results. Rather, active cognitive engagement is required for measurable disengagement slowing to be observed. These results have implications for investigations of attention, gaze behavior, and distracted driving. Secondary tasks such as active listening or cell-phone conversations can have wide-ranging impacts on cognitive functioning, potentially impairing relatively elementary operations of attentional function, including disengagement.

Motor mechanisms of vertical fusion in individuals with superior oblique paresis.

PubMed

Mudgil, Ananth V; Walker, Mark; Steffen, Heimo; Guyton, David L; Zee, David S

2002-06-01

We wanted to determine the mechanisms of motor vertical fusion in patients with superior oblique paresis and to correlate these mechanisms with surgical outcomes. Ten patients with superior oblique paresis underwent 3-axis, bilateral, scleral search coil eye movement recordings. Eye movements associated with fusion were analyzed. Six patients had decompensated congenital superior oblique paresis and 4 had acquired superior oblique paresis. All patients with acquired superior oblique paresis relied predominantly on the vertical rectus muscles for motor fusion. Patients with congenital superior oblique paresis were less uniform in their mechanisms for motor fusion: 2 patients used predominantly the oblique muscles, 2 patients used predominantly the vertical recti, and 2 patients used predominantly the superior oblique in the hyperdeviated eye and the superior rectus in the hypodeviated eye. The last 2 patients developed the largest changes in torsional eye alignment relative to changes in vertical eye alignment and were the only patients to develop symptomatic surgical overcorrections. There are 3 different mechanisms for vertical fusion in individuals with superior oblique paresis, with the predominant mechanism being the vertical recti. A subset of patients with superior oblique paresis uses predominantly the superior oblique muscle in the hyperdeviated paretic eye and the superior rectus muscle in the fellow eye for fusion. This results in intorsion of both eyes, causing a large change in torsional alignment. The consequent cyclodisparity, in addition to the existing vertical deviation, may make fusion difficult. The differing patterns of vertical fusional vergence may have implications for surgical treatment.

Saccades to a remembered location elicit spatially-specific activation in human retinotopic visual cortex

PubMed Central

Geng, Joy J.; Ruff, Christian C.; Driver, Jon

2008-01-01

The possible impact upon human visual cortex from saccades to remembered target locations was investigated using fMRI. A specific location in the upper-right or upper-left visual quadrant served as the saccadic target. After a delay of 2400 msecs, an auditory signal indicated whether to execute a saccade to that location (go trial) or to cancel the saccade and remain centrally fixated (no-go). Group fMRI analysis revealed activation specific to the remembered target location for executed saccades, in contralateral lingual gyrus. No-go trials produced similar, albeit significantly reduced effects. Individual retinotopic mapping confirmed that on go trials, quadrant-specific activations arose in those parts of ventral V1, V2, and V3 that coded the target location for the saccade, whereas on no-go trials only the corresponding parts of V2 and V3 were significantly activated. These results indicate that a spatial-motor saccadic task (i.e. making an eye-movement to a remembered location) is sufficient to activate retinotopic visual cortex spatially corresponding to the target location, and that this activation is also present (though reduced) when no saccade is executed. We discuss the implications of finding that saccades to remembered locations can affect early visual cortex, not just those structures conventionally associated with eye-movements, in relation to recent ideas about attention, spatial working memory, and the notion that recently activated representations can be ‘refreshed’ when needed. PMID:18510442

A new saccadic indicator of peripheral vestibular function based on the video head impulse test

PubMed Central

MacDougall, Hamish G.; McGarvie, Leigh A.; Rogers, Stephen J.; Manzari, Leonardo; Burgess, Ann M.; Curthoys, Ian S.; Weber, Konrad P.

2016-01-01

Objective: While compensatory saccades indicate vestibular loss in the conventional head impulse test paradigm (HIMP), in which the participant fixates an earth-fixed target, we investigated a complementary suppression head impulse paradigm (SHIMP), in which the participant is fixating a head-fixed target to elicit anticompensatory saccades as a sign of vestibular function. Methods: HIMP and SHIMP eye movement responses were measured with the horizontal video head impulse test in patients with unilateral vestibular loss, patients with bilateral vestibular loss, and in healthy controls. Results: Vestibulo-ocular reflex gains showed close correlation (R2 = 0.97) with slightly lower SHIMP than HIMP gains (mean gain difference 0.06 ± 0.05 SD, p < 0.001). However, the 2 paradigms produced complementary catch-up saccade patterns: HIMP elicited compensatory saccades in patients but rarely in controls, whereas SHIMP elicited large anticompensatory saccades in controls, but smaller or no saccades in bilateral vestibular loss. Unilateral vestibular loss produced covert saccades in HIMP, but later and smaller saccades in SHIMP toward the affected side. Cumulative HIMP and SHIMP saccade amplitude differentiated patients from controls with high sensitivity and specificity. Conclusions: While compensatory saccades indicate vestibular loss in conventional HIMP, anticompensatory saccades in SHIMP using a head-fixed target indicate vestibular function. SHIMP saccades usually appear later than HIMP saccades, therefore being more salient to the naked eye and facilitating vestibulo-ocular reflex gain measurements. The new paradigm is intuitive and easy to explain to patients, and the SHIMP results complement those from the standard video head impulse test. Classification of evidence: This case-control study provides Class III evidence that SHIMP accurately identifies patients with unilateral or bilateral vestibulopathies. PMID:27251884

Abnormal tuning of saccade-related cells in pontine reticular formation of strabismic monkeys.

PubMed

Walton, Mark M G; Mustari, Michael J

2015-08-01

Strabismus is a common disorder, characterized by a chronic misalignment of the eyes and numerous visual and oculomotor abnormalities. For example, saccades are often highly disconjugate. For humans with pattern strabismus, the horizontal and vertical disconjugacies vary with eye position. In monkeys, manipulations that disturb binocular vision during the first several weeks of life result in a chronic strabismus with characteristics that closely match those in human patients. Early onset strabismus is associated with altered binocular sensitivity of neurons in visual cortex. Here we test the hypothesis that brain stem circuits specific to saccadic eye movements are abnormal. We targeted the pontine paramedian reticular formation, a structure that directly projects to the ipsilateral abducens nucleus. In normal animals, neurons in this structure are characterized by a high-frequency burst of spikes associated with ipsiversive saccades. We recorded single-unit activity from 84 neurons from four monkeys (two normal, one exotrope, and one esotrope), while they made saccades to a visual target on a tangent screen. All 24 neurons recorded from the normal animals had preferred directions within 30° of pure horizontal. For the strabismic animals, the distribution of preferred directions was normal on one side of the brain, but highly variable on the other. In fact, 12/60 neurons recorded from the strabismic animals preferred vertical saccades. Many also had unusually weak or strong bursts. These data suggest that the loss of corresponding binocular vision during infancy impairs the development of normal tuning characteristics for saccade-related neurons in brain stem. Copyright © 2015 the American Physiological Society.

Electrical Stimulation of the Primate Lateral Habenula Suppresses Saccadic Eye Movement through a Learning Mechanism

PubMed Central

Matsumoto, Masayuki; Hikosaka, Okihide

2011-01-01

The lateral habenula (LHb) is a brain structure which represents negative motivational value. Neurons in the LHb are excited by unpleasant events such as reward omission and aversive stimuli, and transmit these signals to midbrain dopamine neurons which are involved in learning and motivation. However, it remains unclear whether these phasic changes in LHb neuronal activity actually influence animal behavior. To answer this question, we artificially activated the LHb by electrical stimulation while monkeys were performing a visually guided saccade task. In one block of trials, saccades to one fixed direction (e.g., right direction) were followed by electrical stimulation of the LHb while saccades to the other direction (e.g., left direction) were not. The direction-stimulation contingency was reversed in the next block. We found that the post-saccadic stimulation of the LHb increased the latencies of saccades in subsequent trials. Notably, the increase of the latency occurred gradually as the saccade was repeatedly followed by the stimulation, suggesting that the effect of the post-saccadic stimulation was accumulated across trials. LHb stimulation starting before saccades, on the other hand, had no effect on saccade latency. Together with previous studies showing LHb activation by reward omission and aversive stimuli, the present stimulation experiment suggests that LHb activity contributes to learning to suppress actions which lead to unpleasant events. PMID:22039537

The Eye of a Mathematical Physicist

NASA Astrophysics Data System (ADS)

Hepp, Klaus

2009-03-01

In this essay we are searching for neural correlates of `doing mathematical physics'. We introduce a toy model of a mathematical physicist, a brain connected with the outside world only by vision and saccadic eye movements and interacting with a computer screen. First, we describe the neuroanatomy of the visuo-saccadic system and Listing's law, which binds saccades and the optics of the eye. Then we explain space-time transformations in the superior colliculus, the performance of a canonical cortical circuit in the frontal eye field and finally the recurrent interaction of both areas, which leads to a coherent percept of space in spite of saccades. This sets the stage in the brain for doing mathematical physics, which is analyzed in simple examples.

Consistent chronostasis effects across saccade categories imply a subcortical efferent trigger

PubMed Central

Yarrow, Kielan; Johnson, Helen; Haggard, Patrick; Rothwell, John C

2005-01-01

Saccadic chronostasis refers to the subjective temporal lengthening of the first visual stimulus perceived after an eye movement, and is most commonly experienced as the “stopped clock” illusion. Other temporal illusions arising in the context of movement (e.g. “intentional binding”) appear to depend upon the volitional nature of the preceding motor act. Here we assess chronostasis across different saccade types, ranging from highly volitional (self-timed saccades, anti saccades) to highly reflexive (peripherally-cued saccades, express saccades). Chronostasis was similar in magnitude across all these conditions, despite wide variations in their neural bases. The illusion must therefore be triggered by a “lowest common denominator” signal common to all the conditions tested and their respective neural circuits. Specifically, it is suggested that chronostasis is triggered by a low-level signal arising in response to efferent signals generated in the superior colliculus. PMID:15200711

The effect of saccade metrics on the corollary discharge contribution to perceived eye location

PubMed Central

Bansal, Sonia; Jayet Bray, Laurence C.; Peterson, Matthew S.

2015-01-01

Corollary discharge (CD) is hypothesized to provide the movement information (direction and amplitude) required to compensate for the saccade-induced disruptions to visual input. Here, we investigated to what extent these conveyed metrics influence perceptual stability in human subjects with a target-displacement detection task. Subjects made saccades to targets located at different amplitudes (4°, 6°, or 8°) and directions (horizontal or vertical). During the saccade, the target disappeared and then reappeared at a shifted location either in the same direction or opposite to the movement vector. Subjects reported the target displacement direction, and from these reports we determined the perceptual threshold for shift detection and estimate of target location. Our results indicate that the thresholds for all amplitudes and directions generally scaled with saccade amplitude. Additionally, subjects on average produced hypometric saccades with an estimated CD gain <1. Finally, we examined the contribution of different error signals to perceptual performance, the saccade error (movement-to-movement variability in saccade amplitude) and visual error (distance between the fovea and the shifted target location). Perceptual judgment was not influenced by the fluctuations in movement amplitude, and performance was largely the same across movement directions for different magnitudes of visual error. Importantly, subjects reported the correct direction of target displacement above chance level for very small visual errors (<0.75°), even when these errors were opposite the target-shift direction. Collectively, these results suggest that the CD-based compensatory mechanisms for visual disruptions are highly accurate and comparable for saccades with different metrics. PMID:25761955

Saccade Modulation by Optical and Electrical Stimulation in the Macaque Frontal Eye Field

PubMed Central

Grimaldi, Piercesare; Schweers, Nicole

2013-01-01

Recent studies have demonstrated that strong neural modulations can be evoked with optogenetic stimulation in macaque motor cortex without observing any evoked movements (Han et al., 2009, 2011; Diester et al., 2011). It remains unclear why such perturbations do not generate movements and if conditions exist under which they may evoke movements. In this study, we examine the effects of five optogenetic constructs in the macaque frontal eye field and use electrical microstimulation to assess whether optical perturbation of the local network leads to observable motor changes during optical, electrical, and combined stimulation. We report a significant increase in the probability of evoking saccadic eye movements when low current electrical stimulation is coupled to optical stimulation compared with when electrical stimulation is used alone. Experiments combining channelrhodopsin 2 (ChR2) and electrical stimulation with simultaneous fMRI revealed no discernible fMRI activity at the electrode tip with optical stimulation but strong activity with electrical stimulation. Our findings suggest that stimulation with current ChR2 optogenetic constructs generates subthreshold activity that contributes to the initiation of movements but, in most cases, is not sufficient to evoke a motor response. PMID:24133271

Discharge properties of Purkinje cells in the oculomotor vermis during visually guided saccades in the macaque monkey.

PubMed

Ohtsuka, K; Noda, H

1995-11-01

1. We previously described discharge properties of cerebellar output cells in the fastigial nucleus during ipsilateral and contralateral saccades. Fastigial cells exhibited unique responses depending on the direction of saccades and were involved in execution of accurate targeting saccades. Purkinje cells in the oculomotor vermis (lobules VIc and VII) are thought to modulate these discharges of fastigial cells. In this study we reexamine discharge properties of Purkinje cells on the basis of this hypothesis. 2. Initially we physiologically identified the right and left sides of the oculomotor vermis. Saccade-related discharges of 79 Purkinje cells were recorded from both sides of the vermis during visually guided saccades toward the sides ipsilateral and contralateral to the recording side in two trained macaque monkeys. To clarify the correlation of Purkinje cell discharge with burst activities in the fastigial nucleus during saccadic eye movements, we analyzed our data by employing methods used in the study of fastigial neurons. 3. Among the 79 cells, 56 (71%) showed burst discharges during saccades (saccadic burst cells). Of the 56 cells, 29 exhibited a peak of burst discharges in both the contralateral and ipsilateral directions (bidirectional cells). The remaining 27 saccadic burst cells showed a peak of burst discharges during either contralateral or ipsilateral saccades (unidirectional cells). Among the 79 cells, 14 (18%) exhibited a pause of discharges during contralateral saccades (pause cells). Among the 79 cells, 9 (11%) showed burst discharge during contralateral saccades followed by tonic discharge that was correlated with eye position (burst tonic cells). 4. The timing of bursts in bidirectional cells with respect to saccade onset was dependent on the direction of saccade. During ipsilateral saccades, Purkinje cells exhibited a long lead burst that built up gradually, peaked near the onset of the saccade, and terminated sharply near midsaccade. The

The effects of ion channel blockers validate the conductance-based model of saccadic oscillations.

PubMed

Shaikh, Aasef G; Zee, David S; Optican, Lance M; Miura, Kenichiro; Ramat, Stefano; Leigh, R John

2011-09-01

Conductance-based models of reciprocally inhibiting burst neurons suggest that intrinsic membrane properties and postinhibitory rebound (PIR) determine the amplitude and frequency of saccadic oscillations. Reduction of the low-threshold calcium currents (I(T)) in the model decreased the amplitude but increased the frequency of the simulated oscillations. Combined reduction of hyperpolarization-activated cation current (I(h)) and I(T) in the model abolished the simulated oscillations. We measured the effects of a selective blocker of I(T) (ethosuximide) in healthy subjects on the amplitude and frequency of saccadic oscillations evoked by eye closure and of a nonselective blocker of I(h) and I(T) (propronolol) in a patient with microsaccadic oscillation and limb tremor syndrome (mSOLT). Ethosuximide significantly reduced the amplitude but increased the frequency of the saccadic oscillations during eye closure in healthy subjects. Propranolol abolished saccadic oscillations in the mSOLT patient. These results support the hypothetical role of postinhibitory rebound, I(h), and I(T) , in generation of saccadic oscillations and determining their kinematic properties. © 2011 New York Academy of Sciences.

Learning Peri-saccadic Remapping of Receptive Field from Experience in Lateral Intraparietal Area.

PubMed

Wang, Xiao; Wu, Yan; Zhang, Mingsha; Wu, Si

2017-01-01

Our eyes move constantly at a frequency of 3-5 times per second. These movements, called saccades, induce the sweeping of visual images on the retina, yet we perceive the world as stable. It has been suggested that the brain achieves this visual stability via predictive remapping of neuronal receptive field (RF). A recent experimental study disclosed details of this remapping process in the lateral intraparietal area (LIP), that is, about the time of the saccade, the neuronal RF expands along the saccadic trajectory temporally, covering the current RF (CRF), the future RF (FRF), and the region the eye will sweep through during the saccade. A cortical wave (CW) model was also proposed, which attributes the RF remapping as a consequence of neural activity propagating in the cortex, triggered jointly by a visual stimulus and the corollary discharge (CD) signal responsible for the saccade. In this study, we investigate how this CW model is learned naturally from visual experiences at the development of the brain. We build a two-layer network, with one layer consisting of LIP neurons and the other superior colliculus (SC) neurons. Initially, neuronal connections are random and non-selective. A saccade will cause a static visual image to sweep through the retina passively, creating the effect of the visual stimulus moving in the opposite direction of the saccade. According to the spiking-time-dependent-plasticity rule, the connection path in the opposite direction of the saccade between LIP neurons and the connection path from SC to LIP are enhanced. Over many such visual experiences, the CW model is developed, which generates the peri-saccadic RF remapping in LIP as observed in the experiment.

Cultural diversity and saccade similarities: culture does not explain saccade latency differences between Chinese and Caucasian participants.

PubMed

Knox, Paul C; Wolohan, Felicity D A

2014-01-01

A central claim of cultural neuroscience is that the culture to which an individual belongs plays a key role in shaping basic cognitive processes and behaviours, including eye movement behaviour. We previously reported a robust difference in saccade behaviour between Chinese and Caucasian participants; Chinese participants are much more likely to execute low latency express saccades, in circumstances in which these are normally discouraged. To assess the extent to which this is the product of culture we compared a group of 70 Chinese overseas students (whose primary cultural exposure was that of mainland China), a group of 45 participants whose parents were Chinese but who themselves were brought up in the UK (whose primary cultural exposure was western European) and a group of 70 Caucasian participants. Results from the Schwartz Value Survey confirmed that the UK-Chinese group were culturally similar to the Caucasian group. However, their patterns of saccade latency were identical to the mainland Chinese group, and different to the Caucasian group. We conclude that at least for the relatively simple reflexive saccade behaviour we have investigated, culture cannot explain the observed differences in behaviour.

Cultural Diversity and Saccade Similarities: Culture Does Not Explain Saccade Latency Differences between Chinese and Caucasian Participants

PubMed Central

Knox, Paul C.; Wolohan, Felicity D. A.

2014-01-01

A central claim of cultural neuroscience is that the culture to which an individual belongs plays a key role in shaping basic cognitive processes and behaviours, including eye movement behaviour. We previously reported a robust difference in saccade behaviour between Chinese and Caucasian participants; Chinese participants are much more likely to execute low latency express saccades, in circumstances in which these are normally discouraged. To assess the extent to which this is the product of culture we compared a group of 70 Chinese overseas students (whose primary cultural exposure was that of mainland China), a group of 45 participants whose parents were Chinese but who themselves were brought up in the UK (whose primary cultural exposure was western European) and a group of 70 Caucasian participants. Results from the Schwartz Value Survey confirmed that the UK-Chinese group were culturally similar to the Caucasian group. However, their patterns of saccade latency were identical to the mainland Chinese group, and different to the Caucasian group. We conclude that at least for the relatively simple reflexive saccade behaviour we have investigated, culture cannot explain the observed differences in behaviour. PMID:24709988

Saccadic abnormalities in psychotic patients. I. Neuroleptic-free psychotic patients.

PubMed

Crawford, T J; Haeger, B; Kennard, C; Reveley, M A; Henderson, L

1995-05-01

Most of the previous research reporting abnormalities of rapid re-fixation eye movements (saccades) in patients with schizophrenia has used patients receiving neuroleptic medication. In this study non-neuroleptically medicated schizophrenics were compared with other psychiatric patients using a variety of saccadic paradigms to determine the specificity of saccadic dysfunction. The patient groups consisted of schizophrenics (N = 18), bipolar affectives (N = 18), anxiety neurotics (N = 10) and normal controls (N = 31), none of whom had received neuroleptic medication for the preceding 6 months. Four behavioural paradigms, reflexive, predictive, remembered and ANTI were used to elicit saccades. The primary abnormality in the schizophrenic group was a significantly increased rate of distractibility in the ANTI (saccades made towards the target rather than in an opposite direction) and REM (saccades made prior to the imperative cue) paradigms. The major neuropsychological variable predictive of these errors was Wisconsin card sort perseverative errors. These data, in conjunction with findings from previous neurological research, would seem to provide converging evidence towards dysfunction of prefrontal cortex in schizophrenia.

[Changes and disorders in voluntary saccades during development and aging].

PubMed

Hikosaka, O

1997-05-01

We examined age-dependent changes in voluntary eye movements in normal subjects (age : 5-76) using a visually guided saccade (V-saccade) task and a memory guided saccade (M-saccade) task. Changes were more evident in M-saccades. The latencies were long in children (< 12 y.o.) and elderly people (> 50 y.o.). Both young children and elderly people tended to break fixation by making a saccade to the cue stimulus that indicated the future target position. On the other hand, both young children and elderly people tended to be slow in making M-saccade promptly after the central fixation point went off. Thus, they had difficulties both in suppressing unnecessary saccades and in initiating saccades based on memory. Interestingly, similar difficulties were observed, in exaggerated forms, in patients in basal ganglia disorders, such as Parkinson's disease, juvenile parkinsonism, dopa-responsive dystonia, and hereditary progressive dystonia with marked diurnal fluctuation. These findings were consistent with the known functions of the basal ganglia which have been revealed by physiological studies using trained monkeys. The substantia nigra pars reticulata exerts tonic inhibitory influences over the superior colliculus, thereby preventing excitatory inputs from triggering unnecessary saccades. The tonic inhibition, however, is removed by a phasic inhibition largely originating in the caudate nucleus. Thus, inhibition and disinhibition are key mechanisms of the basal ganglia. In fact, experimental manipulations of these serial inhibitory pathway in the basal ganglia led either to the difficulty in initiation of saccades, especially M-saccades, or to the difficulty in suppressing unnecessary saccades. These comparisons suggest that the functions of the basal ganglia are immature in young children while they become deteriorated in elderly people.

Patients with mild Alzheimer's disease produced shorter outgoing saccades when reading sentences.

PubMed

Fernández, Gerardo; Schumacher, Marcela; Castro, Liliana; Orozco, David; Agamennoni, Osvaldo

2015-09-30

In the present work we analyzed forward saccades of thirty five elderly subjects (Controls) and of thirty five mild Alzheimer's disease (AD) during reading regular and high-predictable sentences. While they read, their eye movements were recorded. The pattern of forward saccade amplitudes as a function of word predictability was clearly longer in Controls. Our results suggest that Controls might use stored information of words for enhancing their reading performance. Further, cloze predictability increased outgoing saccades amplitudes, as this increase stronger in high-predictable sentences. Quite the contrary, patients with mild AD evidenced reduced forward saccades even at early stages of the disease. This reduction might reveal impairments in brain areas such as those corresponding to working memory, memory retrieval, and semantic memory functions that are already present at early stages of AD. Our findings might be relevant for expanding the options for the early detection and monitoring of in the early stages of AD. Furthermore, eye movements during reading could provide a new tool for measuring a drug's impact on patient's behavior. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

Nonlinear analysis of saccade speed fluctuations during combined action and perception tasks

PubMed Central

Stan, C.; Astefanoaei, C.; Pretegiani, E.; Optican, L.; Creanga, D.; Rufa, A.; Cristescu, C.P.

2014-01-01

Background: Saccades are rapid eye movements used to gather information about a scene which requires both action and perception. These are usually studied separately, so that how perception influences action is not well understood. In a dual task, where the subject looks at a target and reports a decision, subtle changes in the saccades might be caused by action-perception interactions. Studying saccades might provide insight into how brain pathways for action and for perception interact. New method: We applied two complementary methods, multifractal detrended fluctuation analysis and Lempel-Ziv complexity index to eye peak speed recorded in two experiments, a pure action task and a combined action-perception task. Results: Multifractality strength is significantly different in the two experiments, showing smaller values for dual decision task saccades compared to simple-task saccades. The normalized Lempel-Ziv complexity index behaves similarly i.e. is significantly smaller in the decision saccade task than in the simple task. Comparison with existing methods: Compared to the usual statistical and linear approaches, these analyses emphasize the character of the dynamics involved in the fluctuations and offer a sensitive tool for quantitative evaluation of the multifractal features and of the complexity measure in the saccades peak speeds when different brain circuits are involved. Conclusion: Our results prove that the peak speed fluctuations have multifractal characteristics with lower magnitude for the multifractality strength and for the complexity index when two neural pathways are simultaneously activated, demonstrating the nonlinear interaction in the brain pathways for action and perception. PMID:24854830

Stimulation of the substantia nigra influences the specification of memory-guided saccades

PubMed Central

Mahamed, Safraaz; Garrison, Tiffany J.; Shires, Joel

2013-01-01

In the absence of sensory information, we rely on past experience or memories to guide our actions. Because previous experimental and clinical reports implicate basal ganglia nuclei in the generation of movement in the absence of sensory stimuli, we ask here whether one output nucleus of the basal ganglia, the substantia nigra pars reticulata (nigra), influences the specification of an eye movement in the absence of sensory information to guide the movement. We manipulated the level of activity of neurons in the nigra by introducing electrical stimulation to the nigra at different time intervals while monkeys made saccades to different locations in two conditions: one in which the target location remained visible and a second in which the target location appeared only briefly, requiring information stored in memory to specify the movement. Electrical manipulation of the nigra occurring during the delay period of the task, when information about the target was maintained in memory, altered the direction and the occurrence of subsequent saccades. Stimulation during other intervals of the memory task or during the delay period of the visually guided saccade task had less effect on eye movements. On stimulated trials, and only when the visual stimulus was absent, monkeys occasionally (∼20% of the time) failed to make saccades. When monkeys made saccades in the absence of a visual stimulus, stimulation of the nigra resulted in a rotation of the endpoints ipsilaterally (∼2°) and increased the reaction time of contralaterally directed saccades. When the visual stimulus was present, stimulation of the nigra resulted in no significant rotation and decreased the reaction time of contralaterally directed saccades slightly. Based on these measurements, stimulation during the delay period of the memory-guided saccade task influenced the metrics of saccades much more than did stimulation during the same period of the visually guided saccade task. Because these effects

The Influence of Attention and Target Identification on Saccadic Eye Movements Depends on Prior Target Location

PubMed Central

Hardwick, David R.; Cutmore, Timothy R. H.; Hine, Trevor J.

2014-01-01

Saccadic latency is reduced by a temporal gap between fixation point and target, by identification of a target feature, and by movement in a new direction (inhibition of saccadic return, ISR). A simple additive model was compared with a shared resources model that predicts a three-way interaction. Twenty naïve participants made horizontal saccades to targets left and right of fixation in a randomised block design. There was a significant three-way interaction among the factors on saccade latency. This was revealed in a two-way interaction between feature identification and the gap versus no gap factor which was only apparent when the saccade was in the same direction as the previous saccade. No interaction was apparent when the saccade was in the opposite direction. This result supports an attentional inhibitory effect that is present during ISR to a previous location which is only partly released by the facilitative effect of feature identification and gap. Together, anticipatory error data and saccade latency interactions suggest a source of ISR at a higher level of attention, possibly localised in the dorsolateral prefrontal cortex and involving tonic activation. PMID:24719754

Effects of diphenhydramine on human eye movements.

PubMed

Hopfenbeck, J R; Cowley, D S; Radant, A; Greenblatt, D J; Roy-Byrne, P P

1995-04-01

Peak saccadic eye movement velocity (SEV) and average smooth pursuit gain (SP) are reduced in a dose-dependent manner by diazepam and provide reliable, quantitative measures of benzodiazepine agonist effects. To evaluate the specificity of these eye movement effects for agents acting at the central GABA-benzodiazepine receptor complex and the role of sedation in benzodiazepine effects, we studied eye movement effects of diphenhydramine, a sedating drug which does not act at the GABA-benzodiazepine receptor complex. Ten healthy males, aged 19-28 years, with no history of axis I psychiatric disorders or substance abuse, received 50 mg/70 kg intravenous diphenhydramine or a similar volume of saline on separate days 1 week apart. SEV, saccade latency and accuracy, SP, self-rated sedation, and short-term memory were assessed at baseline and at 5, 15, 30, 45, 60, 90 and 120 min after drug administration. Compared with placebo, diphenhydramine produced significant SEV slowing, and increases in saccade latency and self-rated sedation. There was no significant effect of diphenhydramine on smooth pursuit gain, saccade accuracy, or short-term memory. These results suggest that, like diazepam, diphenhydramine causes sedation, SEV slowing, and an increase in saccade latency. Since the degree of diphenhydramine-induced sedation was not correlated with changes in SEV or saccade latency, slowing of saccadic eye movements is unlikely to be attributable to sedation alone. Unlike diazepam, diphenhydramine does not impair smooth pursuit gain, saccadic accuracy, or memory. Different neurotransmitter systems may influence the neural pathways involved in SEV and smooth pursuit again.

Learning Peri-saccadic Remapping of Receptive Field from Experience in Lateral Intraparietal Area

PubMed Central

Wang, Xiao; Wu, Yan; Zhang, Mingsha; Wu, Si

2017-01-01

Our eyes move constantly at a frequency of 3–5 times per second. These movements, called saccades, induce the sweeping of visual images on the retina, yet we perceive the world as stable. It has been suggested that the brain achieves this visual stability via predictive remapping of neuronal receptive field (RF). A recent experimental study disclosed details of this remapping process in the lateral intraparietal area (LIP), that is, about the time of the saccade, the neuronal RF expands along the saccadic trajectory temporally, covering the current RF (CRF), the future RF (FRF), and the region the eye will sweep through during the saccade. A cortical wave (CW) model was also proposed, which attributes the RF remapping as a consequence of neural activity propagating in the cortex, triggered jointly by a visual stimulus and the corollary discharge (CD) signal responsible for the saccade. In this study, we investigate how this CW model is learned naturally from visual experiences at the development of the brain. We build a two-layer network, with one layer consisting of LIP neurons and the other superior colliculus (SC) neurons. Initially, neuronal connections are random and non-selective. A saccade will cause a static visual image to sweep through the retina passively, creating the effect of the visual stimulus moving in the opposite direction of the saccade. According to the spiking-time-dependent-plasticity rule, the connection path in the opposite direction of the saccade between LIP neurons and the connection path from SC to LIP are enhanced. Over many such visual experiences, the CW model is developed, which generates the peri-saccadic RF remapping in LIP as observed in the experiment. PMID:29249953

Tracking with the mind's eye

NASA Technical Reports Server (NTRS)

Krauzlis, R. J.; Stone, L. S.

1999-01-01

The two components of voluntary tracking eye-movements in primates, pursuit and saccades, are generally viewed as relatively independent oculomotor subsystems that move the eyes in different ways using independent visual information. Although saccades have long been known to be guided by visual processes related to perception and cognition, only recently have psychophysical and physiological studies provided compelling evidence that pursuit is also guided by such higher-order visual processes, rather than by the raw retinal stimulus. Pursuit and saccades also do not appear to be entirely independent anatomical systems, but involve overlapping neural mechanisms that might be important for coordinating these two types of eye movement during the tracking of a selected visual object. Given that the recovery of objects from real-world images is inherently ambiguous, guiding both pursuit and saccades with perception could represent an explicit strategy for ensuring that these two motor actions are driven by a single visual interpretation.

Atypical Saccadic Scanning in Autistic Spectrum Disorder

ERIC Educational Resources Information Center

Benson, Valerie; Piper, Jenna; Fletcher-Watson, Sue

2009-01-01

Saccadic scanning was examined for typically developing (TD) adults and those with autistic spectrum disorder (ASD) during inspection of the "Repin" picture (Yarbus, A. (1967). "Eye movements and vision". New York: Plenum) under two different viewing instructions: (A) material instructions ("Estimate the material circumstances of the family"); and…

The Tell-Tale Tasks: A Review of Saccadic Research in Psychiatric Patient Populations

PubMed Central

Gooding, Diane C.; Basso, Michele A.

2008-01-01

This review focuses on saccade research with adult psychiatric patients. It begins with an introduction of the various types of saccades and the tasks used to evoke them. The functional significance of the different types of eye movements is briefly discussed. Research findings regarding the saccadic performance of different adult psychiatric patient populations are discussed in detail, with particular emphasis on findings regarding error rates, response latencies, and any specific task parameters that might affect those variables. Findings regarding the symptom, neurocognitive, and neural correlates of saccadic performance and the functional significance of patients’ saccadic deficits are also discussed. We also discuss the saccadic deficits displayed by various patient groups in terms of circuitry (e.g. cortical/basal ganglia circuits) that may be implicated in the underlying pathophysiology of several of these disorders. Future directions for research in this growing area are offered. PMID:18950927

Saccadic adaptation to a systematically varying disturbance

PubMed Central

Ohl, Sven; Rolfs, Martin

2016-01-01

Saccadic adaptation maintains the correct mapping between eye movements and their targets, yet the dynamics of saccadic gain changes in the presence of systematically varying disturbances has not been extensively studied. Here we assessed changes in the gain of saccade amplitudes induced by continuous and periodic postsaccadic visual feedback. Observers made saccades following a sequence of target steps either along the horizontal meridian (Two-way adaptation) or with unconstrained saccade directions (Global adaptation). An intrasaccadic step—following a sinusoidal variation as a function of the trial number (with 3 different frequencies tested in separate blocks)—consistently displaced the target along its vector. The oculomotor system responded to the resulting feedback error by modifying saccade amplitudes in a periodic fashion with similar frequency of variation but lagging the disturbance by a few tens of trials. This periodic response was superimposed on a drift toward stronger hypometria with similar asymptotes and decay rates across stimulus conditions. The magnitude of the periodic response decreased with increasing frequency and was smaller and more delayed for Global than Two-way adaptation. These results suggest that—in addition to the well-characterized return-to-baseline response observed in protocols using constant visual feedback—the oculomotor system attempts to minimize the feedback error by integrating its variation across trials. This process resembles a convolution with an internal response function, whose structure would be determined by coefficients of the learning model. Our protocol reveals this fast learning process in single short experimental sessions, qualifying it for the study of sensorimotor learning in health and disease. PMID:27098027

Eye movements during visual search in patients with glaucoma

PubMed Central

2012-01-01

Background Glaucoma has been shown to lead to disability in many daily tasks including visual search. This study aims to determine whether the saccadic eye movements of people with glaucoma differ from those of people with normal vision, and to investigate the association between eye movements and impaired visual search. Methods Forty patients (mean age: 67 [SD: 9] years) with a range of glaucomatous visual field (VF) defects in both eyes (mean best eye mean deviation [MD]: –5.9 (SD: 5.4) dB) and 40 age-related people with normal vision (mean age: 66 [SD: 10] years) were timed as they searched for a series of target objects in computer displayed photographs of real world scenes. Eye movements were simultaneously recorded using an eye tracker. Average number of saccades per second, average saccade amplitude and average search duration across trials were recorded. These response variables were compared with measurements of VF and contrast sensitivity. Results The average rate of saccades made by the patient group was significantly smaller than the number made by controls during the visual search task (P = 0.02; mean reduction of 5.6% (95% CI: 0.1 to 10.4%). There was no difference in average saccade amplitude between the patients and the controls (P = 0.09). Average number of saccades was weakly correlated with aspects of visual function, with patients with worse contrast sensitivity (PR logCS; Spearman’s rho: 0.42; P = 0.006) and more severe VF defects (best eye MD; Spearman’s rho: 0.34; P = 0.037) tending to make less eye movements during the task. Average detection time in the search task was associated with the average rate of saccades in the patient group (Spearman’s rho = −0.65; P < 0.001) but this was not apparent in the controls. Conclusions The average rate of saccades made during visual search by this group of patients was fewer than those made by people with normal vision of a similar average age. There was wide

Direction of an initial saccade depends on radiological expertise

NASA Astrophysics Data System (ADS)

Pietrzyk, Mariusz W.; McEntee, Mark F.; Evanoff, Michael E.; Brennan, Patrick C.; Mello-Thoms, Claudia R.

2014-03-01

Purpose: To evaluate the role of radiographic details in global impression of chest x-ray images viewed by experts in thoracic and non-thoracic domains. Materials and Methods: The study was approved by IRB. Five thoracic and five non-thoracic radiologists participated in two tachistoscopic (one low pass and one with the entire frequency spectrum, each lasting 270 ms) each containing 50 PA chest radiographs with 50% prevalence of pulmonary nodule. Eye movements were monitored in order to evaluate a pre-saccade shift of visual attention, saccade latency, decision time and the time to first fixation on a pulmonary nodule. Results: Thoracic radiologists showed significantly higher pre-saccadic shift of visual attention towards pulmonary nodules once using the full frequency spectrum (p < 0.05). An initial saccade orientation made by these radiologists on full resolution images correlated at significant level with their confidence ranking of pulmonary nodules (ρ = -0.387, p < 0.001). Conclusions: Thoracic radiologists benefited from high spatial frequency appearance during a rapid presentation of chest radiograph by allocating pre-saccade attention towards pulmonary nodules. This behavior correlated with a higher number of correct decisions, followed by higher confidence in the decisions made, and briefer reaction times.

What we remember affects how we see: spatial working memory steers saccade programming.

PubMed

Wong, Jason H; Peterson, Matthew S

2013-02-01

Relationships between visual attention, saccade programming, and visual working memory have been hypothesized for over a decade. Awh, Jonides, and Reuter-Lorenz (Journal of Experimental Psychology: Human Perception and Performance 24(3):780-90, 1998) and Awh et al. (Psychological Science 10(5):433-437, 1999) proposed that rehearsing a location in memory also leads to enhanced attentional processing at that location. In regard to eye movements, Belopolsky and Theeuwes (Attention, Perception & Psychophysics 71(3):620-631, 2009) found that holding a location in working memory affects saccade programming, albeit negatively. In three experiments, we attempted to replicate the findings of Belopolsky and Theeuwes (Attention, Perception & Psychophysics 71(3):620-631, 2009) and determine whether the spatial memory effect can occur in other saccade-cuing paradigms, including endogenous central arrow cues and exogenous irrelevant singletons. In the first experiment, our results were the opposite of those in Belopolsky and Theeuwes (Attention, Perception & Psychophysics 71(3):620-631, 2009), in that we found facilitation (shorter saccade latencies) instead of inhibition when the saccade target matched the region in spatial working memory. In Experiment 2, we sought to determine whether the spatial working memory effect would generalize to other endogenous cuing tasks, such as a central arrow that pointed to one of six possible peripheral locations. As in Experiment 1, we found that saccade programming was facilitated when the cued location coincided with the saccade target. In Experiment 3, we explored how spatial memory interacts with other types of cues, such as a peripheral color singleton target or irrelevant onset. In both cases, the eyes were more likely to go to either singleton when it coincided with the location held in spatial working memory. On the basis of these results, we conclude that spatial working memory and saccade programming are likely to share common

Predictive saccade in the absence of smooth pursuit: interception of moving targets in the archer fish.

PubMed

Ben-Simon, Avi; Ben-Shahar, Ohad; Vasserman, Genadiy; Segev, Ronen

2012-12-15

Interception of fast-moving targets is a demanding task many animals solve. To handle it successfully, mammals employ both saccadic and smooth pursuit eye movements in order to confine the target to their area centralis. But how can non-mammalian vertebrates, which lack smooth pursuit, intercept moving targets? We studied this question by exploring eye movement strategies employed by archer fish, an animal that possesses an area centralis, lacks smooth pursuit eye movements, but can intercept moving targets by shooting jets of water at them. We tracked the gaze direction of fish during interception of moving targets and found that they employ saccadic eye movements based on prediction of target position when it is hit. The fish fixates on the target's initial position for ∼0.2 s from the onset of its motion, a time period used to predict whether a shot can be made before the projection of the target exits the area centralis. If the prediction indicates otherwise, the fish performs a saccade that overshoots the center of gaze beyond the present target projection on the retina, such that after the saccade the moving target remains inside the area centralis long enough to prepare and perform a shot. These results add to the growing body of knowledge on biological target tracking and may shed light on the mechanism underlying this behavior in other animals with no neural system for the generation of smooth pursuit eye movements.

Correlation between asthenopic symptoms and different measurements of convergence and reading comprehension and saccadic fixation eye movements.

PubMed

Cohen, Yuval; Segal, Ori; Barkana, Yaniv; Lederman, Robert; Zadok, David; Pras, Eran; Morad, Yair

2010-01-01

The aim of this study was to evaluate the relationship between asthenopic symptoms, convergence amplitude, reading comprehension, and saccadic eye movements in children 8 to 10 years of age. Sixty-six children age 8 to 10 years were examined. Convergence was evaluated using (1) nonaccommodative target at near and distance, (2) a near computerized stereogram, and (3) measurement of the near point of convergence (NPC). Reading ability was examined by (1) a reading comprehension test in which children had to answer questions regarding a paragraph they read and (2) the Developmental Eye Movement Test (DEM), which evaluates saccadic speed and accuracy. Asthenopic symptoms were scored by an Asthenopic Symptoms Questionnaire. Asthenopic symptoms score was correlated with the near point of convergence (r = -0.4; P = 0.003), convergence on a near stereogram (r = 0.38; P = 0.01) and distant light (r = 0.27; P = 0.04), but not with convergence on a near nonaccommodative target (r = 0.07; P = 0.6). The DEM ratio score was correlated with the asthenopic symptoms score (r = -0.32; P = 0.01), but the reading comprehension test score was not (r = 0.12; P = 0.4). There was correlation, however, between the time for completion of the reading comprehension test and the asthenopic symptoms score (r = 0.39; P = 0.006). Asthenopic symptoms score was correlated with convergence amplitude as measured, whereas accommodation is controlled and the ratio score calculated based upon DEM results. Further study is needed to evaluate the usefulness of the integration between symptom survey and objective reading examinations as screening tool for the diagnosis of convergence insufficiency.

Updating the premotor theory: the allocation of attention is not always accompanied by saccade preparation.

PubMed

Belopolsky, Artem V; Theeuwes, Jan

2012-08-01

There is an ongoing controversy regarding the relationship between covert attention and saccadic eye movements. While there is quite some evidence that the preparation of a saccade is obligatory preceded by a shift of covert attention, the reverse is not clear: Is allocation of attention always accompanied by saccade preparation? Recently, a shifting and maintenance account was proposed suggesting that shifting and maintenance components of covert attention differ in their relation to the oculomotor system. Specifically, it was argued that a shift of covert attention is always accompanied by activation of the oculomotor program, while maintaining covert attention at a location can be accompanied either by activation or suppression of oculomotor program, depending on the probability of executing an eye movement to the attended location. In the present study we tested whether there is such an obligatory coupling between shifting of attention and saccade preparation and how quickly saccade preparation gets suppressed. The results showed that attention shifting was always accompanied by saccade preparation whenever covert attention had to be shifted during visual search, as well as in response to exogenous or endogenous cues. However, for the endogenous cues the saccade program to the attended location was suppressed very soon after the attention shift was completed. The current findings support the shifting and maintenance account and indicate that the premotor theory needs to be updated to include a shifting and maintenance component for the cases in which covert shifts of attention are made without the intention to execute a saccade. (c) 2012 APA, all rights reserved.

What and where information in the caudate tail guides saccades to visual objects

PubMed Central

Yamamoto, Shinya; Monosov, Ilya E.; Yasuda, Masaharu; Hikosaka, Okihide

2012-01-01

We understand the world by making saccadic eye movements to various objects. However, it is unclear how a saccade can be aimed at a particular object, because two kinds of visual information, what the object is and where it is, are processed separately in the dorsal and ventral visual cortical pathways. Here we provide evidence suggesting that a basal ganglia circuit through the tail of the monkey caudate nucleus (CDt) guides such object-directed saccades. First, many CDt neurons responded to visual objects depending on where and what the objects were. Second, electrical stimulation in the CDt induced saccades whose directions matched the preferred directions of neurons at the stimulation site. Third, many CDt neurons increased their activity before saccades directed to the neurons’ preferred objects and directions in a free-viewing condition. Our results suggest that CDt neurons receive both ‘what’ and ‘where’ information and guide saccades to visual objects. PMID:22875934

Saccadic adaptation to a systematically varying disturbance.

PubMed

Cassanello, Carlos R; Ohl, Sven; Rolfs, Martin

2016-08-01

Saccadic adaptation maintains the correct mapping between eye movements and their targets, yet the dynamics of saccadic gain changes in the presence of systematically varying disturbances has not been extensively studied. Here we assessed changes in the gain of saccade amplitudes induced by continuous and periodic postsaccadic visual feedback. Observers made saccades following a sequence of target steps either along the horizontal meridian (Two-way adaptation) or with unconstrained saccade directions (Global adaptation). An intrasaccadic step-following a sinusoidal variation as a function of the trial number (with 3 different frequencies tested in separate blocks)-consistently displaced the target along its vector. The oculomotor system responded to the resulting feedback error by modifying saccade amplitudes in a periodic fashion with similar frequency of variation but lagging the disturbance by a few tens of trials. This periodic response was superimposed on a drift toward stronger hypometria with similar asymptotes and decay rates across stimulus conditions. The magnitude of the periodic response decreased with increasing frequency and was smaller and more delayed for Global than Two-way adaptation. These results suggest that-in addition to the well-characterized return-to-baseline response observed in protocols using constant visual feedback-the oculomotor system attempts to minimize the feedback error by integrating its variation across trials. This process resembles a convolution with an internal response function, whose structure would be determined by coefficients of the learning model. Our protocol reveals this fast learning process in single short experimental sessions, qualifying it for the study of sensorimotor learning in health and disease. Copyright © 2016 the American Physiological Society.

A Review on Eye Movement Studies in Childhood and Adolescent Psychiatry

ERIC Educational Resources Information Center

Rommelse, Nanda N. J.; Van der Stigchel, Stefan; Sergeant, Joseph A.

2008-01-01

The neural substrates of eye movement measures are largely known. Therefore, measurement of eye movements in psychiatric disorders may provide insight into the underlying neuropathology of these disorders. Visually guided saccades, antisaccades, memory guided saccades, and smooth pursuit eye movements will be reviewed in various childhood…

Saccadic spike potentials in gamma-band EEG: characterization, detection and suppression.

PubMed

Keren, Alon S; Yuval-Greenberg, Shlomit; Deouell, Leon Y

2010-02-01

Analysis of high-frequency (gamma-band) neural activity by means of non-invasive EEG is gaining increasing interest. However, we have recently shown that a saccade-related spike potential (SP) seriously confounds the analysis of EEG induced gamma-band responses (iGBR), as the SP eludes traditional EEG artifact rejection methods. Here we provide a comprehensive profile of the SP and evaluate methods for its detection and suppression, aiming to unveil true cerebral gamma-band activity. The SP appears consistently as a sharp biphasic deflection of about 22 ms starting at the saccade onset, with a frequency band of approximately 20-90 Hz. On the average, larger saccades elicit higher SP amplitudes. The SP amplitude gradually changes from the extra-ocular channels towards posterior sites with the steepest gradients around the eyes, indicating its ocular source. Although the amplitude and the sign of the SP depend on the choice of reference channel, the potential gradients remain the same and non-zero for all references. The scalp topography is modulated almost exclusively by the direction of saccades, with steeper gradients ipsilateral to the saccade target. We discuss how the above characteristics impede attempts to remove these SPs from the EEG by common temporal filtering, choice of different references, or rejection of contaminated trials. We examine the extent to which SPs can be reliably detected without an eye tracker, assess the degree to which scalp current density derivation attenuates the effect of the SP, and propose a tailored ICA procedure for minimizing the effect of the SP. Copyright (c) 2009 Elsevier Inc. All rights reserved.

Delay activity of saccade-related neurons in the caudal dentate nucleus of the macaque cerebellum

PubMed Central

Sommer, Marc A.

2013-01-01

The caudal dentate nucleus (DN) in lateral cerebellum is connected with two visual/oculomotor areas of the cerebrum: the frontal eye field and lateral intraparietal cortex. Many neurons in frontal eye field and lateral intraparietal cortex produce “delay activity” between stimulus and response that correlates with processes such as motor planning. Our hypothesis was that caudal DN neurons would have prominent delay activity as well. From lesion studies, we predicted that this activity would be related to self-timing, i.e., the triggering of saccades based on the internal monitoring of time. We recorded from neurons in the caudal DN of monkeys (Macaca mulatta) that made delayed saccades with or without a self-timing requirement. Most (84%) of the caudal DN neurons had delay activity. These neurons conveyed at least three types of information. First, their activity was often correlated, trial by trial, with saccade initiation. Correlations were found more frequently in a task that required self-timing of saccades (53% of neurons) than in a task that did not (27% of neurons). Second, the delay activity was often tuned for saccade direction (in 65% of neurons). This tuning emerged continuously during a trial. Third, the time course of delay activity associated with self-timed saccades differed significantly from that associated with visually guided saccades (in 71% of neurons). A minority of neurons had sensory-related activity. None had presaccadic bursts, in contrast to DN neurons recorded more rostrally. We conclude that caudal DN neurons convey saccade-related delay activity that may contribute to the motor preparation of when and where to move. PMID:23365182

Differential auditory-oculomotor interactions in patients with right vs. left sided subjective tinnitus: a saccade study

PubMed Central

Lang, Alexandre; Vernet, Marine; Yang, Qing; Orssaud, Christophe; Londero, Alain; Kapoula, Zoï

2013-01-01

Subjective tinnitus (ST) is a frequent but poorly understood medical condition. Recent studies demonstrated abnormalities in several types of eye movements (smooth pursuit, optokinetic nystagmus, fixation, and vergence) in ST patients. The present study investigates horizontal and vertical saccades in patients with tinnitus lateralized predominantly to the left or to the right side. Compared to left sided ST, tinnitus perceived on the right side impaired almost all the parameters of saccades (latency, amplitude, velocity, etc.) and noticeably the upward saccades. Relative to controls, saccades from both groups were more dysmetric and were characterized by increased saccade disconjugacy (i.e., poor binocular coordination). Although the precise mechanisms linking ST and saccadic control remain unexplained, these data suggest that ST can lead to detrimental auditory, visuomotor, and perhaps vestibular interactions. PMID:23550269

Accuracy of saccades to remembered targets as a function of body orientation in space

NASA Technical Reports Server (NTRS)

Vogelstein, Joshua T.; Snyder, Lawrence H.; Angelaki, Dora E.

2003-01-01

A vertical asymmetry in memory-guided saccadic eye movements has been previously demonstrated in humans and in rhesus monkeys. In the upright orientation, saccades generally land several degrees above the target. The origin of this asymmetry has remained unknown. In this study, we investigated whether the asymmetry in memory saccades is dependent on body orientation in space. Thus animals performed memory saccades in four different body orientations: upright, left-side-down (LSD), right-side-down (RSD), and supine. Data in all three rhesus monkeys confirm previous observations regarding a significant upward vertical asymmetry. Saccade errors made from LSD and RSD postures were partitioned into components made along the axis of gravity and along the vertical body axis. Up/down asymmetry persisted only in body coordinates but not in gravity coordinates. However, this asymmetry was generally reduced in tilted positions. Therefore the upward bias seen in memory saccades is egocentric although orientation in space might play a modulatory role.

Saccadic movement deficiencies in adults with ADHD tendencies.

PubMed

Lee, Yun-Jeong; Lee, Sangil; Chang, Munseon; Kwak, Ho-Wan

2015-12-01

The goal of the present study was to explore deficits in gaze detection and emotional value judgment during a saccadic eye movement task in adults with attention deficit/hyperactivity disorder (ADHD) tendencies. Thirty-two participants, consisting of 16 ADHD tendencies and 16 controls, were recruited from a pool of 243 university students. Among the many problems in adults with ADHDs, our research focused on the deficits in the processing of nonverbal cues, such as gaze direction and the emotional value of others' faces. In Experiment 1, a cue display containing a face with emotional value and gaze direction was followed by a target display containing two faces located on the left and right side of the display. The participant's task was to make an anti-saccade opposite to the gaze direction if the cue face was not emotionally neutral. ADHD tendencies showed more overall errors than controls in making anti-saccades. Based on the hypothesis that the exposure duration of the cue display in Experiment 1 may have been too long, we presented the cue and target display simultaneously to prevent participants from preparing saccades in advance. Participants in Experiment 2 were asked to make either a pro-saccade or an anti-saccade depending on the emotional value of the central cue face. Interestingly, significant group differences were observed for errors of omission and commission. In addition, a significant three-way interaction among groups, cue emotion, and target gaze direction suggests that the emotional recognition and gaze control systems might somehow be interconnected. The result also shows that ADHDs are more easily distracted by a task-irrelevant gaze direction. Taken together, these results suggest that tasks requiring both response inhibition (anti-saccade) and gaze-emotion recognition might be useful in developing a diagnostic test for discriminating adults with ADHDs from healthy adults.

Further Tests of a Dynamic-Adjustment Account of Saccade Targeting during the Reading of Chinese

ERIC Educational Resources Information Center

Liu, Yanping; Huang, Ren; Gao, Dingguo; Reichle, Erik D.

2017-01-01

There are two accounts of how readers of unspaced writing systems (e.g., Chinese) know where to move their eyes: (a) saccades are directed toward default targets (e.g., centers of words that have been segmented in the parafovea); or (b) saccade lengths are adjusted dynamically, as a function of ongoing parafoveal processing. This article reports…

Eye Choice for Acquisition of Targets in Alternating Strabismus

PubMed Central

Economides, John R.; Adams, Daniel L.

2014-01-01

In strabismus, potentially either eye can inform the brain about the location of a target so that an accurate saccade can be made. Sixteen human subjects with alternating exotropia were tested dichoptically while viewing stimuli on a tangent screen. Each trial began with a fixation cross visible to only one eye. After the subject fixated the cross, a peripheral target visible to only one eye flashed briefly. The subject's task was to look at it. As a rule, the eye to which the target was presented was the eye that acquired the target. However, when stimuli were presented in the far nasal visual field, subjects occasionally performed a “crossover” saccade by placing the other eye on the target. This strategy avoided the need to make a large adducting saccade. In such cases, information about target location was obtained by one eye and used to program a saccade for the other eye, with a corresponding latency increase. In 10/16 subjects, targets were presented on some trials to both eyes. Binocular sensory maps were also compiled to delineate the portions of the visual scene perceived with each eye. These maps were compared with subjects' pattern of eye choice for target acquisition. There was a correspondence between suppression scotoma maps and the eye used to acquire peripheral targets. In other words, targets were fixated by the eye used to perceive them. These studies reveal how patients with alternating strabismus, despite eye misalignment, manage to localize and capture visual targets in their environment. PMID:25355212

Reading strategies in mild to moderate strabismic amblyopia: an eye movement investigation.

PubMed

Kanonidou, Evgenia; Proudlock, Frank A; Gottlob, Irene

2010-07-01

PURPOSE. To investigate oculomotor strategies in strabismic amblyopia and evaluate abnormalities during monocular and binocular reading. METHODS. Eye movements were recorded with a head-mounted infrared video eye-tracker (250 Hz, <0.01 degrees resolution) in 20 strabismic amblyopes (mean age, 44.9 +/- 10.7 years) and 20 normal control subjects (mean age, 42.8 +/- 10.9 years) while they silently read paragraphs of text. Monocular reading comparisons were made between the amblyopic eye and the nondominant eye of control subjects and the nonamblyopic eye and the dominant eye of the control subjects. Binocular reading between the amblyopic and control subjects was also compared. RESULTS. Mean reading speed, number of progressive and regressive saccades per line, saccadic amplitude (of progressive saccades), and fixation duration were estimated. Inter- and intrasubject statistical comparisons were made. Reading speed was significantly slower in amblyopes than in control subjects during monocular reading with amblyopic (13.094 characters/s vs. 22.188 characters/s; P < 0.0001) and nonamblyopic eyes (16.241 characters/s vs. 22.349 characters/s, P < 0.0001), and binocularly (15.698 characters/s vs. 23.425 characters/s, P < 0.0001). In amblyopes, reading was significantly slower with the amblyopic eye than with the nonamblyopic eye in binocular viewing (P < 0.05). These differences were associated with significantly more regressive saccades and longer fixation durations, but not with changes in saccadic amplitudes. CONCLUSIONS. In strabismic amblyopia, reading is impaired, not only during monocular viewing with the amblyopic eye, but also with the nonamblyopic eye and binocularly, even though normal visual acuity pertains to the latter two conditions. The impaired reading performance is associated with differences in both the saccadic and fixational patterns, most likely as adaptation strategies to abnormal sensory experiences such as crowding and suppression.

Predicting the Valence of a Scene from Observers’ Eye Movements

PubMed Central

R.-Tavakoli, Hamed; Atyabi, Adham; Rantanen, Antti; Laukka, Seppo J.; Nefti-Meziani, Samia; Heikkilä, Janne

2015-01-01

Multimedia analysis benefits from understanding the emotional content of a scene in a variety of tasks such as video genre classification and content-based image retrieval. Recently, there has been an increasing interest in applying human bio-signals, particularly eye movements, to recognize the emotional gist of a scene such as its valence. In order to determine the emotional category of images using eye movements, the existing methods often learn a classifier using several features that are extracted from eye movements. Although it has been shown that eye movement is potentially useful for recognition of scene valence, the contribution of each feature is not well-studied. To address the issue, we study the contribution of features extracted from eye movements in the classification of images into pleasant, neutral, and unpleasant categories. We assess ten features and their fusion. The features are histogram of saccade orientation, histogram of saccade slope, histogram of saccade length, histogram of saccade duration, histogram of saccade velocity, histogram of fixation duration, fixation histogram, top-ten salient coordinates, and saliency map. We utilize machine learning approach to analyze the performance of features by learning a support vector machine and exploiting various feature fusion schemes. The experiments reveal that ‘saliency map’, ‘fixation histogram’, ‘histogram of fixation duration’, and ‘histogram of saccade slope’ are the most contributing features. The selected features signify the influence of fixation information and angular behavior of eye movements in the recognition of the valence of images. PMID:26407322

A nonlinear generalization of the Savitzky-Golay filter and the quantitative analysis of saccades

PubMed Central

Dai, Weiwei; Selesnick, Ivan; Rizzo, John-Ross; Rucker, Janet; Hudson, Todd

2017-01-01

The Savitzky-Golay (SG) filter is widely used to smooth and differentiate time series, especially biomedical data. However, time series that exhibit abrupt departures from their typical trends, such as sharp waves or steps, which are of physiological interest, tend to be oversmoothed by the SG filter. Hence, the SG filter tends to systematically underestimate physiological parameters in certain situations. This article proposes a generalization of the SG filter to more accurately track abrupt deviations in time series, leading to more accurate parameter estimates (e.g., peak velocity of saccadic eye movements). The proposed filtering methodology models a time series as the sum of two component time series: a low-frequency time series for which the conventional SG filter is well suited, and a second time series that exhibits instantaneous deviations (e.g., sharp waves, steps, or more generally, discontinuities in a higher order derivative). The generalized SG filter is then applied to the quantitative analysis of saccadic eye movements. It is demonstrated that (a) the conventional SG filter underestimates the peak velocity of saccades, especially those of small amplitude, and (b) the generalized SG filter estimates peak saccadic velocity more accurately than the conventional filter. PMID:28813566

A nonlinear generalization of the Savitzky-Golay filter and the quantitative analysis of saccades.

PubMed

Dai, Weiwei; Selesnick, Ivan; Rizzo, John-Ross; Rucker, Janet; Hudson, Todd

2017-08-01

The Savitzky-Golay (SG) filter is widely used to smooth and differentiate time series, especially biomedical data. However, time series that exhibit abrupt departures from their typical trends, such as sharp waves or steps, which are of physiological interest, tend to be oversmoothed by the SG filter. Hence, the SG filter tends to systematically underestimate physiological parameters in certain situations. This article proposes a generalization of the SG filter to more accurately track abrupt deviations in time series, leading to more accurate parameter estimates (e.g., peak velocity of saccadic eye movements). The proposed filtering methodology models a time series as the sum of two component time series: a low-frequency time series for which the conventional SG filter is well suited, and a second time series that exhibits instantaneous deviations (e.g., sharp waves, steps, or more generally, discontinuities in a higher order derivative). The generalized SG filter is then applied to the quantitative analysis of saccadic eye movements. It is demonstrated that (a) the conventional SG filter underestimates the peak velocity of saccades, especially those of small amplitude, and (b) the generalized SG filter estimates peak saccadic velocity more accurately than the conventional filter.

Longitudinal assessment of reflexive and volitional saccades in Niemann-Pick Type C disease during treatment with miglustat.

PubMed

Abel, Larry A; Walterfang, Mark; Stainer, Matthew J; Bowman, Elizabeth A; Velakoulis, Dennis

2015-12-21

Niemann-Pick Type C disease (NPC), is an autosomal recessive neurovisceral disorder of lipid metabolism. One characteristic feature of NPC is a vertical supranuclear gaze palsy particularly affecting saccades. However, horizontal saccades are also impaired and as a consequence a parameter related to horizontal peak saccadic velocity was used as an outcome measure in the clinical trial of miglustat, the first drug approved in several jurisdictions for the treatment of NPC. As NPC-related neuropathology is widespread in the brain we examined a wider range of horizontal saccade parameters and to determine whether these showed treatment-related improvement and, if so, if this was maintained over time. Nine adult NPC patients participated in the study; 8 were treated with miglustat for periods between 33 and 61 months. Data were available for 2 patients before their treatment commenced and 1 patient was untreated. Tasks included reflexive saccades, antisaccades and self-paced saccades, with eye movements recorded by an infrared reflectance eye tracker. Parameters analysed were reflexive saccade gain and latency, asymptotic peak saccadic velocity, HSEM-α (the slope of the peak duration-amplitude regression line), antisaccade error percentage, self-paced saccade count and time between refixations on the self-paced task. Data were analysed by plotting the change from baseline as a proportion of the baseline value at each test time and, where multiple data values were available at each session, by linear mixed effects (LME) analysis. Examination of change plots suggested some modest sustained improvement in gain, no consistent changes in asymptotic peak velocity or HSEM-α, deterioration in the already poor antisaccade error rate and sustained improvement in self-paced saccade rate. LME analysis showed statistically significant improvement in gain and the interval between self-paced saccades, with differences over time between treated and untreated patients. Both

Neuronal activity in the lateral cerebellum of the cat related to visual stimuli at rest, visually guided step modification, and saccadic eye movements

PubMed Central

Marple-Horvat, D E; Criado, J M; Armstrong, D M

1998-01-01

of saccades, increasing their discharge rate. Four-fifths of these were non-reciprocally directionally selective. Saccade-related neurones were usually susceptible to other influences, i.e. their activity was not wholly explicable in terms of saccade parameters.Substantial numbers of visually responsive neurones also discharged in relation to stepping movements while other visually responsive neurones discharged in advance of saccadic eye movements. And more than half the cells tested were active in relation both to eye movements and to stepping movements. These combinations of properties qualify even individual cerebellar neurones to participate in the co-ordination of visually guided eye and limb movements. PMID:9490874

Stimulus-response incompatibility activates cortex proximate to three eye fields

NASA Technical Reports Server (NTRS)

Merriam, E. P.; Colby, C. L.; Thulborn, K. R.; Luna, B.; Olson, C. R.; Sweeney, J. A.

2001-01-01

We used functional magnetic resonance imaging (fMRI) to investigate cortical activation during the performance of three oculomotor tasks that impose increasing levels of cognitive demand. (1) In a visually guided saccade (VGS) task, subjects made saccades to flashed targets. (2) In a compatible task, subjects made leftward and rightward saccades in response to foveal presentation of the uppercase words "LEFT" or "RIGHT." (3) In a mixed task, subjects made rightward saccades in response to the lowercase word "left" and leftward saccades in response to the lowercase word "right" on incompatible trials (60%). The remaining 40% of trials required compatible responses to uppercase words. The VGS and compatible tasks, when compared to fixation, activated the three cortical eye fields: the supplementary eye field (SEF), the frontal eye field (FEF), and the parietal eye field (PEF). The mixed task, when compared to the compatible task, activated three additional cortical regions proximate to the three eye fields: (1) rostral to the SEF in medial frontal cortex; (2) rostral to the FEF in dorsolateral prefrontal cortex (DLPFC); (3) rostral and lateral to the PEF in posterior parietal cortex. These areas may contribute to the suppression of prepotent responses and in holding novel visuomotor associations in working memory. Copyright 2001 Academic Press.

Smooth pursuitlike eye movements evoked by microstimulation in macaque nucleus reticularis tegmenti pontis.

PubMed

Yamada, T; Suzuki, D A; Yee, R D

1996-11-01

1. Smooth pursuitlike eye movements were evoked with low current microstimulation delivered to rostral portions of the nucleus reticularis tegmenti pontis (rNRTP) in alert macaques. Microstimulation sites were selected by the observation of modulations in single-cell firing rates that were correlated with periodic smoothpursuit eye movements. Current intensities ranged from 10 to 120 microA and were routinely < 40 microA. Microstimulation was delivered either in the dark with no fixation, 100 ms after a fixation target was extinguished, or during maintained fixation of a stationary or moving target. Evoked eye movements also were studied under open-loop conditions with the target image stabilized on the retina. 2. Eye movements evoked in the absence of a target rapidly accelerated to a constant velocity that was maintained for the duration of the microstimulation. Evoked eye speeds ranged from 3.7 to 23 deg/s and averaged 11 deg/s. Evoked eye speed appeared to be linearly related to initial eye position with a sensitivity to initial eye position that averaged 0.23 deg.s-1.deg-1. While some horizontal and oblique smooth eye movements were elicited, microstimulation resulted in upward eye movements in 89% of the sites. 3. Evoked eye speed was found to be dependent on microstimulation pulse frequency and current intensity. Within limits, evoked eye speed increased with increases in stimulation frequency or current intensity. For stimulation frequencies < 300-400 Hz, only smooth pursuit-like eye movements were evoked. At higher stimulation frequencies, accompanying saccades consistently were elicited. 4. Feedback of retinal image motion interacted with the evoked eye movements to decrease eye speed if the visual motion was in the opposite direction as the evoked, pursuit-like eye movements. 5. The results implicate rNRTP as part of the neuronal substrate that controls smooth-pursuit eye movements. NRTP appears to be divided functionally into a rostral, pursuit

Distinct eye movement patterns enhance dynamic visual acuity.

PubMed

Palidis, Dimitrios J; Wyder-Hodge, Pearson A; Fooken, Jolande; Spering, Miriam

2017-01-01

Dynamic visual acuity (DVA) is the ability to resolve fine spatial detail in dynamic objects during head fixation, or in static objects during head or body rotation. This ability is important for many activities such as ball sports, and a close relation has been shown between DVA and sports expertise. DVA tasks involve eye movements, yet, it is unclear which aspects of eye movements contribute to successful performance. Here we examined the relation between DVA and the kinematics of smooth pursuit and saccadic eye movements in a cohort of 23 varsity baseball players. In a computerized dynamic-object DVA test, observers reported the location of the gap in a small Landolt-C ring moving at various speeds while eye movements were recorded. Smooth pursuit kinematics-eye latency, acceleration, velocity gain, position error-and the direction and amplitude of saccadic eye movements were linked to perceptual performance. Results reveal that distinct eye movement patterns-minimizing eye position error, tracking smoothly, and inhibiting reverse saccades-were related to dynamic visual acuity. The close link between eye movement quality and DVA performance has important implications for the development of perceptual training programs to improve DVA.

Greater magnocellular saccadic suppression in high versus low autistic tendency suggests a causal path to local perceptual style.

PubMed

Crewther, David P; Crewther, Daniel; Bevan, Stephanie; Goodale, Melvyn A; Crewther, Sheila G

2015-12-01

Saccadic suppression-the reduction of visual sensitivity during rapid eye movements-has previously been proposed to reflect a specific suppression of the magnocellular visual system, with the initial neural site of that suppression at or prior to afferent visual information reaching striate cortex. Dysfunction in the magnocellular visual pathway has also been associated with perceptual and physiological anomalies in individuals with autism spectrum disorder or high autistic tendency, leading us to question whether saccadic suppression is altered in the broader autism phenotype. Here we show that individuals with high autistic tendency show greater saccadic suppression of low versus high spatial frequency gratings while those with low autistic tendency do not. In addition, those with high but not low autism spectrum quotient (AQ) demonstrated pre-cortical (35-45 ms) evoked potential differences (saccade versus fixation) to a large, low contrast, pseudo-randomly flashing bar. Both AQ groups showed similar differential visual evoked potential effects in later epochs (80-160 ms) at high contrast. Thus, the magnocellular theory of saccadic suppression appears untenable as a general description for the typically developing population. Our results also suggest that the bias towards local perceptual style reported in autism may be due to selective suppression of low spatial frequency information accompanying every saccadic eye movement.

Assessment of Attentional Workload while Driving by Eye-fixation-related Potentials

NASA Astrophysics Data System (ADS)

Takeda, Yuji; Yoshitsugu, Noritoshi; Itoh, Kazuya; Kanamori, Nobuhiro

How do drivers cope with the attentional workload of in-vehicle information technology? In the present study, we propose a new psychophysiological measure for assessing drivers' attention: eye-fixation-related potential (EFRP). EFRP is a kind of event-related brain potential measurable at the eye-movement situation that reflects how closely observers examine visual information at the eye-fixated position. In the experiment, the effects of verbal working memory load and spatial working memory load during simulated driving were examined by measuring the number of saccadic eye-movements and EFRP as the indices of drivers' attention. The results showed that the spatial working memory load affected both the number of saccadic eye-movements and the amplitude of the P100 component of EFRP, whereas the verbal working memory load affected only the number of saccadic eye-movements. This implies that drivers can perform time-sharing processing between driving and the verbal working memory task, but the decline of accuracy of visual processing during driving is inescapable when the spatial working memory load is given. The present study suggests that EFRP can provide a new index of drivers' attention, other than saccadic eye-movements.

An unbiased measure of the contributions of chroma and luminance to saccadic suppression of displacement.

PubMed

Anand, Sulekha; Bridgeman, Bruce

2002-02-01

Perception of image displacement is suppressed during saccadic eye movements. We probed the source of saccadic suppression of displacement by testing whether it selectively affects chromatic- or luminance-based motion information. Human subjects viewed a stimulus in which chromatic and luminance cues provided conflicting information about displacement direction. Apparent motion occurred during either fixation or a 19.5 degree saccade. Subjects detected motion and discriminated displacement direction in each trial. They reported motion in over 90% of fixation trials and over 70% of saccade trials. During fixation, the probability of perceiving the direction carried by chromatic cues decreased as luminance contrast increased. During saccades, subjects tended to perceive the direction indicated by luminance cues when luminance contrast was high. However, when luminance contrast was low, subjects showed no preference for the chromatic- or luminance-based direction. Thus magnocellular channels are suppressed, while stimulation of parvocellular channels is below threshold, so that neither channel drives motion perception during saccades. These results confirm that magnocellular inhibition is the source of saccadic suppression.

CarPrice versus CarpRice: Word Boundary Ambiguity Influences Saccade Target Selection during the Reading of Chinese Sentences

ERIC Educational Resources Information Center

Yan, Ming; Kliegl, Reinhold

2016-01-01

As a contribution to a theoretical debate about the degree of high-level influences on saccade targeting during sentence reading, we investigated eye movements during the reading of structurally ambiguous Chinese character strings and examined whether parafoveal word segmentation could influence saccade-target selection. As expected, ambiguous…

Do alprazolam-induced changes in saccadic eye movement and psychomotor function follow the same time course?

PubMed

Kroboth, P D; Folan, M M; Bauer, K S; Tullock, W; Wright, C E; Sweeney, J A

1998-04-01

The purpose of this study was to determine whether short-term tolerance develops to GABA-agonist-induced changes in saccadic eye movements (SEMs), and whether the time course for GABA-agonist induced onset and offset of impairment is similar for SEMs and for psychomotor function. An additional goal was to determine whether there are differences in sensitivity between SEMs and psychomotor function. Six healthy volunteers participated in this balanced double-blind, three-way crossover, single-dose study of placebo and two different dosage forms of the GABA-agonist alprazolam: a rapidly absorbed oral 1.5-mg compressed tablet (CT) and a 3.0-mg sustained release (SR) tablet. Treatments were separated by a 7-day washout period. Peak concentrations did not differ between CT and SR treatments, although area under the concentration-time curve (AUC) of alprazolam was greater after administration of SR than after CT, because plateau concentrations were attained after SR. Both SEM and psychomotor tests showed time-dependent responses consistent with the development of tolerance. SEMs discriminated the differences in rate of drug input of the CT and SR formulations, with impairment evident at low concentrations during absorption. SEM impairment also persisted longer than did psychomotor impairment. Peak saccade velocity is a more sensitive indicator of pharmacologic effects mediated by the GABA-benzodiazepine receptor complex than are psychomotor responses. This is probably the result of the very high GABA dependency of SEMs, along with their limited sensitivity to motivation.

Left-Lateralized Contributions of Saccades to Cortical Activity During a One-Back Word Recognition Task.

PubMed

Chang, Yu-Cherng C; Khan, Sheraz; Taulu, Samu; Kuperberg, Gina; Brown, Emery N; Hämäläinen, Matti S; Temereanca, Simona

2018-01-01

Saccadic eye movements are an inherent component of natural reading, yet their contribution to information processing at subsequent fixation remains elusive. Here we use anatomically-constrained magnetoencephalography (MEG) to examine cortical activity following saccades as healthy human subjects engaged in a one-back word recognition task. This activity was compared with activity following external visual stimulation that mimicked saccades. A combination of procedures was employed to eliminate saccadic ocular artifacts from the MEG signal. Both saccades and saccade-like external visual stimulation produced early-latency responses beginning ~70 ms after onset in occipital cortex and spreading through the ventral and dorsal visual streams to temporal, parietal and frontal cortices. Robust differential activity following the onset of saccades vs. similar external visual stimulation emerged during 150-350 ms in a left-lateralized cortical network. This network included: (i) left lateral occipitotemporal (LOT) and nearby inferotemporal (IT) cortex; (ii) left posterior Sylvian fissure (PSF) and nearby multimodal cortex; and (iii) medial parietooccipital (PO), posterior cingulate and retrosplenial cortices. Moreover, this left-lateralized network colocalized with word repetition priming effects. Together, results suggest that central saccadic mechanisms influence a left-lateralized language network in occipitotemporal and temporal cortex above and beyond saccadic influences at preceding stages of information processing during visual word recognition.

Left-Lateralized Contributions of Saccades to Cortical Activity During a One-Back Word Recognition Task

PubMed Central

Chang, Yu-Cherng C.; Khan, Sheraz; Taulu, Samu; Kuperberg, Gina; Brown, Emery N.; Hämäläinen, Matti S.; Temereanca, Simona

2018-01-01

Saccadic eye movements are an inherent component of natural reading, yet their contribution to information processing at subsequent fixation remains elusive. Here we use anatomically-constrained magnetoencephalography (MEG) to examine cortical activity following saccades as healthy human subjects engaged in a one-back word recognition task. This activity was compared with activity following external visual stimulation that mimicked saccades. A combination of procedures was employed to eliminate saccadic ocular artifacts from the MEG signal. Both saccades and saccade-like external visual stimulation produced early-latency responses beginning ~70 ms after onset in occipital cortex and spreading through the ventral and dorsal visual streams to temporal, parietal and frontal cortices. Robust differential activity following the onset of saccades vs. similar external visual stimulation emerged during 150–350 ms in a left-lateralized cortical network. This network included: (i) left lateral occipitotemporal (LOT) and nearby inferotemporal (IT) cortex; (ii) left posterior Sylvian fissure (PSF) and nearby multimodal cortex; and (iii) medial parietooccipital (PO), posterior cingulate and retrosplenial cortices. Moreover, this left-lateralized network colocalized with word repetition priming effects. Together, results suggest that central saccadic mechanisms influence a left-lateralized language network in occipitotemporal and temporal cortex above and beyond saccadic influences at preceding stages of information processing during visual word recognition. PMID:29867372

Neurophysiology and Neuroanatomy of Reflexive and Volitional Saccades: Evidence from Studies of Humans

PubMed Central

McDowell, Jennifer E.; Dyckman, Kara A.; Austin, Benjamin; Clementz, Brett A.

2008-01-01

This review provides a summary of the contributions made by human functional neuroimaging studies to the understanding of neural correlates of saccadic control. The generation of simple visually-guided saccades (redirections of gaze to a visual stimulus or prosaccades) and more complex volitional saccades require similar basic neural circuitry with additional neural regions supporting requisite higher level processes. The saccadic system has been studied extensively in non-human primates (e.g. single unit recordings) and humans (e.g. lesions and neuroimaging). Considerable knowledge of this system’s functional neuroanatomy makes it useful for investigating models of cognitive control. The network involved in prosaccade generation (by definition exogenously-driven) includes subcortical (striatum, thalamus, superior colliculus, and cerebellar vermis) and cortical structures (primary visual, extrastriate, and parietal cortices, and frontal and supplementary eye fields). Activation in these regions is also observed during endogenously-driven voluntary saccades (e.g. antisaccades, ocular motor delayed response or memory saccades, predictive tracking tasks and anticipatory saccades, and saccade sequencing), all of which require complex cognitive processes like inhibition and working memory. These additional requirements are supported by changes in neural activity in basic saccade circuitry and by recruitment of additional neural regions (such as prefrontal and anterior cingulate cortices). Activity in visual cortex is modulated as a function of task demands and may predict the type of saccade to be generated, perhaps via top-down control mechanisms. Neuroimaging studies suggest two foci of activation within FEF - medial and lateral - which may correspond to volitional and reflexive demands, respectively. Future research on saccade control could usefully (i) delineate important anatomical subdivisions that underlie functional differences, (ii) evaluate functional

Slower saccadic reading in Parkinson's disease.

PubMed

Jehangir, Naz; Yu, Caroline Yizhu; Song, Jeehey; Shariati, Mohammad Ali; Binder, Steven; Beyer, Jill; Santini, Veronica; Poston, Kathleen; Liao, Yaping Joyce

2018-01-01

Idiopathic Parkinson's Disease (PD) is characterized by degeneration of dopaminergic and other neurons, leading to motor and non-motor deficits. Abnormal eye movements in PD, including fixations, saccades, and convergence, are well described. However, saccadic reading, which requires serial and alternating saccades and fixations, is not well studied, despite its obvious impact on the quality of life. In this study, we assessed saccadic reading using variations of the King-Devick (KD) test, a rapid single digit number naming test, as a way to assess the ability to make serial left-to-right ocular motor movements necessary for reading. We recruited 42 treated PD patients and 80 age-matched controls and compared their reading times with a variety of measures, including age, duration of disease, Unified Parkinson's Disease Rating Scale (UPDRS), the National Eye Institute 25-Item Visual Functioning Questionnaire 25 (VFQ-25), and Montreal Cognitive assessment (MoCA) test. The subjects performed 4 trials of reading 120 single digit numbers aloud as fast as possible without making errors. In each trial, they read 3 pages (KD1, KD2, and KD3), and each page contained 40 numbers per page in 8 lines with 5 numbers/line. We found that PD patients read about 20% slower than controls on all tests (KD1, 2, and 3 tests) (p < 0.02), and both groups read irregularly spaced numbers slower than regularly spaced numbers. Having lines between numbers to guide reading (KD1 tests) did not impact reading time in both PD and controls, but increased visual crowding as a result of decreased spacing between numbers (KD3 tests) was associated with significantly slower reading times in both PD and control groups. Our study revealed that saccadic reading is slower in PD, but controls and PD patients are both impacted by visuospatial planning challenges posed by increased visual crowding and irregularity of number spacing. Reading time did not correlate with UPDRS or MoCA scores in PD patients but

On Biometrics With Eye Movements.

PubMed

Zhang, Youming; Juhola, Martti

2017-09-01

Eye movements are a relatively novel data source for biometric identification. When video cameras applied to eye tracking become smaller and more efficient, this data source could offer interesting opportunities for the development of eye movement biometrics. In this paper, we study primarily biometric identification as seen as a classification task of multiple classes, and secondarily biometric verification considered as binary classification. Our research is based on the saccadic eye movement signal measurements from 109 young subjects. In order to test the data measured, we use a procedure of biometric identification according to the one-versus-one (subject) principle. In a development from our previous research, which also involved biometric verification based on saccadic eye movements, we now apply another eye movement tracker device with a higher sampling frequency of 250 Hz. The results obtained are good, with correct identification rates at 80-90% at their best.

Reading sentences of uniform word length: Evidence for the adaptation of the preferred saccade length during reading.

PubMed

Cutter, Michael G; Drieghe, Denis; Liversedge, Simon P

2017-11-01

In the current study, the effect of removing word length variability within sentences on spatial aspects of eye movements during reading was investigated. Participants read sentences that were uniform in terms of word length, with each sentence consisting entirely of three-, four-, or five-letter words, or a combination of these word lengths. Several interesting findings emerged. Adaptation of the preferred saccade length occurred for sentences with different uniform word length; participants would be more accurate at making short saccades while reading uniform sentences of three-letter words, while they would be more accurate at making long saccades while reading uniform sentences of five-letter words. Furthermore, word skipping was affected such that three- and four-letter words were more likely, and five-letter words less likely, to be directly fixated in uniform compared to non-uniform sentences. It is argued that saccadic targeting during reading is highly adaptable and flexible toward the characteristics of the text currently being read, as opposed to the idea implemented in most current models of eye movement control during reading that readers develop a preference for making saccades of a certain length across a lifetime of experience with a given language. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

Causal Inference for Spatial Constancy across Saccades

PubMed Central

Atsma, Jeroen; Maij, Femke; Koppen, Mathieu; Irwin, David E.; Medendorp, W. Pieter

2016-01-01

Our ability to interact with the environment hinges on creating a stable visual world despite the continuous changes in retinal input. To achieve visual stability, the brain must distinguish the retinal image shifts caused by eye movements and shifts due to movements of the visual scene. This process appears not to be flawless: during saccades, we often fail to detect whether visual objects remain stable or move, which is called saccadic suppression of displacement (SSD). How does the brain evaluate the memorized information of the presaccadic scene and the actual visual feedback of the postsaccadic visual scene in the computations for visual stability? Using a SSD task, we test how participants localize the presaccadic position of the fixation target, the saccade target or a peripheral non-foveated target that was displaced parallel or orthogonal during a horizontal saccade, and subsequently viewed for three different durations. Results showed different localization errors of the three targets, depending on the viewing time of the postsaccadic stimulus and its spatial separation from the presaccadic location. We modeled the data through a Bayesian causal inference mechanism, in which at the trial level an optimal mixing of two possible strategies, integration vs. separation of the presaccadic memory and the postsaccadic sensory signals, is applied. Fits of this model generally outperformed other plausible decision strategies for producing SSD. Our findings suggest that humans exploit a Bayesian inference process with two causal structures to mediate visual stability. PMID:26967730

Greater magnocellular saccadic suppression in high versus low autistic tendency suggests a causal path to local perceptual style

PubMed Central

Crewther, David P.; Crewther, Daniel; Bevan, Stephanie; Goodale, Melvyn A.; Crewther, Sheila G.

2015-01-01

Saccadic suppression—the reduction of visual sensitivity during rapid eye movements—has previously been proposed to reflect a specific suppression of the magnocellular visual system, with the initial neural site of that suppression at or prior to afferent visual information reaching striate cortex. Dysfunction in the magnocellular visual pathway has also been associated with perceptual and physiological anomalies in individuals with autism spectrum disorder or high autistic tendency, leading us to question whether saccadic suppression is altered in the broader autism phenotype. Here we show that individuals with high autistic tendency show greater saccadic suppression of low versus high spatial frequency gratings while those with low autistic tendency do not. In addition, those with high but not low autism spectrum quotient (AQ) demonstrated pre-cortical (35–45 ms) evoked potential differences (saccade versus fixation) to a large, low contrast, pseudo-randomly flashing bar. Both AQ groups showed similar differential visual evoked potential effects in later epochs (80–160 ms) at high contrast. Thus, the magnocellular theory of saccadic suppression appears untenable as a general description for the typically developing population. Our results also suggest that the bias towards local perceptual style reported in autism may be due to selective suppression of low spatial frequency information accompanying every saccadic eye movement. PMID:27019719

Internally-generated error signals in monkey frontal eye field during an inferred motion task

PubMed Central

Ferrera, Vincent P.; Barborica, Andrei

2010-01-01

An internal model for predictive saccades in frontal cortex was investigated by recording neurons in monkey frontal eye field during an inferred motion task. Monkeys were trained to make saccades to the extrapolated position of a small moving target that was rendered temporarily invisible and whose trajectory was altered. On roughly two-thirds of the trials, monkeys made multiple saccades while the target was invisible. Primary saccades were correlated with extrapolated target position. Secondary saccades significantly reduced residual errors resulting from imperfect accuracy of the first saccade. These observations suggest that the second saccade was corrective. As there was no visual feedback, corrective saccades could only be driven by an internally generated error signal. Neuronal activity in the frontal eye field was directionally tuned prior to both primary and secondary saccades. Separate subpopulations of cells encoded either saccade direction or direction error prior to the second saccade. These results suggest that FEF neurons encode the error after the first saccade, as well as the direction of the second saccade. Hence, FEF appears to contribute to detecting and correcting movement errors based on internally generated signals. PMID:20810882

Decoding Target Distance and Saccade Amplitude from Population Activity in the Macaque Lateral Intraparietal Area (LIP)

PubMed Central

Bremmer, Frank; Kaminiarz, Andre; Klingenhoefer, Steffen; Churan, Jan

2016-01-01

Primates perform saccadic eye movements in order to bring the image of an interesting target onto the fovea. Compared to stationary targets, saccades toward moving targets are computationally more demanding since the oculomotor system must use speed and direction information about the target as well as knowledge about its own processing latency to program an adequate, predictive saccade vector. In monkeys, different brain regions have been implicated in the control of voluntary saccades, among them the lateral intraparietal area (LIP). Here we asked, if activity in area LIP reflects the distance between fovea and saccade target, or the amplitude of an upcoming saccade, or both. We recorded single unit activity in area LIP of two macaque monkeys. First, we determined for each neuron its preferred saccade direction. Then, monkeys performed visually guided saccades along the preferred direction toward either stationary or moving targets in pseudo-randomized order. LIP population activity allowed to decode both, the distance between fovea and saccade target as well as the size of an upcoming saccade. Previous work has shown comparable results for saccade direction (Graf and Andersen, 2014a,b). Hence, LIP population activity allows to predict any two-dimensional saccade vector. Functional equivalents of macaque area LIP have been identified in humans. Accordingly, our results provide further support for the concept of activity from area LIP as neural basis for the control of an oculomotor brain-machine interface. PMID:27630547

Memory-guided saccade processing in visual form agnosia (patient DF).

PubMed

Rossit, Stéphanie; Szymanek, Larissa; Butler, Stephen H; Harvey, Monika

2010-01-01

According to Milner and Goodale's model (The visual brain in action, Oxford University Press, Oxford, 2006) areas in the ventral visual stream mediate visual perception and oV-line actions, whilst regions in the dorsal visual stream mediate the on-line visual control of action. Strong evidence for this model comes from a patient (DF), who suffers from visual form agnosia after bilateral damage to the ventro-lateral occipital region, sparing V1. It has been reported that she is normal in immediate reaching and grasping, yet severely impaired when asked to perform delayed actions. Here we investigated whether this dissociation would extend to saccade execution. Neurophysiological studies and TMS work in humans have shown that the posterior parietal cortex (PPC), on the right in particular (supposedly spared in DF), is involved in the control of memory-guided saccades. Surprisingly though, we found that, just as reported for reaching and grasping, DF's saccadic accuracy was much reduced in the memory compared to the stimulus-guided condition. These data support the idea of a tight coupling of eye and hand movements and further suggest that dorsal stream structures may not be sufficient to drive memory-guided saccadic performance.

The control of voluntary eye movements: new perspectives.

PubMed

Krauzlis, Richard J

2005-04-01

Primates use two types of voluntary eye movements to track objects of interest: pursuit and saccades. Traditionally, these two eye movements have been viewed as distinct systems that are driven automatically by low-level visual inputs. However, two sets of findings argue for a new perspective on the control of voluntary eye movements. First, recent experiments have shown that pursuit and saccades are not controlled by entirely different neural pathways but are controlled by similar networks of cortical and subcortical regions and, in some cases, by the same neurons. Second, pursuit and saccades are not automatic responses to retinal inputs but are regulated by a process of target selection that involves a basic form of decision making. The selection process itself is guided by a variety of complex processes, including attention, perception, memory, and expectation. Together, these findings indicate that pursuit and saccades share a similar functional architecture. These points of similarity may hold the key for understanding how neural circuits negotiate the links between the many higher order functions that can influence behavior and the singular and coordinated motor actions that follow.

Compensation of Corneal Oblique Astigmatism by Internal Optics: a Theoretical Analysis

PubMed Central

Liu, Tao; Thibos, Larry N.

2017-01-01

Purpose Oblique astigmatism is a prominent optical aberration of peripheral vision caused by oblique incidence of rays striking the refracting surfaces of the cornea and crystalline lens. We inquired whether oblique astigmatism from these two sources should be expected, theoretically, to have the same or opposite signs across the visual field at various states of accommodation. Methods Oblique astigmatism was computed across the central visual field for a rotationally-symmetric schematic-eye using optical design software. Accommodative state was varied by altering the apical radius of curvature and separation of the biconvex lens’s two aspheric surfaces in a manner consistent with published biometry. Oblique astigmatism was evaluated separately for the whole eye, the cornea, and the isolated lens over a wide range of surface curvatures and asphericity values associated with the accommodating lens. We also computed internal oblique astigmatism by subtracting corneal oblique astigmatism from whole-eye oblique astigmatism. Results A visual field map of oblique astigmatism for the cornea in the Navarro model follows the classic, textbook description of radially-oriented axes everywhere in the field. Despite large changes in surface properties during accommodation, intrinsic astigmatism of the isolated human lens for collimated light is also radially oriented and nearly independent of accommodation both in theory and in real eyes. However, the magnitude of ocular oblique astigmatism is smaller than that of the cornea alone, indicating partial compensation by the internal optics. This implies internal oblique astigmatism (which includes wavefront propagation from the posterior surface of the cornea to the anterior surface of the lens and intrinsic lens astigmatism) must have tangentially-oriented axes. This non-classical pattern of tangential axes for internal astigmatism was traced to the influence of corneal power on the angles of incidence of rays striking the

Compensation of corneal oblique astigmatism by internal optics: a theoretical analysis.

PubMed

Liu, Tao; Thibos, Larry N

2017-05-01

Oblique astigmatism is a prominent optical aberration of peripheral vision caused by oblique incidence of rays striking the refracting surfaces of the cornea and crystalline lens. We inquired whether oblique astigmatism from these two sources should be expected, theoretically, to have the same or opposite signs across the visual field at various states of accommodation. Oblique astigmatism was computed across the central visual field for a rotationally-symmetric schematic-eye using optical design software. Accommodative state was varied by altering the apical radius of curvature and separation of the biconvex lens's two aspheric surfaces in a manner consistent with published biometry. Oblique astigmatism was evaluated separately for the whole eye, the cornea, and the isolated lens over a wide range of surface curvatures and asphericity values associated with the accommodating lens. We also computed internal oblique astigmatism by subtracting corneal oblique astigmatism from whole-eye oblique astigmatism. A visual field map of oblique astigmatism for the cornea in the Navarro model follows the classic, textbook description of radially-oriented axes everywhere in the field. Despite large changes in surface properties during accommodation, intrinsic astigmatism of the isolated human lens for collimated light is also radially oriented and nearly independent of accommodation both in theory and in real eyes. However, the magnitude of ocular oblique astigmatism is smaller than that of the cornea alone, indicating partial compensation by the internal optics. This implies internal oblique astigmatism (which includes wavefront propagation from the posterior surface of the cornea to the anterior surface of the lens and intrinsic lens astigmatism) must have tangentially-oriented axes. This non-classical pattern of tangential axes for internal astigmatism was traced to the influence of corneal power on the angles of incidence of rays striking the internal lens. Partial

Effects of strabismic amblyopia and strabismus without amblyopia on visuomotor behavior: III. Temporal eye-hand coordination during reaching.

PubMed

Niechwiej-Szwedo, Ewa; Goltz, Herbert C; Chandrakumar, Manokaraananthan; Wong, Agnes M F

2014-11-11

To examine the effects of strabismic amblyopia and strabismus only, without amblyopia, on the temporal patterns of eye-hand coordination during both the planning and execution stages of visually-guided reaching. Forty-six adults (16 with strabismic amblyopia, 14 with strabismus only, and 16 visually normal) executed reach-to-touch movements toward targets presented randomly 5° or 10° to the left or right of central fixation. Viewing conditions were binocular, monocular viewing with the amblyopic eye, and monocular viewing with the fellow eye (dominant and nondominant viewing for participants without amblyopia). Temporal coordination between eye and hand movements was examined during reach planning (interval between the initiation of saccade and reaching, i.e., saccade-to-reach planning interval) and reach execution (interval between the initiation of saccade and reach peak velocity [PV], i.e., saccade-to-reach PV interval). The frequency and dynamics of secondary reach-related saccades were also examined. The temporal patterns of eye-hand coordination prior to reach initiation were comparable among participants with strabismic amblyopia, strabismus only, and visually normal adults. However, the reach acceleration phase of participants with strabismic amblyopia and those with strabismus only were longer following target fixation (saccade-to-reach PV interval) than that of visually normal participants (P < 0.05). This effect was evident under all viewing conditions. The saccade-to-reach planning interval and the saccade-to-reach PV interval were not significantly different among participants with amblyopia with different levels of acuity and stereo acuity loss. Participants with strabismic amblyopia and strabismus only initiated secondary reach-related saccades significantly more frequently than visually normal participants. The amplitude and peak velocity of these saccades were significantly greater during amblyopic eye viewing in participants with amblyopia who

Attentional cueing: fearful body postures capture attention with saccades.

PubMed

Bannerman, Rachel L; Milders, Maarten; Sahraie, Arash

2010-05-01

According to theories of attention and emotion, threat-related stimuli (e.g., negative facial expressions) capture and hold attention. Despite these theories, previous examination of attentional cueing by threat showed no enhanced capture at brief durations. One explanation for the absence of attentional capture effects may be related to the sensitivity of the manual response measure employed. Here we extended beyond facial expressions and investigated the time course of orienting attention towards fearful body postures in the exogenous cueing task. Cue duration (20, 40, 60, or 100 ms), orientation (upright or inverted), and response mode (saccadic eye movement or manual keypress) were manipulated across three experiments. In the saccade mode, both enhanced attentional capture and impaired disengagement from fearful bodies were evident and limited to rapid cue durations (20 and 40 ms), suggesting that saccadic cueing effects emerge rapidly and are short lived. In the manual mode, fearful bodies impacted only upon the disengagement component of attention at 100 ms, suggesting that manual cueing effects emerge over longer periods of time. No cueing modulation was found for inverted presentation, suggesting that valence, not low-level image confounds, was responsible for the cueing effects. Importantly, saccades could reveal threat biases at brief cue durations consistent with current theories of emotion and attention.

Variation of axial and oblique astigmatism with accommodation across the visual field

PubMed Central

Liu, Tao; Thibos, Larry N.

2017-01-01

In this study we investigated the impact of accommodation on axial and oblique astigmatism along 12 meridians of the central 30° of visual field and explored the compensation of corneal first-surface astigmatism by the remainder of the eye's optical system. Our experimental evidence revealed no systematic effect of accommodation on either axial or oblique astigmatism for two adult populations (myopic and emmetropic eyes). Although a few subjects exhibited systematic changes in axial astigmatism during accommodation, the dioptric value of these changes was much smaller than the amount of accommodation. For most subjects, axial and oblique astigmatism of the whole eye are both less than for the cornea alone, which indicates a compensatory role for internal optics at all accommodative states in both central and peripheral vision. A new method for determining the eye's optical axis based on visual field maps of oblique astigmatism revealed that, on average, the optical axis is 4.8° temporal and 0.39° superior to the foveal line-of-sight in object space, which agrees with previous results obtained by different methodologies and implies that foveal astigmatism includes a small amount of oblique astigmatism (0.06 D on average). Customized optical models of each eye revealed that oblique astigmatism of the corneal first surface is negligible along the pupillary axis for emmetropic and myopic eyes. Individual variation in the eye's optical axis is due in part to misalignment of the corneal and internal components that is consistent with tilting of the crystalline lens relative to the pupillary axis. PMID:28362902

Microsaccade production during saccade cancelation in a stop-signal task

PubMed Central

Godlove, David C.; Schall, Jeffrey D.

2014-01-01

We obtained behavioral data to evaluate two alternative hypotheses about the neural mechanisms of gaze control. The “fixation” hypothesis states that neurons in rostral superior colliculus (SC) enforce fixation of gaze. The “microsaccade” hypothesis states that neurons in rostral SC encode microsaccades rather than fixation per se. Previously reported neuronal activity in monkey SC during the saccade stop-signal task leads to specific, dissociable behavioral predictions of these two hypotheses. When subjects are required to cancel partially-prepared saccades, imbalanced activity spreads across rostral and caudal SC with a reliable temporal profile. The microsaccade hypothesis predicts that this imbalance will lead to elevated microsaccade production biased toward the target location, while the fixation hypothesis predicts reduced microsaccade production. We tested these predictions by analyzing the microsaccades produced by 4 monkeys while they voluntarily canceled partially prepared eye movements in response to explicit stop signals. Consistent with the fixation hypothesis and contradicting the microsaccade hypothesis, we found that each subject produced significantly fewer microsaccades when normal saccades were successfully canceled. The few microsaccades escaping this inhibition tended to be directed toward the target location. We additionally investigated interactions between initiating microsaccades and inhibiting normal saccades. Reaction times were longer when microsaccades immediately preceded target presentation. However, pre-target microsaccade production did not affect stop-signal reaction time or alter the probability of canceling saccades following stop signals. These findings demonstrate that imbalanced activity within SC does not necessarily produce microsaccades and add to evidence that saccade preparation and cancelation are separate processes. PMID:25448116

The Dorsal Visual System Predicts Future and Remembers Past Eye Position

PubMed Central

Morris, Adam P.; Bremmer, Frank; Krekelberg, Bart

2016-01-01

Eye movements are essential to primate vision but introduce potentially disruptive displacements of the retinal image. To maintain stable vision, the brain is thought to rely on neurons that carry both visual signals and information about the current direction of gaze in their firing rates. We have shown previously that these neurons provide an accurate representation of eye position during fixation, but whether they are updated fast enough during saccadic eye movements to support real-time vision remains controversial. Here we show that not only do these neurons carry a fast and accurate eye-position signal, but also that they support in parallel a range of time-lagged variants, including predictive and post dictive signals. We recorded extracellular activity in four areas of the macaque dorsal visual cortex during a saccade task, including the lateral and ventral intraparietal areas (LIP, VIP), and the middle temporal (MT) and medial superior temporal (MST) areas. As reported previously, neurons showed tonic eye-position-related activity during fixation. In addition, they showed a variety of transient changes in activity around the time of saccades, including relative suppression, enhancement, and pre-saccadic bursts for one saccade direction over another. We show that a hypothetical neuron that pools this rich population activity through a weighted sum can produce an output that mimics the true spatiotemporal dynamics of the eye. Further, with different pooling weights, this downstream eye position signal (EPS) could be updated long before (<100 ms) or after (<200 ms) an eye movement. The results suggest a flexible coding scheme in which downstream computations have access to past, current, and future eye positions simultaneously, providing a basis for visual stability and delay-free visually-guided behavior. PMID:26941617

Incidental threat during visuospatial working memory in adolescent anxiety: an emotional memory-guided saccade task.

PubMed

Mueller, Sven C; Shechner, Tomer; Rosen, Dana; Nelson, Eric E; Pine, Daniel S; Ernst, Monique

2015-04-01

Pediatric anxiety disorders are among the most common psychiatric mental illnesses in children and adolescents, and are associated with abnormal cognitive control in emotional, particularly threat, contexts. In a series of studies using eye movement saccade tasks, we reported anxiety-related alterations in the interplay of inhibitory control with incentives, or with emotional distractors. The present study extends these findings to working memory (WM), and queries the interaction of spatial WM with emotional stimuli in pediatric clinical anxiety. Participants were 33 children/adolescents diagnosed with an anxiety disorder, and 22 age-matched healthy comparison youths. Participants completed a novel eye movement task, an affective variant of the memory-guided saccade task. This task assessed the influence of incidental threat on spatial WM processes during high and low cognitive load. Healthy but not anxious children/adolescents showed slowed saccade latencies during incidental threat in low-load but not high-load WM conditions. No other group effects emerged on saccade latency or accuracy. The current data suggest a differential pattern of how emotion interacts with cognitive control in healthy youth relative to anxious youth. These findings extend data from inhibitory processes, reported previously, to spatial WM in pediatric anxiety. © 2015 Wiley Periodicals, Inc.

The effect of offset cues on saccade programming and covert attention.

PubMed

Smith, Daniel T; Casteau, Soazig

2018-02-01

Salient peripheral events trigger fast, "exogenous" covert orienting. The influential premotor theory of attention argues that covert orienting of attention depends upon planned but unexecuted eye-movements. One problem with this theory is that salient peripheral events, such as offsets, appear to summon attention when used to measure covert attention (e.g., the Posner cueing task) but appear not to elicit oculomotor preparation in tasks that require overt orienting (e.g., the remote distractor paradigm). Here, we examined the effects of peripheral offsets on covert attention and saccade preparation. Experiment 1 suggested that transient offsets summoned attention in a manual detection task without triggering motor preparation planning in a saccadic localisation task, although there were a high proportion of saccadic capture errors on "no-target" trials, where a cue was presented but no target appeared. In Experiment 2, "no-target" trials were removed. Here, transient offsets produced both attentional facilitation and faster saccadic responses on valid cue trials. A third experiment showed that the permanent disappearance of an object also elicited attentional facilitation and faster saccadic reaction times. These experiments demonstrate that offsets trigger both saccade programming and covert attentional orienting, consistent with the idea that exogenous, covert orienting is tightly coupled with oculomotor activation. The finding that no-go trials attenuates oculomotor priming effects offers a way to reconcile the current findings with previous claims of a dissociation between covert attention and oculomotor control in paradigms that utilise a high proportion of catch trials.

Attention modulates trans-saccadic integration.

PubMed

Stewart, Emma E M; Schütz, Alexander C

2018-01-01

With every saccade, humans must reconcile the low resolution peripheral information available before a saccade, with the high resolution foveal information acquired after the saccade. While research has shown that we are able to integrate peripheral and foveal vision in a near-optimal manner, it is still unclear which mechanisms may underpin this important perceptual process. One potential mechanism that may moderate this integration process is visual attention. Pre-saccadic attention is a well documented phenomenon, whereby visual attention shifts to the location of an upcoming saccade before the saccade is executed. While it plays an important role in other peri-saccadic processes such as predictive remapping, the role of attention in the integration process is as yet unknown. This study aimed to determine whether the presentation of an attentional distractor during a saccade impaired trans-saccadic integration, and to measure the time-course of this impairment. Results showed that presenting an attentional distractor impaired integration performance both before saccade onset, and during the saccade, in selected subjects who showed integration in the absence of a distractor. This suggests that visual attention may be a mechanism that facilitates trans-saccadic integration. Copyright © 2017 The Author(s). Published by Elsevier Ltd.. All rights reserved.

A closer look at visually guided saccades in autism and Asperger’s disorder

PubMed Central

Johnson, Beth P.; Rinehart, Nicole J.; Papadopoulos, Nicole; Tonge, Bruce; Millist, Lynette; White, Owen; Fielding, Joanne

2012-01-01

Motor impairments have been found to be a significant clinical feature associated with autism and Asperger’s disorder (AD) in addition to core symptoms of communication and social cognition deficits. Motor deficits in high-functioning autism (HFA) and AD may differentiate these disorders, particularly with respect to the role of the cerebellum in motor functioning. Current neuroimaging and behavioral evidence suggests greater disruption of the cerebellum in HFA than AD. Investigations of ocular motor functioning have previously been used in clinical populations to assess the integrity of the cerebellar networks, through examination of saccade accuracy and the integrity of saccade dynamics. Previous investigations of visually guided saccades in HFA and AD have only assessed basic saccade metrics, such as latency, amplitude, and gain, as well as peak velocity. We used a simple visually guided saccade paradigm to further characterize the profile of visually guided saccade metrics and dynamics in HFA and AD. It was found that children with HFA, but not AD, were more inaccurate across both small (5°) and large (10°) target amplitudes, and final eye position was hypometric at 10°. These findings suggest greater functional disturbance of the cerebellum in HFA than AD, and suggest fundamental difficulties with visual error monitoring in HFA. PMID:23162442

An ocular biomechanic model for dynamic simulation of different eye movements.

PubMed

Iskander, J; Hossny, M; Nahavandi, S; Del Porto, L

2018-04-11

Simulating and analysing eye movement is useful for assessing visual system contribution to discomfort with respect to body movements, especially in virtual environments where simulation sickness might occur. It can also be used in the design of eye prosthesis or humanoid robot eye. In this paper, we present two biomechanic ocular models that are easily integrated into the available musculoskeletal models. The model was previously used to simulate eye-head coordination. The models are used to simulate and analyse eye movements. The proposed models are based on physiological and kinematic properties of the human eye. They incorporate an eye-globe, orbital suspension tissues and six muscles with their connective tissues (pulleys). Pulleys were incorporated in rectus and inferior oblique muscles. The two proposed models are the passive pulleys and the active pulleys models. Dynamic simulations of different eye movements, including fixation, saccade and smooth pursuit, are performed to validate both models. The resultant force-length curves of the models were similar to the experimental data. The simulation results show that the proposed models are suitable to generate eye movement simulations with results comparable to other musculoskeletal models. The maximum kinematic root mean square error (RMSE) is 5.68° and 4.35° for the passive and active pulley models, respectively. The analysis of the muscle forces showed realistic muscle activation with increased muscle synergy in the active pulley model. Copyright © 2018 Elsevier Ltd. All rights reserved.

Algorithm for automatic analysis of electro-oculographic data.

PubMed

Pettersson, Kati; Jagadeesan, Sharman; Lukander, Kristian; Henelius, Andreas; Haeggström, Edward; Müller, Kiti

2013-10-25

Large amounts of electro-oculographic (EOG) data, recorded during electroencephalographic (EEG) measurements, go underutilized. We present an automatic, auto-calibrating algorithm that allows efficient analysis of such data sets. The auto-calibration is based on automatic threshold value estimation. Amplitude threshold values for saccades and blinks are determined based on features in the recorded signal. The performance of the developed algorithm was tested by analyzing 4854 saccades and 213 blinks recorded in two different conditions: a task where the eye movements were controlled (saccade task) and a task with free viewing (multitask). The results were compared with results from a video-oculography (VOG) device and manually scored blinks. The algorithm achieved 93% detection sensitivity for blinks with 4% false positive rate. The detection sensitivity for horizontal saccades was between 98% and 100%, and for oblique saccades between 95% and 100%. The classification sensitivity for horizontal and large oblique saccades (10 deg) was larger than 89%, and for vertical saccades larger than 82%. The duration and peak velocities of the detected horizontal saccades were similar to those in the literature. In the multitask measurement the detection sensitivity for saccades was 97% with a 6% false positive rate. The developed algorithm enables reliable analysis of EOG data recorded both during EEG and as a separate metrics.

Context cue-dependent saccadic adaptation in rhesus macaques cannot be elicited using color

PubMed Central

Smalianchuk, Ivan; Khanna, Sanjeev B.; Smith, Matthew A.; Gandhi, Neeraj J.

2015-01-01

When the head does not move, rapid movements of the eyes called saccades are used to redirect the line of sight. Saccades are defined by a series of metrical and kinematic (evolution of a movement as a function of time) relationships. For example, the amplitude of a saccade made from one visual target to another is roughly 90% of the distance between the initial fixation point (T0) and the peripheral target (T1). However, this stereotypical relationship between saccade amplitude and initial retinal error (T1-T0) may be altered, either increased or decreased, by surreptitiously displacing a visual target during an ongoing saccade. This form of motor learning (called saccadic adaptation) has been described in both humans and monkeys. Recent experiments in humans and monkeys have suggested that internal (proprioceptive) and external (target shape, color, and/or motion) cues may be used to produce context-dependent adaptation. We tested the hypothesis that an external contextual cue (target color) could be used to evoke differential gain (actual saccade/initial retinal error) states in rhesus monkeys. We did not observe differential gain states correlated with target color regardless of whether targets were displaced along the same vector as the primary saccade or perpendicular to it. Furthermore, this observation held true regardless of whether adaptation trials using various colors and intrasaccade target displacements were randomly intermixed or presented in short or long blocks of trials. These results are consistent with hypotheses that state that color cannot be used as a contextual cue and are interpreted in light of previous studies of saccadic adaptation in both humans and monkeys. PMID:25995353

Looking away: distractor influences on saccadic trajectory and endpoint in prosaccade and antisaccade tasks.

PubMed

Laidlaw, Kaitlin E W; Zhu, Mona J H; Kingstone, Alan

2016-06-01

Successful target selection often occurs concurrently with distractor inhibition. A better understanding of the former thus requires a thorough study of the competition that arises between target and distractor representations. In the present study, we explore whether the presence of a distractor influences saccade processing via interfering with visual target and/or saccade goal representations. To do this, we asked participants to make either pro- or antisaccade eye movements to a target and measured the change in their saccade trajectory and landing position (collectively referred to as deviation) in response to distractors placed near or far from the saccade goal. The use of an antisaccade paradigm may help to distinguish between stimulus- and goal-related distractor interference, as unlike with prosaccades, these two features are dissociated in space when making a goal-directed antisaccade response away from a visual target stimulus. The present results demonstrate that for both pro- and antisaccades, distractors near the saccade goal elicited the strongest competition, as indicated by greater saccade trajectory deviation and landing position error. Though distractors far from the saccade goal elicited, on average, greater deviation away in antisaccades than in prosaccades, a time-course analysis revealed a significant effect of far-from-goal distractors in prosaccades as well. Considered together, the present findings support the view that goal-related representations most strongly influence the saccade metrics tested, though stimulus-related representations may play a smaller role in determining distractor-based interference effects on saccade execution under certain circumstances. Further, the results highlight the advantage of considering temporal changes in distractor-based interference.

Application of the System Identification Technique to Goal-Directed Saccades.

DTIC Science & Technology

1985-07-01

Saccadic eye movements are among the fastest voluntary muscle movements the human body is capable of producing and are characterized by a rapid shift of gaze ...moving the target the same distance the eyeball moves. Collewijn and Van der Mark (9), in their study of the slow phase of optokinetic nystagmus , used

Saccades and Vergence Performance in a Population of Children with Vertigo and Clinically Assessed Abnormal Vergence Capabilities

PubMed Central

Bucci, Maria Pia; Kapoula, Zoï; Bui-Quoc, Emmanuel; Bouet, Aurelie; Wiener-Vacher, Sylvette

2011-01-01

Purpose Early studies reported some abnormalities in saccade and vergence eye movements in children with vertigo and vergence deficiencies. The purpose of this study was to further examine saccade and vergence performance in a population of 44 children (mean age: 12.3±1.6 years) with vertigo symptoms and with different levels of vergence abnormalities, as assessed by static orthoptic examination (near point of convergence, prism bar and cover-uncover test). Methods Three groups were identified on the basis of the orthoptic tests: group 1 (n = 13) with vergence spasms and mildly perturbed orthoptic scores, group 2 (n = 14) with moderately perturbed orthoptic scores, and group 3 (n = 17) with severely perturbed orthoptic scores. Data were compared to those recorded from 28 healthy children of similar ages. Latency, accuracy and peak velocity of saccades and vergence movements were measured in two different conditions: gap (fixation offset 200 ms prior to target onset) and simultaneous paradigms. Binocular horizontal movements were recorded by a photoelectric device. Results Group 2 of children with vergence abnormalities showed significantly longer latency than normal children in several types of eye movements recorded. For all three groups of children with vergence abnormalities, the gain was poor, particularly for vergence movement. The peak velocity values did not differ between the different groups of children examined. Interpretation Eye movement measures together with static orthoptic evaluation allowed us to better identify children with vergence abnormalities based on their slow initiation of eye movements. Overall, these findings support the hypothesis of a central deficit in the programming and triggering of saccades and vergence in these children. PMID:21858007

iTrack: instrumented mobile electrooculography (EOG) eye-tracking in older adults and Parkinson's disease.

PubMed

Stuart, Samuel; Hickey, Aodhán; Galna, Brook; Lord, Sue; Rochester, Lynn; Godfrey, Alan

2017-01-01

Detection of saccades (fast eye-movements) within raw mobile electrooculography (EOG) data involves complex algorithms which typically process data acquired during seated static tasks only. Processing of data during dynamic tasks such as walking is relatively rare and complex, particularly in older adults or people with Parkinson's disease (PD). Development of algorithms that can be easily implemented to detect saccades is required. This study aimed to develop an algorithm for the detection and measurement of saccades in EOG data during static (sitting) and dynamic (walking) tasks, in older adults and PD. Eye-tracking via mobile EOG and infra-red (IR) eye-tracker (with video) was performed with a group of older adults (n  =  10) and PD participants (n  =  10) (⩾50 years). Horizontal saccades made between targets set 5°, 10° and 15° apart were first measured while seated. Horizontal saccades were then measured while a participant walked and executed a 40° turn left and right. The EOG algorithm was evaluated by comparing the number of correct saccade detections and agreement (ICC 2,1 ) between output from visual inspection of eye-tracker videos and IR eye-tracker. The EOG algorithm detected 75-92% of saccades compared to video inspection and IR output during static testing, with fair to excellent agreement (ICC 2,1 0.49-0.93). However, during walking EOG saccade detection reduced to 42-88% compared to video inspection or IR output, with poor to excellent (ICC 2,1 0.13-0.88) agreement between methodologies. The algorithm was robust during seated testing but less so during walking, which was likely due to increased measurement and analysis error with a dynamic task. Future studies may consider a combination of EOG and IR for comprehensive measurement.

Slower saccadic reading in Parkinson’s disease

PubMed Central

Jehangir, Naz; Yu, Caroline Yizhu; Song, Jeehey; Shariati, Mohammad Ali; Binder, Steven; Beyer, Jill; Santini, Veronica; Poston, Kathleen

2018-01-01

Idiopathic Parkinson’s Disease (PD) is characterized by degeneration of dopaminergic and other neurons, leading to motor and non-motor deficits. Abnormal eye movements in PD, including fixations, saccades, and convergence, are well described. However, saccadic reading, which requires serial and alternating saccades and fixations, is not well studied, despite its obvious impact on the quality of life. In this study, we assessed saccadic reading using variations of the King-Devick (KD) test, a rapid single digit number naming test, as a way to assess the ability to make serial left-to-right ocular motor movements necessary for reading. We recruited 42 treated PD patients and 80 age-matched controls and compared their reading times with a variety of measures, including age, duration of disease, Unified Parkinson’s Disease Rating Scale (UPDRS), the National Eye Institute 25-Item Visual Functioning Questionnaire 25 (VFQ-25), and Montreal Cognitive assessment (MoCA) test. The subjects performed 4 trials of reading 120 single digit numbers aloud as fast as possible without making errors. In each trial, they read 3 pages (KD1, KD2, and KD3), and each page contained 40 numbers per page in 8 lines with 5 numbers/line. We found that PD patients read about 20% slower than controls on all tests (KD1, 2, and 3 tests) (p < 0.02), and both groups read irregularly spaced numbers slower than regularly spaced numbers. Having lines between numbers to guide reading (KD1 tests) did not impact reading time in both PD and controls, but increased visual crowding as a result of decreased spacing between numbers (KD3 tests) was associated with significantly slower reading times in both PD and control groups. Our study revealed that saccadic reading is slower in PD, but controls and PD patients are both impacted by visuospatial planning challenges posed by increased visual crowding and irregularity of number spacing. Reading time did not correlate with UPDRS or MoCA scores in PD patients

Corollary discharge contributes to perceived eye location in monkeys

PubMed Central

Cavanaugh, James; FitzGibbon, Edmond J.; Wurtz, Robert H.

2013-01-01

Despite saccades changing the image on the retina several times per second, we still perceive a stable visual world. A possible mechanism underlying this stability is that an internal retinotopic map is updated with each saccade, with the location of objects being compared before and after the saccade. Psychophysical experiments have shown that humans derive such location information from a corollary discharge (CD) accompanying saccades. Such a CD has been identified in the monkey brain in a circuit extending from superior colliculus to frontal cortex. There is a missing piece, however. Perceptual localization is established only in humans and the CD circuit only in monkeys. We therefore extended measurement of perceptual localization to the monkey by adapting the target displacement detection task developed in humans. During saccades to targets, the target disappeared and then reappeared, sometimes at a different location. The monkeys reported the displacement direction. Detections of displacement were similar in monkeys and humans, but enhanced detection of displacement from blanking the target at the end of the saccade was observed only in humans, not in monkeys. Saccade amplitude varied across trials, but the monkey's estimates of target location did not follow that variation, indicating that eye location depended on an internal CD rather than external visual information. We conclude that monkeys use a CD to determine their new eye location after each saccade, just as humans do. PMID:23986562

Corollary discharge contributes to perceived eye location in monkeys.

PubMed

Joiner, Wilsaan M; Cavanaugh, James; FitzGibbon, Edmond J; Wurtz, Robert H

2013-11-01

Despite saccades changing the image on the retina several times per second, we still perceive a stable visual world. A possible mechanism underlying this stability is that an internal retinotopic map is updated with each saccade, with the location of objects being compared before and after the saccade. Psychophysical experiments have shown that humans derive such location information from a corollary discharge (CD) accompanying saccades. Such a CD has been identified in the monkey brain in a circuit extending from superior colliculus to frontal cortex. There is a missing piece, however. Perceptual localization is established only in humans and the CD circuit only in monkeys. We therefore extended measurement of perceptual localization to the monkey by adapting the target displacement detection task developed in humans. During saccades to targets, the target disappeared and then reappeared, sometimes at a different location. The monkeys reported the displacement direction. Detections of displacement were similar in monkeys and humans, but enhanced detection of displacement from blanking the target at the end of the saccade was observed only in humans, not in monkeys. Saccade amplitude varied across trials, but the monkey's estimates of target location did not follow that variation, indicating that eye location depended on an internal CD rather than external visual information. We conclude that monkeys use a CD to determine their new eye location after each saccade, just as humans do.

The Relationship between Saccadic Choice and Reaction Times with Manipulations of Target Value

PubMed Central

Milstein, David M.; Dorris, Michael C.

2011-01-01

Choosing the option with the highest expected value (EV; reward probability × reward magnitude) maximizes the intake of reward under conditions of uncertainty. However, human economic choices indicate that our value calculation has a subjective component whereby probability and reward magnitude are not linearly weighted. Using a similar economic framework, our goal was to characterize how subjective value influences the generation of simple motor actions. Specifically, we hypothesized that attributes of saccadic eye movements could provide insight into how rhesus monkeys, a well-studied animal model in cognitive neuroscience, subjectively value potential visual targets. In the first experiment, monkeys were free to choose by directing a saccade toward one of two simultaneously displayed targets, each of which had an uncertain outcome. In this task, choices were more likely to be allocated toward the higher valued target. In the second experiment, only one of the two possible targets appeared on each trial. In this task, saccadic reaction times (SRTs) decreased toward the higher valued target. Reward magnitude had a much stronger influence on both choices and SRTs than probability, whose effect was observed only when reward magnitude was similar for both targets. Across EV blocks, a strong relationship was observed between choice preferences and SRTs. However, choices tended to maximize at skewed values whereas SRTs varied more continuously. Lastly, SRTs were unchanged when all reward magnitudes were 1×, 1.5×, and 2× their normal amount, indicating that saccade preparation was influenced by the relative value of the targets rather than the absolute value of any single-target. We conclude that value is not only an important factor for deliberative decision making in primates, but also for the selection and preparation of simple motor actions, such as saccadic eye movements. More precisely, our results indicate that, under conditions of uncertainty, saccade

The "hypnotic state" and eye movements: Less there than meets the eye?

PubMed Central

Nordhjem, Barbara; Marcusson-Clavertz, David; Holmqvist, Kenneth

2017-01-01

Responsiveness to hypnotic procedures has been related to unusual eye behaviors for centuries. Kallio and collaborators claimed recently that they had found a reliable index for "the hypnotic state" through eye-tracking methods. Whether or not hypnotic responding involves a special state of consciousness has been part of a contentious debate in the field, so the potential validity of their claim would constitute a landmark. However, their conclusion was based on 1 highly hypnotizable individual compared with 14 controls who were not measured on hypnotizability. We sought to replicate their results with a sample screened for High (n = 16) or Low (n = 13) hypnotizability. We used a factorial 2 (high vs. low hypnotizability) x 2 (hypnosis vs. resting conditions) counterbalanced order design with these eye-tracking tasks: Fixation, Saccade, Optokinetic nystagmus (OKN), Smooth pursuit, and Antisaccade (the first three tasks has been used in Kallio et al.'s experiment). Highs reported being more deeply in hypnosis than Lows but only in the hypnotic condition, as expected. There were no significant main or interaction effects for the Fixation, OKN, or Smooth pursuit tasks. For the Saccade task both Highs and Lows had smaller saccades during hypnosis, and in the Antisaccade task both groups had slower Antisaccades during hypnosis. Although a couple of results suggest that a hypnotic condition may produce reduced eye motility, the lack of significant interactions (e.g., showing only Highs expressing a particular eye behavior during hypnosis) does not support the claim that eye behaviors (at least as measured with the techniques used) are an indicator of a "hypnotic state.” Our results do not preclude the possibility that in a more spontaneous or different setting the experience of being hypnotized might relate to specific eye behaviors. PMID:28846696

Pharmacodynamics of temazepam in primary insomnia: assessment of the value of quantitative electroencephalography and saccadic eye movements in predicting improvement of sleep.

PubMed

Tuk, B; Oberyé, J J; Pieters, M S; Schoemaker, R C; Kemp, B; van Gerven, J; Danhof, M; Kamphuisen, H A; Cohen, A F; Breimer, D D; Peck, C C

1997-10-01

Quantitative electroencephalographic parameters and saccadic eye movements are frequently used as pharmacodynamic measures of benzodiazepine effect. We investigated the relationship between these measures and the hypnotic effect. The correlation between the pharmacodynamic measures and sleep quality was determined in 21 patients with primary insomnia. The pharmacokinetic-pharmacodynamic relationships were characterized after administration of 20 mg oral temazepam. The hypnotic effect was determined on the basis of polysomnographic sleep recordings and a subjective sleep evaluation questionnaire. Correlations between pharmacodynamic measures and the improvement of sleep were investigated. The pharmacokinetic-pharmacodynamic relationships for the parameters derived from electroencephalography and saccadic eye movements showed considerable interindividual variability. Administration of temazepam led to a significant improvement in the objective parameters sleep period efficiency, wake time after sleep onset, and sleep efficiency and in the subjective assessment of sleep quality. No significant correlations were observed between the pharmacokinetic-pharmacodynamic-derived parameters and the improvement in objective or subjective sleep parameters. In subjects with primary insomnia the administration of 20 mg oral temazepam results in changes in both the pharmacodynamic measures and in quality of sleep. No individual correlations between the pharmacodynamic measures and quality of sleep were observed. We concluded that the investigated pharmacodynamic measures are of value in the first assessment of clinical efficacy and for the selection of the dose(s) to be investigated in subsequent trials that aim at showing clinical efficacy. However, the conclusive quantification of clinical efficacy should be performed only on the basis of the clinical end point itself.

Sensorimotor recovery following spaceflight may be due to frequent square-wave saccadic intrusions

NASA Technical Reports Server (NTRS)

Reschke, Millard; Somers, Jeffrey T.; Leigh, R. John; Krnavek, Jody M.; Kornilova, Ludmila; Kozlovskaya, Inessa; Bloomberg, Jacob J.; Paloski, William H.

2004-01-01

Square-wave jerks (SWJs) are small, involuntary saccades that disrupt steady fixation. We report the case of an astronaut (approximately 140 d on orbit) who showed frequent SWJs, especially postflight, but who showed no impairment of vision or decrement of postflight performance. These data support the view that SWJs do not impair vision because they are paired movements, consisting of a small saccade away from the fixation position followed, within 200 ms, by a corrective saccade that brings the eye back on target. Since many returning astronauts show a decrement of dynamic visual function during postflight locomotion, it seems possible that frequent SWJs improved this astronaut's visual function by providing postsaccadic enhancement of visual fixation, which aided postflight performance. Certainly, frequent SWJs did not impair performance in this astronaut, who had no other neurological disorder.

Saccadic Eye Movements in Adults with High-Functioning Autism Spectrum Disorder

ERIC Educational Resources Information Center

Zalla, Tiziana; Seassau, Magali; Cazalis, Fabienne; Gras, Doriane; Leboyer, Marion

2018-01-01

In this study, we examined the accuracy and dynamics of visually guided saccades in 20 adults with autism spectrum disorder, as compared to 20 typically developed adults using the Step/Overlap/Gap paradigms. Performances in participants with autistic spectrum disorder were characterized by preserved Gap/Overlap effect, but reduced gain and peak…

Pursuit Eye Movements

NASA Technical Reports Server (NTRS)

Krauzlis, Rich; Stone, Leland; Null, Cynthia H. (Technical Monitor)

1998-01-01

When viewing objects, primates use a combination of saccadic and pursuit eye movements to stabilize the retinal image of the object of regard within the high-acuity region near the fovea. Although these movements involve widespread regions of the nervous system, they mix seamlessly in normal behavior. Saccades are discrete movements that quickly direct the eyes toward a visual target, thereby translating the image of the target from an eccentric retinal location to the fovea. In contrast, pursuit is a continuous movement that slowly rotates the eyes to compensate for the motion of the visual target, minimizing the blur that can compromise visual acuity. While other mammalian species can generate smooth optokinetic eye movements - which track the motion of the entire visual surround - only primates can smoothly pursue a single small element within a complex visual scene, regardless of the motion elsewhere on the retina. This ability likely reflects the greater ability of primates to segment the visual scene, to identify individual visual objects, and to select a target of interest.

Eye movements reveal sexually dimorphic deficits in children with fetal alcohol spectrum disorder

PubMed Central

Paolozza, Angelina; Munn, Rebecca; Munoz, Douglas P.; Reynolds, James N.

2015-01-01

Background: We examined the accuracy and characteristics of saccadic eye movements in children with fetal alcohol spectrum disorder (FASD) compared with typically developing control children. Previous studies have found that children with FASD produce saccades that are quantifiably different from controls. Additionally, animal studies have found sex-based differences for behavioral effects after prenatal alcohol exposure. Therefore, we hypothesized that eye movement measures will show sexually dimorphic results. Methods: Children (aged 5–18 years) with FASD (n = 71) and typically developing controls (n = 113) performed a visually-guided saccade task. Saccade metrics and behavior were analyzed for sex and group differences. Results: Female control participants had greater amplitude saccades than control males or females with FASD. Accuracy was significantly poorer in the FASD group, especially in males, which introduced significantly greater variability in the data. Therefore, we conducted additional analyses including only those trials in which the first saccade successfully reached the target within a ± 1° window. In this restricted amplitude dataset, the females with FASD made saccades with significantly lower velocity and longer duration, whereas the males with FASD did not differ from the control group. Additionally, the mean and peak deceleration were selectively decreased in the females with FASD. Conclusions: These data support the hypothesis that children with FASD exhibit specific deficits in eye movement control and sensory-motor integration associated with cerebellar and/or brain stem circuits. Moreover, prenatal alcohol exposure may have a sexually dimorphic impact on eye movement metrics, with males and females exhibiting differential patterns of deficit. PMID:25814922

Validation of mobile eye-tracking as novel and efficient means for differentiating progressive supranuclear palsy from Parkinson's disease

PubMed Central

Marx, Svenja; Respondek, Gesine; Stamelou, Maria; Dowiasch, Stefan; Stoll, Josef; Bremmer, Frank; Oertel, Wolfgang H.; Höglinger, Günter U.; Einhäuser, Wolfgang

2012-01-01

Background: The decreased ability to carry out vertical saccades is a key symptom of Progressive Supranuclear Palsy (PSP). Objective measurement devices can help to reliably detect subtle eye movement disturbances to improve sensitivity and specificity of the clinical diagnosis. The present study aims at transferring findings from restricted stationary video-oculography (VOG) to a wearable head-mounted device, which can be readily applied in clinical practice. Methods: We investigated the eye movements in 10 possible or probable PSP patients, 11 Parkinson's disease (PD) patients, and 10 age-matched healthy controls (HCs) using a mobile, gaze-driven video camera setup (EyeSeeCam). Ocular movements were analyzed during a standardized fixation protocol and in an unrestricted real-life scenario while walking along a corridor. Results: The EyeSeeCam detected prominent impairment of both saccade velocity and amplitude in PSP patients, differentiating them from PD and HCs. Differences were particularly evident for saccades in the vertical plane, and stronger for saccades than for other eye movements. Differences were more pronounced during the standardized protocol than in the real-life scenario. Conclusions: Combined analysis of saccade velocity and saccade amplitude during the fixation protocol with the EyeSeeCam provides a simple, rapid (<20 s), and reliable tool to differentiate clinically established PSP patients from PD and HCs. As such, our findings prepare the ground for using wearable eye-tracking in patients with uncertain diagnoses. PMID:23248593

Modulation of Saccade Vigor during Value-Based Decision Making.

PubMed

Reppert, Thomas R; Lempert, Karolina M; Glimcher, Paul W; Shadmehr, Reza

2015-11-18

During value-based decision-making, individuals consider the various options and select the one that provides the maximum subjective value. Although the brain integrates abstract information to compute and compare these values, the only behavioral outcome is often the decision itself. However, if the options are visual stimuli, during deliberation the brain moves the eyes from one stimulus to the other. Previous work suggests that saccade vigor, i.e., peak velocity as a function of amplitude, is greater if reward is associated with the visual stimulus. This raises the possibility that vigor during the free viewing of options may be influenced by the valuation of each option. Here, humans chose between a small, immediate monetary reward and a larger but delayed reward. As the deliberation began, vigor was similar for the saccades made to the two options but diverged 0.5 s before decision time, becoming greater for the preferred option. This difference in vigor increased as a function of the difference in the subjective values that the participant assigned to the delayed and immediate options. After the decision was made, participants continued to gaze at the options, but with reduced vigor, making it possible to infer timing of the decision from the sudden drop in vigor. Therefore, the subjective value that the brain assigned to a stimulus during decision-making affected the motor system via the vigor with which the eyes moved toward that stimulus. We find that, as individuals deliberate between two rewarding options and arrive at a decision, the vigor with which they make saccades to each option reflects a real-time evaluation of that option. With deliberation, saccade vigor diverges between the two options, becoming greater for the option that the individual will eventually choose. The results suggest a shared element between the network that assigns value to a stimulus during the process of decision-making and the network that controls vigor of movements toward

Modulation of Saccade Vigor during Value-Based Decision Making

PubMed Central

Lempert, Karolina M.; Glimcher, Paul W.; Shadmehr, Reza

2015-01-01

During value-based decision-making, individuals consider the various options and select the one that provides the maximum subjective value. Although the brain integrates abstract information to compute and compare these values, the only behavioral outcome is often the decision itself. However, if the options are visual stimuli, during deliberation the brain moves the eyes from one stimulus to the other. Previous work suggests that saccade vigor, i.e., peak velocity as a function of amplitude, is greater if reward is associated with the visual stimulus. This raises the possibility that vigor during the free viewing of options may be influenced by the valuation of each option. Here, humans chose between a small, immediate monetary reward and a larger but delayed reward. As the deliberation began, vigor was similar for the saccades made to the two options but diverged 0.5 s before decision time, becoming greater for the preferred option. This difference in vigor increased as a function of the difference in the subjective values that the participant assigned to the delayed and immediate options. After the decision was made, participants continued to gaze at the options, but with reduced vigor, making it possible to infer timing of the decision from the sudden drop in vigor. Therefore, the subjective value that the brain assigned to a stimulus during decision-making affected the motor system via the vigor with which the eyes moved toward that stimulus. SIGNIFICANCE STATEMENT We find that, as individuals deliberate between two rewarding options and arrive at a decision, the vigor with which they make saccades to each option reflects a real-time evaluation of that option. With deliberation, saccade vigor diverges between the two options, becoming greater for the option that the individual will eventually choose. The results suggest a shared element between the network that assigns value to a stimulus during the process of decision-making and the network that controls

Is There a Vertical Component to Saccade Targeting in Chinese Reading?

ERIC Educational Resources Information Center

Zang, Chuanli; Meng, Hongxia; Liang, Feifei; Bai, Xuejun; Yan, Guoli

2013-01-01

In this study, we examined whether Chinese character structure influenced readers' saccadic targeting in Chinese reading. Readers' eye movements were recorded when they read single sentences containing one-character or two-character target words. Both the one-character words and the two constituent characters of two-character words either had a…

Cause of kinematic differences during centrifugal and centripetal saccades.

PubMed

Koene, Ansgar R; Erkelens, Casper J

2002-06-01

Measurements of eye movements have shown that centrifugal movements (i.e. away from the primary position) have a lower maximum velocity and a longer duration than centripetal movements (i.e. toward the primary position) of the same size. In 1988 Pelisson proposed that these kinematic differences might be caused by differences in the neural command signals, oculomotor mechanics or a combination of the two. By using the result of muscle force measurements that were made in recent years (Orbit 1.8 Gaze mechanics simulation, Eidactics, San Francisco, 1999) we simulated the muscle forces during centrifugal and centripetal saccades. Based on these simulations we show that the cause of the kinematic differences between the centrifugal and centripetal saccades is the non-linear force-velocity relationship (i.e. muscle viscosity) of the muscles.

Lateralization of posterior alpha EEG reflects the distribution of spatial attention during saccadic reading.

PubMed

Kornrumpf, Benthe; Dimigen, Olaf; Sommer, Werner

2017-06-01

Visuospatial attention is an important mechanism in reading that governs the uptake of information from foveal and parafoveal regions of the visual field. However, the spatiotemporal dynamics of how attention is allocated during eye fixations are not completely understood. The current study explored the use of EEG alpha-band oscillations to investigate the spatial distribution of attention during reading. We reanalyzed two data sets, focusing on the lateralization of alpha activity at posterior scalp sites. In each experiment, participants read short lists of German nouns in two paradigms: either by freely moving their eyes (saccadic reading) or by fixating the screen center while the text moved passively from right to left at the same average speed (RSVP paradigm). In both paradigms, upcoming words were either visible or masked, and foveal processing load was manipulated by varying the words' lexical frequencies. Posterior alpha lateralization revealed a sustained rightward bias of attention during saccadic reading, but not in the RSVP paradigm. Interestingly, alpha lateralization was not influenced by word frequency (foveal load) or preview during the preceding fixation. Hence, alpha did not reflect transient attention shifts within a given fixation. However, in both experiments, we found that in the saccadic reading condition a stronger alpha lateralization shortly before a saccade predicted shorter fixations on the subsequently fixated word. These results indicate that alpha lateralization can serve as a measure of attention deployment and its link to oculomotor behavior in reading. © 2017 Society for Psychophysiological Research.

A subanesthetic dose of ketamine in the Rhesus monkey reduces the occurrence of anticipatory saccades.

PubMed

Ameqrane, Ilhame; Ilhame, Ameqrane; Wattiez, Nicolas; Nicolas, Wattiez; Pouget, Pierre; Pierre, Pouget; Missal, Marcus; Marcus, Missal

2015-10-01

It has been shown that antagonism of the glutamatergic N-methyl-D-aspartate (NMDA) receptor with subanesthetic doses of ketamine perturbs the perception of elapsed time. Anticipatory eye movements are based on an internal representation of elapsed time. Therefore, the occurrence of anticipatory saccades could be a particularly sensitive indicator of abnormal time perception due to NMDA receptors blockade. The objective of this study was to determine whether the occurrence of anticipatory saccades could be selectively altered by a subanesthetic dose of ketamine. Three Rhesus monkeys were trained in a simple visually guided saccadic task with a variable delay. Monkeys were rewarded for making a visually guided saccade at the end of the delay. Premature anticipatory saccades to the future position of the eccentric target initiated before the end of the delay were not rewarded. A subanesthetic dose of ketamine (0.25 mg/kg) or a saline solution of the same volume was injected i.m. during the task. We found that the injected dose of ketamine did not induce sedation or abnormal behavior. However, in ∼4 min, ketamine induced a strong reduction of the occurrence of anticipatory saccades but did not reduce the occurrence of visually guided saccades. This unexpected reduction of anticipatory saccade occurrence could be interpreted as resulting from an altered use of the perception of elapsed time during the delay period induced by NMDA receptors antagonism.

Unconscious cues bias first saccades in a free-saccade task.

PubMed

Huang, Yu-Feng; Tan, Edlyn Gui Fang; Soon, Chun Siong; Hsieh, Po-Jang

2014-10-01

Visual-spatial attention can be biased towards salient visual information without visual awareness. It is unclear, however, whether such bias can further influence free-choices such as saccades in a free viewing task. In our experiment, we presented visual cues below awareness threshold immediately before people made free saccades. Our results showed that masked cues could influence the direction and latency of the first free saccade, suggesting that salient visual information can unconsciously influence free actions. Copyright © 2014 Elsevier Inc. All rights reserved.

Gender Classification Based on Eye Movements: A Processing Effect During Passive Face Viewing

PubMed Central

Sammaknejad, Negar; Pouretemad, Hamidreza; Eslahchi, Changiz; Salahirad, Alireza; Alinejad, Ashkan

2017-01-01

Studies have revealed superior face recognition skills in females, partially due to their different eye movement strategies when encoding faces. In the current study, we utilized these slight but important differences and proposed a model that estimates the gender of the viewers and classifies them into two subgroups, males and females. An eye tracker recorded participant’s eye movements while they viewed images of faces. Regions of interest (ROIs) were defined for each face. Results showed that the gender dissimilarity in eye movements was not due to differences in frequency of fixations in the ROI s per se. Instead, it was caused by dissimilarity in saccade paths between the ROIs. The difference enhanced when saccades were towards the eyes. Females showed significant increase in transitions from other ROI s to the eyes. Consequently, the extraction of temporal transient information of saccade paths through a transition probability matrix, similar to a first order Markov chain model, significantly improved the accuracy of the gender classification results. PMID:29071007

Gender Classification Based on Eye Movements: A Processing Effect During Passive Face Viewing.

PubMed

Sammaknejad, Negar; Pouretemad, Hamidreza; Eslahchi, Changiz; Salahirad, Alireza; Alinejad, Ashkan

2017-01-01

Studies have revealed superior face recognition skills in females, partially due to their different eye movement strategies when encoding faces. In the current study, we utilized these slight but important differences and proposed a model that estimates the gender of the viewers and classifies them into two subgroups, males and females. An eye tracker recorded participant's eye movements while they viewed images of faces. Regions of interest (ROIs) were defined for each face. Results showed that the gender dissimilarity in eye movements was not due to differences in frequency of fixations in the ROI s per se. Instead, it was caused by dissimilarity in saccade paths between the ROIs. The difference enhanced when saccades were towards the eyes. Females showed significant increase in transitions from other ROI s to the eyes. Consequently, the extraction of temporal transient information of saccade paths through a transition probability matrix, similar to a first order Markov chain model, significantly improved the accuracy of the gender classification results.

Deficiency of adaptive control of the binocular coordination of saccades in strabismus.

PubMed

Bucci, M P; Kapoula, Z; Eggert, T; Garraud, L

1997-10-01

Disconjugate (different in the two eyes) oculomotor adaptation is driven by the need to maintain binocular vision. Since binocular vision is deficient in strabismus, we wondered whether oculomotor disconjugate adaptive capabilities are deficient in such subjects. We studied eight adult subjects with constant, long-standing convergent strabismus of variable angles (4-30 prism D). No subject had severe amblyopia. Binocular vision was evaluated with stereoacuity tests. Two subjects had peripheral binocular vision and gross stereopsis; two other subjects had abnormal retinal correspondence and abnormal or pseudo gross stereopsis. In the other subjects binocular vision and stereopsis were absent. To stimulate disconjugate changes of saccades, subjects viewed for 20 min an image that was magnified in one eye (aniseikonia). Subjects with residual peripheral binocular vision and even subjects with pseudo or abnormal binocular vision showed disconjugate changes of the binocular coordination of their saccades; these changes reduced the disparity resulting from the aniseikonia. In contrast, for subjects without binocular vision the changes were not correlated with the disparity induced by the aniseikonia. Rather, these changes served to improve fixation of one or the other eye individually.

Micro and regular saccades across the lifespan during a visual search of "Where's Waldo" puzzles.

PubMed

Port, Nicholas L; Trimberger, Jane; Hitzeman, Steve; Redick, Bryan; Beckerman, Stephen

2016-01-01

Despite the fact that different aspects of visual-motor control mature at different rates and aging is associated with declines in both sensory and motor function, little is known about the relationship between microsaccades and either development or aging. Using a sample of 343 individuals ranging in age from 4 to 66 and a task that has been shown to elicit a high frequency of microsaccades (solving Where's Waldo puzzles), we explored microsaccade frequency and kinematics (main sequence curves) as a function of age. Taking advantage of the large size of our dataset (183,893 saccades), we also address (a) the saccade amplitude limit at which video eye trackers are able to accurately measure microsaccades and (b) the degree and consistency of saccade kinematics at varying amplitudes and directions. Using a modification of the Engbert-Mergenthaler saccade detector, we found that even the smallest amplitude movements (0.25-0.5°) demonstrate basic saccade kinematics. With regard to development and aging, both microsaccade and regular saccade frequency exhibited a very small increase across the life span. Visual search ability, as per many other aspects of visual performance, exhibited a U-shaped function over the lifespan. Finally, both large horizontal and moderate vertical directional biases were detected for all saccade sizes. Copyright © 2015 Elsevier Ltd. All rights reserved.

Linking express saccade occurance to stimulus properties and sensorimotor integration in the superior colliculus.

PubMed

Marino, Robert A; Levy, Ron; Munoz, Douglas P

2015-08-01

Express saccades represent the fastest possible eye movements to visual targets with reaction times that approach minimum sensory-motor conduction delays. Previous work in monkeys has identified two specific neural signals in the superior colliculus (SC: a midbrain sensorimotor integration structure involved in gaze control) that are required to execute express saccades: 1) previsual activity consisting of a low-frequency increase in action potentials in sensory-motor neurons immediately before the arrival of a visual response; and 2) a transient visual-sensory response consisting of a high-frequency burst of action potentials in visually responsive neurons resulting from the appearance of a visual target stimulus. To better understand how these two neural signals interact to produce express saccades, we manipulated the arrival time and magnitude of visual responses in the SC by altering target luminance and we examined the corresponding influences on SC activity and express saccade generation. We recorded from saccade neurons with visual-, motor-, and previsual-related activity in the SC of monkeys performing the gap saccade task while target luminance was systematically varied between 0.001 and 42.5 cd/m(2) against a black background (∼0.0001 cd/m(2)). Our results demonstrated that 1) express saccade latencies were linked directly to the arrival time in the SC of visual responses produced by abruptly appearing visual stimuli; 2) express saccades were generated toward both dim and bright targets whenever sufficient previsual activity was present; and 3) target luminance altered the likelihood of producing an express saccade. When an express saccade was generated, visuomotor neurons increased their activity immediately before the arrival of the visual response in the SC and saccade initiation. Furthermore, the visual and motor responses of visuomotor neurons merged into a single burst of action potentials, while the visual response of visual-only neurons was

Linking express saccade occurance to stimulus properties and sensorimotor integration in the superior colliculus

PubMed Central

Levy, Ron; Munoz, Douglas P.

2015-01-01

Express saccades represent the fastest possible eye movements to visual targets with reaction times that approach minimum sensory-motor conduction delays. Previous work in monkeys has identified two specific neural signals in the superior colliculus (SC: a midbrain sensorimotor integration structure involved in gaze control) that are required to execute express saccades: 1) previsual activity consisting of a low-frequency increase in action potentials in sensory-motor neurons immediately before the arrival of a visual response; and 2) a transient visual-sensory response consisting of a high-frequency burst of action potentials in visually responsive neurons resulting from the appearance of a visual target stimulus. To better understand how these two neural signals interact to produce express saccades, we manipulated the arrival time and magnitude of visual responses in the SC by altering target luminance and we examined the corresponding influences on SC activity and express saccade generation. We recorded from saccade neurons with visual-, motor-, and previsual-related activity in the SC of monkeys performing the gap saccade task while target luminance was systematically varied between 0.001 and 42.5 cd/m2 against a black background (∼0.0001 cd/m2). Our results demonstrated that 1) express saccade latencies were linked directly to the arrival time in the SC of visual responses produced by abruptly appearing visual stimuli; 2) express saccades were generated toward both dim and bright targets whenever sufficient previsual activity was present; and 3) target luminance altered the likelihood of producing an express saccade. When an express saccade was generated, visuomotor neurons increased their activity immediately before the arrival of the visual response in the SC and saccade initiation. Furthermore, the visual and motor responses of visuomotor neurons merged into a single burst of action potentials, while the visual response of visual-only neurons was

Algorithm for automatic analysis of electro-oculographic data

PubMed Central

2013-01-01

Background Large amounts of electro-oculographic (EOG) data, recorded during electroencephalographic (EEG) measurements, go underutilized. We present an automatic, auto-calibrating algorithm that allows efficient analysis of such data sets. Methods The auto-calibration is based on automatic threshold value estimation. Amplitude threshold values for saccades and blinks are determined based on features in the recorded signal. The performance of the developed algorithm was tested by analyzing 4854 saccades and 213 blinks recorded in two different conditions: a task where the eye movements were controlled (saccade task) and a task with free viewing (multitask). The results were compared with results from a video-oculography (VOG) device and manually scored blinks. Results The algorithm achieved 93% detection sensitivity for blinks with 4% false positive rate. The detection sensitivity for horizontal saccades was between 98% and 100%, and for oblique saccades between 95% and 100%. The classification sensitivity for horizontal and large oblique saccades (10 deg) was larger than 89%, and for vertical saccades larger than 82%. The duration and peak velocities of the detected horizontal saccades were similar to those in the literature. In the multitask measurement the detection sensitivity for saccades was 97% with a 6% false positive rate. Conclusion The developed algorithm enables reliable analysis of EOG data recorded both during EEG and as a separate metrics. PMID:24160372

Neurophysiology and Neuroanatomy of Reflexive and Voluntary Saccades in Non-Human Primates

ERIC Educational Resources Information Center

Johnston, Kevin; Everling, Stefan

2008-01-01

A multitude of cognitive functions can easily be tested by a number of relatively simple saccadic eye movement tasks. This approach has been employed extensively with patient populations to investigate the functional deficits associated with psychiatric disorders. Neurophysiological studies in non-human primates performing the same tasks have…

Visual and vestibular induced eye movements in verbal children and adults with autism

PubMed Central

Furman, Joseph M.; Osorio, Maria Joana; Minshew, Nancy J.

2016-01-01

This study investigated several types of eye movements that rely on the function of brainstem-cerebellar pathways specifically (vestibular-ocular reflexes) or on widely distributed pathways of the brain (horizontal pursuit and saccade eye movements). Although eye movements that rely on higher brain regions have been studies fairly extensively in autism, eye movements dependent on brainstem and cerebellum have not. This study involved 79 individuals with autism and 62 typical controls aged 5 to 52 years with IQ scores above 70. No differences between the autism and control groups were present on the measures of vestibular ocular reflexes, or on saccade velocity or accuracy. The autism group was significantly slower to initiate saccades, which was most prominent in the 8-18 year old age range. These findings provide the most substantial evidence to date of the functional integrity of brainstem and cerebellar pathways in autism, suggesting that the histopathological abnormalities described in these structures may not be associated with intrinsic dysfunction but rather reflect developmental alterations related to forebrain cortical systems formation. The increase in saccade latency adds to the substantial evidence of altered function and maturation of cortical systems in autism. Objective This study assessed the functionality of vestibular, pursuit and saccade circuitry in autism across a wide age range. Methods Subjects were 79 individuals with autism (AUT) and 62 controls (CON) aged 5 to 52 years with IQ scores > 70. For vestibular testing, earth-vertical axis rotation was performed in darkness and in a lighted visual surround with a fixation target. Ocular motor testing included assessment of horizontal saccades and horizontal smooth pursuit. Results No between-group differences were found in vestibular reflexes or in mean saccade velocity or accuracy. Saccade latency was increased in the AUT group with significant age-related effects in the 8-18 year old subgroups

Neural correlates of saccadic inhibition in healthy elderly and patients with amnestic mild cognitive impairment

PubMed Central

Alichniewicz, K. K.; Brunner, F.; Klünemann, H. H.; Greenlee, M. W.

2013-01-01

Performance on tasks that require saccadic inhibition declines with age and altered inhibitory functioning has also been reported in patients with Alzheimer's disease. Although mild cognitive impairment (MCI) is assumed to be a high-risk factor for conversion to AD, little is known about changes in saccadic inhibition and its neural correlates in this condition. Our study determined whether the neural activation associated with saccadic inhibition is altered in persons with amnestic mild cognitive impairment (aMCI). Functional magnetic resonance imaging (fMRI) revealed decreased activation in parietal lobe in healthy elderly persons compared to young persons and decreased activation in frontal eye fields in aMCI patients compared to healthy elderly persons during the execution of anti-saccades. These results illustrate that the decline in inhibitory functions is associated with impaired frontal activation in aMCI. This alteration in function might reflect early manifestations of AD and provide new insights in the neural activation changes that occur in pathological ageing. PMID:23898312

Spatial updating in area LIP is independent of saccade direction.

PubMed

Heiser, Laura M; Colby, Carol L

2006-05-01

We explore the world around us by making rapid eye movements to objects of interest. Remarkably, these eye movements go unnoticed, and we perceive the world as stable. Spatial updating is one of the neural mechanisms that contributes to this perception of spatial constancy. Previous studies in macaque lateral intraparietal cortex (area LIP) have shown that individual neurons update, or "remap," the locations of salient visual stimuli at the time of an eye movement. The existence of remapping implies that neurons have access to visual information from regions far beyond the classically defined receptive field. We hypothesized that neurons have access to information located anywhere in the visual field. We tested this by recording the activity of LIP neurons while systematically varying the direction in which a stimulus location must be updated. Our primary finding is that individual neurons remap stimulus traces in multiple directions, indicating that LIP neurons have access to information throughout the visual field. At the population level, stimulus traces are updated in conjunction with all saccade directions, even when we consider direction as a function of receptive field location. These results show that spatial updating in LIP is effectively independent of saccade direction. Our findings support the hypothesis that the activity of LIP neurons contributes to the maintenance of spatial constancy throughout the visual field.

The role of "rescue saccades" in tracking objects through occlusions.

PubMed

Zelinsky, Gregory J; Todor, Andrei

2010-12-29

We hypothesize that our ability to track objects through occlusions is mediated by timely assistance from gaze in the form of "rescue saccades"-eye movements to tracked objects that are in danger of being lost due to impending occlusion. Observers tracked 2-4 target sharks (out of 9) for 20 s as they swam through a rendered 3D underwater scene. Targets were either allowed to enter into occlusions (occlusion trials) or not (no occlusion trials). Tracking accuracy with 2-3 targets was ≥ 92% regardless of target occlusion but dropped to 74% on occlusion trials with four targets (no occlusion trials remained accurate; 83%). This pattern was mirrored in the frequency of rescue saccades. Rescue saccades accompanied approximatlely 50% of the Track 2-3 target occlusions, but only 34% of the Track 4 occlusions. Their frequency also decreased with increasing distance between a target and the nearest other object, suggesting that it is the potential for target confusion that summons a rescue saccade, not occlusion itself. These findings provide evidence for a tracking system that monitors for events that might cause track loss (e.g., occlusions) and requests help from the oculomotor system to resolve these momentary crises. As the number of crises increase with the number of targets, some requests for help go unsatisfied, resulting in degraded tracking.

Separate neural substrates in the human cerebellum for sensory-motor adaptation of reactive and of scanning voluntary saccades.

PubMed

Alahyane, N; Fonteille, V; Urquizar, C; Salemme, R; Nighoghossian, N; Pelisson, D; Tilikete, C

2008-01-01

Sensory-motor adaptation processes are critically involved in maintaining accurate motor behavior throughout life. Yet their underlying neural substrates and task-dependency bases are still poorly understood. We address these issues here by studying adaptation of saccadic eye movements, a well-established model of sensory-motor plasticity. The cerebellum plays a major role in saccadic adaptation but it has not yet been investigated whether this role can account for the known specificity of adaptation to the saccade type (e.g., reactive versus voluntary). Two patients with focal lesions in different parts of the cerebellum were tested using the double-step target paradigm. Each patient was submitted to two separate sessions: one for reactive saccades (RS) triggered by the sudden appearance of a visual target and the second for scanning voluntary saccades (SVS) performed when exploring a more complex scene. We found that a medial cerebellar lesion impaired adaptation of reactive-but not of voluntary-saccades, whereas a lateral lesion affected adaptation of scanning voluntary saccades, but not of reactive saccades. These findings provide the first evidence of an involvement of the lateral cerebellum in saccadic adaptation, and extend the demonstrated role of the cerebellum in RS adaptation to adaptation of SVS. The double dissociation of adaptive abilities is also consistent with our previous hypothesis of the involvement in saccadic adaptation of partially separated cerebellar areas specific to the reactive or voluntary task (Alahyane et al. Brain Res 1135:107-121 (2007)).

The Cerebellar Dysplasia of Chiari II Malformation as Revealed by Eye Movements

PubMed Central

Salman, Michael S.; Dennis, Maureen; Sharpe, James A.

2011-01-01

Introduction Chiari type II malformation (CII) is a developmental deformity of the hindbrain. We have previously reported that many patients with CII have impaired smooth pursuit, while few make inaccurate saccades or have an abnormal vestibulo-ocular reflex. In contrast, saccadic adaptation and visual fixation are normal. In this report, we correlate results from several eye movement studies with neuroimaging in CII. We present a model for structural changes within the cerebellum in CII. Methods Saccades, smooth pursuit, the vestibulo-ocular reflex, and visual fixation were recorded in 21 patients with CII, aged 8–19 years and 39 age-matched controls, using an infrared eye tracker. Qualitative and quantitative MRI data were correlated with eye movements in 19 CII patients and 28 controls. Results Nine patients with CII had abnormal eye movements. Smooth pursuit gain was subnormal in eight, saccadic accuracy abnormal in four, and vestibulo-ocular reflex gain abnormal in three. None had fixation instability. Patients with CII had a significantly smaller cerebellar volume than controls, and those with normal eye motion had an expanded midsagittal vermis compared to controls. However, patients with abnormal eye movements had a smaller (non-expanded) midsagittal vermis area, posterior fossa area and medial cerebellar volumes than CII patients with normal eye movements. Conclusions The deformity of CII affects the structure and function of the cerebellum selectively and differently in those with abnormal eye movements. We propose that the vermis can expand when compressed within a small posterior fossa in some CII patients, thus sparing its ocular motor functions. PMID:19960749

A Novel Saccadic Strategy Revealed by Suppression Head Impulse Testing of Patients with Bilateral Vestibular Loss.

PubMed

de Waele, Catherine; Shen, Qiwen; Magnani, Christophe; Curthoys, Ian S

2017-01-01

We examined the eye movement response patterns of a group of patients with bilateral vestibular loss (BVL) during suppression head impulse testing. Some showed a new saccadic strategy that may have potential for explaining how patients use saccades to recover from vestibular loss. Eight patients with severe BVL [vestibulo-ocular reflex (VOR) gains less than 0.35 and absent otolithic function] were tested. All patients were given the Dizziness Handicap Inventory and questioned about oscillopsia during abrupt head movements. Two paradigms of video head impulse testing of the horizontal VOR were used: (1) the classical head impulse paradigm [called head impulse test (HIMPs)]-fixating an earth-fixed target during the head impulse and (2) the new complementary test paradigm-fixating a head-fixed target during the head impulse (called SHIMPs). The VOR gain of HIMPs was quantified by two algorithms. During SHIMPs testing, some BVL patients consistently generated an inappropriate covert compensatory saccade during the head impulse that required a corresponding large anti-compensatory saccade at the end of the head impulse in order to obey the instructions to maintain gaze on the head-fixed target. By contrast, other BVL patients did not generate this inappropriate covert saccade and did not exhibit a corresponding anti-compensatory saccade. The latencies of the covert saccade in SHIMPs and HIMPs were similar. The pattern of covert saccades during SHIMPs appears to be related to the reduction of oscillopsia during abrupt head movements. BVL patients who did not report oscillopsia showed this unusual saccadic pattern, whereas BVL patients who reported oscillopsia did not show this pattern. This inappropriate covert SHIMPs saccade may be an objective indicator of how some patients with vestibular loss have learned to trigger covert saccades during head movements in everyday life.

Inferior Oblique Overaction: Anterior Transposition Versus Myectomy.

PubMed

Rajavi, Zhale; Feizi, Mohadeseh; Behradfar, Narges; Yaseri, Mehdi; Sayanjali, Shima; Motevaseli, Tahmine; Sabbaghi, Hamideh; Faghihi, Mohammad

2017-07-01

To compare the efficacy of inferior oblique myectomy and anterior transposition for correcting inferior oblique overaction (IOOA). This retrospective study was conducted on 56 patients with IOOA who had either myectomy or anterior transposition of the inferior oblique muscle from 2010 to 2015. The authors compared preoperative and postoperative inferior oblique muscle function grading (-4 to +4) as the main outcome measure and vertical and horizontal deviation, dissociated vertical deviation (DVD), and A- and V-pattern between the two surgical groups as secondary outcomes. A total of 99 eyes of 56 patients with a mean age of 5.9 ± 6.5 years were included (47 eyes in the myectomy group and 52 eyes in the anterior transposition group). There were no differences in preoperative best corrected visual acuity, amblyopia, spherical equivalent, and primary versus secondary IOOA between the two groups. Both surgical procedures were effective in reducing IOOA and satisfactory results were similar between the two groups: 61.7% and 67.3% in the myectomy and anterior transposition groups, respectively (P = .56). After adjustment for the preoperative DVD, there was no statistically significant difference between the two groups postoperatively. The preoperative hypertropia was 6 to 14 and 6 to 18 prism diopters (PD) in the myectomy and anterior transposition groups, respectively. After surgery, no patient had a vertical deviation greater than 5 PD. Both the inferior oblique myectomy and anterior transposition procedures are effective in reducing IOOA with similar satisfactory results. DVD and hypertropia were also corrected similarly by these two surgical procedures. [J Pediatr Ophthalmol Strabismus. 2017;54(4):232-237.]. Copyright 2017, SLACK Incorporated.

Secondary adaptation of memory-guided saccades

PubMed Central

Srimal, Riju; Curtis, Clayton E.

2011-01-01

Adaptation of saccade gains in response to errors keeps vision and action co-registered in the absence of awareness or effort. Timing is key, as the visual error must be available shortly after the saccade is generated or adaptation does not occur. Here, we tested the hypothesis that when feedback is delayed, learning still occurs, but does so through small secondary corrective saccades. Using a memory-guided saccade task, we gave feedback about the accuracy of saccades that was falsely displaced by a consistent amount, but only after long delays. Despite the delayed feedback, over time subjects improved in accuracy toward the false feedback. They did so not by adjusting their primary saccades, but via directed corrective saccades made before feedback was given. We propose that saccade learning may be driven by different types of feedback teaching signals. One teaching signal relies upon a tight temporal relation with the saccade and contributes to obligatory learning independent of awareness. When this signal is ineffective due to delayed error feedback, a second compensatory teaching signal enables flexible adjustments to the spatial goal of saccades and helps maintain sensorimotor accuracy. PMID:20803135

Monetary reward speeds up voluntary saccades.

PubMed

Chen, Lewis L; Chen, Y Mark; Zhou, Wu; Mustain, William D

2014-01-01

Past studies have shown that reward contingency is critical for sensorimotor learning, and reward expectation speeds up saccades in animals. Whether monetary reward speeds up saccades in human remains unknown. Here we addressed this issue by employing a conditional saccade task, in which human subjects performed a series of non-reflexive, visually-guided horizontal saccades. The subjects were (or were not) financially compensated for making a saccade in response to a centrally-displayed visual congruent (or incongruent) stimulus. Reward modulation of saccadic velocities was quantified independently of the amplitude-velocity coupling. We found that reward expectation significantly sped up voluntary saccades up to 30°/s, and the reward modulation was consistent across tests. These findings suggest that monetary reward speeds up saccades in human in a fashion analogous to how juice reward sped up saccades in monkeys. We further noticed that the idiosyncratic nasal-temporal velocity asymmetry was highly consistent regardless of test order, and its magnitude was not correlated with the magnitude of reward modulation. This suggests that reward modulation and the intrinsic velocity asymmetry may be governed by separate mechanisms that regulate saccade generation.

Saccade adaptation goes for the goal

PubMed Central

Madelain, Laurent; Herman, James P.; Harwood, Mark R.

2013-01-01

The oculomotor system maintains saccade accuracy by adjusting saccades that are consistently inaccurate. Four experiments were performed to determine the relative contribution of background and target postsaccadic displacement. Unlike typical saccade adaptation experiments, we used natural image scenes and masked target and background displacements during the saccade to exclude motion signals from allowing detection of the displacements. We found that the background had no effect on saccade gain while the target drove gain changes. Only when the target was blanked after the saccade did we observe some adaptation in the direction of the background displacement. We conclude that target selection is critical to saccade adaptation, and operates effectively against natural image backgrounds. PMID:23492925

The background is remapped across saccades.

PubMed

Cha, Oakyoon; Chong, Sang Chul

2014-02-01

Physiological studies have found that neurons prepare for impending eye movements, showing anticipatory responses to stimuli presented at the location of the post-saccadic receptive fields (RFs) (Wurtz in Vis Res 48:2070-2089, 2008). These studies proposed that visual neurons with shifting RFs prepared for the stimuli they would process after an impending saccade. Additionally, psychophysical studies have shown behavioral consequences of those anticipatory responses, including the transfer of aftereffects (Melcher in Nat Neurosci 10:903-907, 2007) and the remapping of attention (Rolfs et al. in Nat Neurosci 14:252-258, 2011). As the physiological studies proposed, the shifting RF mechanism explains the transfer of aftereffects. Recently, a new mechanism based on activation transfer via a saliency map was proposed, which accounted for the remapping of attention (Cavanagh et al. in Trends Cogn Sci 14:147-153, 2010). We hypothesized that there would be different aspects of the remapping corresponding to these different neural mechanisms. This study found that the information in the background was remapped to a similar extent as the figure, provided that the visual context remained stable. We manipulated the status of the figure and the ground in the saliency map and showed that the manipulation modulated the remapping of the figure and the ground in different ways. These results suggest that the visual system has an ability to remap the background as well as the figure, but lacks the ability to modulate the remapping of the background based on the visual context, and that different neural mechanisms might work together to maintain visual stability across saccades.

The parallel programming of voluntary and reflexive saccades.

PubMed

Walker, Robin; McSorley, Eugene

2006-06-01

A novel two-step paradigm was used to investigate the parallel programming of consecutive, stimulus-elicited ('reflexive') and endogenous ('voluntary') saccades. The mean latency of voluntary saccades, made following the first reflexive saccades in two-step conditions, was significantly reduced compared to that of voluntary saccades made in the single-step control trials. The latency of the first reflexive saccades was modulated by the requirement to make a second saccade: first saccade latency increased when a second voluntary saccade was required in the opposite direction to the first saccade, and decreased when a second saccade was required in the same direction as the first reflexive saccade. A second experiment confirmed the basic effect and also showed that a second reflexive saccade may be programmed in parallel with a first voluntary saccade. The results support the view that voluntary and reflexive saccades can be programmed in parallel on a common motor map.

Reliability and comparison of gain values with occurrence of saccades in the EyeSeeCam video head impulse test (vHIT).

PubMed

Korsager, Leise Elisabeth Hviid; Schmidt, Jesper Hvass; Faber, Christian; Wanscher, Jens Højberg

2016-12-01

The vHIT (video head impulse test) investigates the vestibular function in two ways: a VOR (vestibulo-ocular reflex) gain value and a head impulse diagram. From the diagram covert and overt saccades can be detected. Evaluation of the vestibular function based on vHIT depends on both parameters. There is a lack of knowledge regarding the reliability of the two parameters. The objective was to investigate the reliability of vHIT by comparing gain values between examiners on the same subjects, and to see how differences affected the occurrence of saccades. 25 subjects who had undergone cochlear implant (CI) surgery. Subjects were tested using the vHIT by two of four different examiners. Two judges interpreted the occurrence of saccades in the diagram. VOR gain values and the occurrence of saccades in the diagram. Differences in gain values between examiners varied from 0.2 to 0.58 with an average of 0.14 (95 % CI 0.12-0.16) on the right ear and 0.17 (95 % CI 0.15-0.19) on the left ear. Occurrences of saccades in the same patient were reproduced in 93 % of the cases by all examiners. Kappa's coefficient on the occurrence of saccades was 0.83. Interclass correlation coefficient (ICC) of the gain values between examiners ranged from 0.62 to 0.70. Differences in gain values amongst examiners did not seem to affect the occurrence of saccades in the same patient. The occurrence of saccades, therefore, seems to be more reliable than the gain value in the evaluation of the vestibular function. Interpretation of vHIT results should, therefore, first depend on the occurrence of saccades and second on the gain value.

Modification of saccadic gain by reinforcement

PubMed Central

Paeye, Céline; Wallman, Josh

2011-01-01

Control of saccadic gain is often viewed as a simple compensatory process in which gain is adjusted over many trials by the postsaccadic retinal error, thereby maintaining saccadic accuracy. Here, we propose that gain might also be changed by a reinforcement process not requiring a visual error. To test this hypothesis, we used experimental paradigms in which retinal error was removed by extinguishing the target at the start of each saccade and either an auditory tone or the vision of the target on the fovea was provided as reinforcement after those saccades that met an amplitude criterion. These reinforcement procedures caused a progressive change in saccade amplitude in nearly all subjects, although the rate of adaptation differed greatly among subjects. When we reversed the contingencies and reinforced those saccades landing closer to the original target location, saccade gain changed back toward normal gain in most subjects. When subjects had saccades adapted first by reinforcement and a week later by conventional intrasaccadic step adaptation, both paradigms yielded similar degrees of gain changes and similar transfer to new amplitudes and to new starting positions of the target step as well as comparable rates of recovery. We interpret these changes in saccadic gain in the absence of postsaccadic retinal error as showing that saccade adaptation is not controlled by a single error signal. More generally, our findings suggest that normal saccade adaptation might involve general learning mechanisms rather than only specialized mechanisms for motor calibration. PMID:21525366

Frames of reference for gaze saccades evoked during stimulation of lateral intraparietal cortex.

PubMed

Constantin, A G; Wang, H; Martinez-Trujillo, J C; Crawford, J D

2007-08-01

Previous studies suggest that stimulation of lateral intraparietal cortex (LIP) evokes saccadic eye movements toward eye- or head-fixed goals, whereas most single-unit studies suggest that LIP uses an eye-fixed frame with eye-position modulations. The goal of our study was to determine the reference frame for gaze shifts evoked during LIP stimulation in head-unrestrained monkeys. Two macaques (M1 and M2) were implanted with recording chambers over the right intraparietal sulcus and with search coils for recording three-dimensional eye and head movements. The LIP region was microstimulated using pulse trains of 300 Hz, 100-150 microA, and 200 ms. Eighty-five putative LIP sites in M1 and 194 putative sites in M2 were used in our quantitative analysis throughout this study. Average amplitude of the stimulation-evoked gaze shifts was 8.67 degrees for M1 and 7.97 degrees for M2 with very small head movements. When these gaze-shift trajectories were rotated into three coordinate frames (eye, head, and body), gaze endpoint distribution for all sites was most convergent to a common point when plotted in eye coordinates. Across all sites, the eye-centered model provided a significantly better fit compared with the head, body, or fixed-vector models (where the latter model signifies no modulation of the gaze trajectory as a function of initial gaze position). Moreover, the probability of evoking a gaze shift from any one particular position was modulated by the current gaze direction (independent of saccade direction). These results provide causal evidence that the motor commands from LIP encode gaze command in eye-fixed coordinates but are also subtly modulated by initial gaze position.

Eye movements during object recognition in visual agnosia.

PubMed

Charles Leek, E; Patterson, Candy; Paul, Matthew A; Rafal, Robert; Cristino, Filipe

2012-07-01

This paper reports the first ever detailed study about eye movement patterns during single object recognition in visual agnosia. Eye movements were recorded in a patient with an integrative agnosic deficit during two recognition tasks: common object naming and novel object recognition memory. The patient showed normal directional biases in saccades and fixation dwell times in both tasks and was as likely as controls to fixate within object bounding contour regardless of recognition accuracy. In contrast, following initial saccades of similar amplitude to controls, the patient showed a bias for short saccades. In object naming, but not in recognition memory, the similarity of the spatial distributions of patient and control fixations was modulated by recognition accuracy. The study provides new evidence about how eye movements can be used to elucidate the functional impairments underlying object recognition deficits. We argue that the results reflect a breakdown in normal functional processes involved in the integration of shape information across object structure during the visual perception of shape. Copyright © 2012 Elsevier Ltd. All rights reserved.

Updating visual memory across eye movements for ocular and arm motor control.

PubMed

Thompson, Aidan A; Henriques, Denise Y P

2008-11-01

Remembered object locations are stored in an eye-fixed reference frame, so that every time the eyes move, spatial representations must be updated for the arm-motor system to reflect the target's new relative position. To date, studies have not investigated how the brain updates these spatial representations during other types of eye movements, such as smooth-pursuit. Further, it is unclear what information is used in spatial updating. To address these questions we investigated whether remembered locations of pointing targets are updated following smooth-pursuit eye movements, as they are following saccades, and also investigated the role of visual information in estimating eye-movement amplitude for updating spatial memory. Misestimates of eye-movement amplitude were induced when participants visually tracked stimuli presented with a background that moved in either the same or opposite direction of the eye before pointing or looking back to the remembered target location. We found that gaze-dependent pointing errors were similar following saccades and smooth-pursuit and that incongruent background motion did result in a misestimate of eye-movement amplitude. However, the background motion had no effect on spatial updating for pointing, but did when subjects made a return saccade, suggesting that the oculomotor and arm-motor systems may rely on different sources of information for spatial updating.

Catch-up saccades in head-unrestrained conditions reveal that saccade amplitude is corrected using an internal model of target movement

PubMed Central

Daye, Pierre M.; Blohm, Gunnar; Lefèvre, Phillippe

2014-01-01

This study analyzes how human participants combine saccadic and pursuit gaze movements when they track an oscillating target moving along a randomly oriented straight line with the head free to move. We found that to track the moving target appropriately, participants triggered more saccades with increasing target oscillation frequency to compensate for imperfect tracking gains. Our sinusoidal paradigm allowed us to show that saccade amplitude was better correlated with internal estimates of position and velocity error at saccade onset than with those parameters 100 ms before saccade onset as head-restrained studies have shown. An analysis of saccadic onset time revealed that most of the saccades were triggered when the target was accelerating. Finally, we found that most saccades were triggered when small position errors were combined with large velocity errors at saccade onset. This could explain why saccade amplitude was better correlated with velocity error than with position error. Therefore, our results indicate that the triggering mechanism of head-unrestrained catch-up saccades combines position and velocity error at saccade onset to program and correct saccade amplitude rather than using sensory information 100 ms before saccade onset. PMID:24424378

EMDR Effects on Pursuit Eye Movements

PubMed Central

Kapoula, Zoi; Yang, Qing; Bonnet, Audrey; Bourtoire, Pauline; Sandretto, Jean

2010-01-01

This study aimed to objectivize the quality of smooth pursuit eye movements in a standard laboratory task before and after an Eye Movement Desensitization and Reprocessing (EMDR) session run on seven healthy volunteers. EMDR was applied on autobiographic worries causing moderate distress. The EMDR session was complete in 5 out of the 7 cases; distress measured by SUDS (Subjective Units of Discomfort Scale) decreased to a near zero value. Smooth pursuit eye movements were recorded by an Eyelink II video system before and after EMDR. For the five complete sessions, pursuit eye movement improved after their EMDR session. Notably, the number of saccade intrusions—catch-up saccades (CUS)—decreased and, reciprocally, there was an increase in the smooth components of the pursuit. Such an increase in the smoothness of the pursuit presumably reflects an improvement in the use of visual attention needed to follow the target accurately. Perhaps EMDR reduces distress thereby activating a cholinergic effect known to improve ocular pursuit. PMID:20505828

Eye movement sequence generation in humans: Motor or goal updating?

PubMed Central

Quaia, Christian; Joiner, Wilsaan M.; FitzGibbon, Edmond J.; Optican, Lance M.; Smith, Maurice A.

2011-01-01

Saccadic eye movements are often grouped in pre-programmed sequences. The mechanism underlying the generation of each saccade in a sequence is currently poorly understood. Broadly speaking, two alternative schemes are possible: first, after each saccade the retinotopic location of the next target could be estimated, and an appropriate saccade could be generated. We call this the goal updating hypothesis. Alternatively, multiple motor plans could be pre-computed, and they could then be updated after each movement. We call this the motor updating hypothesis. We used McLaughlin’s intra-saccadic step paradigm to artificially create a condition under which these two hypotheses make discriminable predictions. We found that in human subjects, when sequences of two saccades are planned, the motor updating hypothesis predicts the landing position of the second saccade in two-saccade sequences much better than the goal updating hypothesis. This finding suggests that the human saccadic system is capable of executing sequences of saccades to multiple targets by planning multiple motor commands, which are then updated by serial subtraction of ongoing motor output. PMID:21191134

Difference in Visual Processing Assessed by Eye Vergence Movements

PubMed Central

Solé Puig, Maria; Puigcerver, Laura; Aznar-Casanova, J. Antonio; Supèr, Hans

2013-01-01

Orienting visual attention is closely linked to the oculomotor system. For example, a shift of attention is usually followed by a saccadic eye movement and can be revealed by micro saccades. Recently we reported a novel role of another type of eye movement, namely eye vergence, in orienting visual attention. Shifts in visuospatial attention are characterized by the response modulation to a selected target. However, unlike (micro-) saccades, eye vergence movements do not carry spatial information (except for depth) and are thus not specific to a particular visual location. To further understand the role of eye vergence in visual attention, we tested subjects with different perceptual styles. Perceptual style refers to the characteristic way individuals perceive environmental stimuli, and is characterized by a spatial difference (local vs. global) in perceptual processing. We tested field independent (local; FI) and field dependent (global; FD) observers in a cue/no-cue task and a matching task. We found that FI observers responded faster and had stronger modulation in eye vergence in both tasks than FD subjects. The results may suggest that eye vergence modulation may relate to the trade-off between the size of spatial region covered by attention and the processing efficiency of sensory information. Alternatively, vergence modulation may have a role in the switch in cortical state to prepare the visual system for new incoming sensory information. In conclusion, vergence eye movements may be added to the growing list of functions of fixational eye movements in visual perception. However, further studies are needed to elucidate its role. PMID:24069140

Neuronal basis of covert spatial attention in the frontal eye field.

PubMed

Thompson, Kirk G; Biscoe, Keri L; Sato, Takashi R

2005-10-12

The influential "premotor theory of attention" proposes that developing oculomotor commands mediate covert visual spatial attention. A likely source of this attentional bias is the frontal eye field (FEF), an area of the frontal cortex involved in converting visual information into saccade commands. We investigated the link between FEF activity and covert spatial attention by recording from FEF visual and saccade-related neurons in monkeys performing covert visual search tasks without eye movements. Here we show that the source of attention signals in the FEF is enhanced activity of visually responsive neurons. At the time attention is allocated to the visual search target, nonvisually responsive saccade-related movement neurons are inhibited. Therefore, in the FEF, spatial attention signals are independent of explicit saccade command signals. We propose that spatially selective activity in FEF visually responsive neurons corresponds to the mental spotlight of attention via modulation of ongoing visual processing.

Saccadic Suppression of Flash Detection: the Uncertainty Theory VS. Alternative Theories.

NASA Astrophysics Data System (ADS)

Greenhouse, Daniel Stephen

Helmholtz('1) and others have proposed that when a saccadic eye movement occurs, stability of the visual world is maintained by a process that utilizes a corollary to the efferent motor signal for the eye movement, allowing the visual frame of reference to translate equal in magnitude, but opposite in sign, to the movement itself. This process is now known to be synchronous neither with the saccadic trajectory('2,3) nor in all parts of the visual field.('4) In addition, this process has been shown to have variability('2) whereby the perceived visual direction of a flash presented to a fixed retinal locus during a saccade may change from trial to trial. Hence, uncertainty with respect to visual location of a stimulus may exist during and just before a saccade. It has been established for normal vision that uncertainty produces a decline in detectability of a weak stimulus.('5,6,7) The research reported in this dissertation was performed to test the notion, first suggested by L. Matin,('8) that uncertainty is responsible for saccadic suppression, the decline in detectability that has been reported('9,10,11) for a brief flash presented during a saccade. After having established the existence of suppression under the conditions we employed (1(DEGREES) foveal flash occurring 2 1/2(DEGREES) into a 10(DEGREES) voluntary saccade, presented against an illuminated background) we conducted an initial test of the uncertainty theory. We employed a pedestal (flash at the spatial, temporal, and chromatic locus of the stimulus, occurring on all trials, and sufficiently intense as to be visible during saccades) in an attempt to reduce uncertainty. Suppression was nearly eliminated for all subjects. We interpreted this result in terms of the uncertainty theory, but were unable to reject alternative theories of suppression, which include forms of neural inhibition,('10,11) increaed noise level in the retina during saccades,('12) and metacontrast masking.('13). The next experiment

Changes to online control and eye-hand coordination with healthy ageing.

PubMed

O'Rielly, Jessica L; Ma-Wyatt, Anna

2018-06-01

Goal directed movements are typically accompanied by a saccade to the target location. Online control plays an important part in correction of a reach, especially if the target or goal of the reach moves during the reach. While there are notable changes to visual processing and motor control with healthy ageing, there is limited evidence about how eye-hand coordination during online updating changes with healthy ageing. We sought to quantify differences between older and younger people for eye-hand coordination during online updating. Participants completed a double step reaching task implemented under time pressure. The target perturbation could occur 200, 400 and 600 ms into a reach. We measured eye position and hand position throughout the trials to investigate changes to saccade latency, movement latency, movement time, reach characteristics and eye-hand latency and accuracy. Both groups were able to update their reach in response to a target perturbation that occurred at 200 or 400 ms into the reach. All participants demonstrated incomplete online updating for the 600 ms perturbation time. Saccade latencies, measured from the first target presentation, were generally longer for older participants. Older participants had significantly increased movement times but there was no significant difference between groups for touch accuracy. We speculate that the longer movement times enable the use of new visual information about the target location for online updating towards the end of the movement. Interestingly, older participants also produced a greater proportion of secondary saccades within the target perturbation condition and had generally shorter eye-hand latencies. This is perhaps a compensatory mechanism as there was no significant group effect on final saccade accuracy. Overall, the pattern of results suggests that online control of movements may be qualitatively different in older participants. Crown Copyright © 2018. Published by Elsevier B.V. All

Immaturity of the Oculomotor Saccade and Vergence Interaction in Dyslexic Children: Evidence from a Reading and Visual Search Study

PubMed Central

Bucci, Maria Pia; Nassibi, Naziha; Gerard, Christophe-Loic; Bui-Quoc, Emmanuel; Seassau, Magali

2012-01-01

Studies comparing binocular eye movements during reading and visual search in dyslexic children are, at our knowledge, inexistent. In the present study we examined ocular motor characteristics in dyslexic children versus two groups of non dyslexic children with chronological/reading age-matched. Binocular eye movements were recorded by an infrared system (mobileEBT®, e(ye)BRAIN) in twelve dyslexic children (mean age 11 years old) and a group of chronological age-matched (N = 9) and reading age-matched (N = 10) non dyslexic children. Two visual tasks were used: text reading and visual search. Independently of the task, the ocular motor behavior in dyslexic children is similar to those reported in reading age-matched non dyslexic children: many and longer fixations as well as poor quality of binocular coordination during and after the saccades. In contrast, chronological age-matched non dyslexic children showed a small number of fixations and short duration of fixations in reading task with respect to visual search task; furthermore their saccades were well yoked in both tasks. The atypical eye movement's patterns observed in dyslexic children suggest a deficiency in the visual attentional processing as well as an immaturity of the ocular motor saccade and vergence systems interaction. PMID:22438934

Visuomotor mental rotation of a saccade: The contingent negative variation scales to the angle of rotation.

PubMed

Heath, Matthew; Colino, Francisco L; Chan, Jillian; Krigolson, Olave E

2018-02-01

The visuomotor mental rotation (VMR) of a saccade requires a response to a region of space that is dissociated from a stimulus by a pre-specified angle, and work has shown a monotonic increase in reaction times as a function of increasing oblique angles of rotation. These results have been taken as evidence of a continuous process of rotation and have generated competing hypotheses. One hypothesis asserts that rotation is mediated via frontoparietal structures, whereas a second states that a continuous shift in the activity of direction-specific neurons in the superior colliculus (SC) supports rotation. Research to date, however, has not examined the neural mechanisms underlying VMR saccades and both hypotheses therefore remain untested. The present study measured the behavioural data and event-related brain potentials (ERP) of standard (i.e., 0° of rotation) and VMR saccades involving 35°, 70° and 105° of rotation. Behavioural results showed that participants adhered to task-based rotation demands and ERP findings showed that the amplitude of the contingent negative variation (CNV) linearly decreased with increasing angle of rotation. The cortical generators of the CNV are linked to frontoparietal structures supporting movement preparation. Although our ERP design does not allow us to exclude a possible role of the SC in the rotation of a VMR saccade, they do demonstrate that such actions are supported by a continuous and cortically based rotation process. Copyright © 2017 Elsevier Ltd. All rights reserved.

Strength of figure-ground activity in monkey primary visual cortex predicts saccadic reaction time in a delayed detection task.

PubMed

Supèr, Hans; Lamme, Victor A F

2007-06-01

When and where are decisions made? In the visual system a saccade, which is a fast shift of gaze toward a target in the visual scene, is the behavioral outcome of a decision. Current neurophysiological data and reaction time models show that saccadic reaction times are determined by a build-up of activity in motor-related structures, such as the frontal eye fields. These structures depend on the sensory evidence of the stimulus. Here we use a delayed figure-ground detection task to show that late modulated activity in the visual cortex (V1) predicts saccadic reaction time. This predictive activity is part of the process of figure-ground segregation and is specific for the saccade target location. These observations indicate that sensory signals are directly involved in the decision of when and where to look.

Secondary (micro-)saccades: the influence of primary saccade end point and target eccentricity on the process of postsaccadic fixation.

PubMed

Ohl, Sven; Brandt, Stephan A; Kliegl, Reinhold

2011-12-08

We examine how the size of saccadic under-/overshoot and target eccentricity influence the latency, amplitude and orientation of secondary (micro-)saccades. In our experiment, a target appeared at an eccentricity of either 6° or 14° of visual angle. Subjects were instructed to direct their gaze as quickly as possible to the target and hold fixation at the new location until the end of the trial. Typically, increasing saccadic error is associated with faster and larger secondary saccades. We show that secondary saccades at distant in contrast to close targets have in a specific error range a shorter latency, larger amplitude, and follow more often the direction of the primary saccade. Finally, we demonstrate that an undershooting primary saccade is followed almost exclusively by secondary saccades into the same direction while overshooting primary saccades are followed by secondary saccades into both directions. This supports the notion that under- and overshooting imply different consequences for postsaccadic oculomotor processing. Results are discussed using a model, introduced by Rolfs, Kliegl, and Engbert (2008), to account for the generation of microsaccades. We argue that the dynamic interplay of target eccentricity and the magnitude of the saccadic under-/overshoot can be explained by a different strength of activation in the two hemispheres of the saccadic motor map in this model. Copyright © 2011 Elsevier Ltd. All rights reserved.

Distinct eye movement patterns enhance dynamic visual acuity

PubMed Central

Palidis, Dimitrios J.; Wyder-Hodge, Pearson A.; Fooken, Jolande; Spering, Miriam

2017-01-01

Dynamic visual acuity (DVA) is the ability to resolve fine spatial detail in dynamic objects during head fixation, or in static objects during head or body rotation. This ability is important for many activities such as ball sports, and a close relation has been shown between DVA and sports expertise. DVA tasks involve eye movements, yet, it is unclear which aspects of eye movements contribute to successful performance. Here we examined the relation between DVA and the kinematics of smooth pursuit and saccadic eye movements in a cohort of 23 varsity baseball players. In a computerized dynamic-object DVA test, observers reported the location of the gap in a small Landolt-C ring moving at various speeds while eye movements were recorded. Smooth pursuit kinematics—eye latency, acceleration, velocity gain, position error—and the direction and amplitude of saccadic eye movements were linked to perceptual performance. Results reveal that distinct eye movement patterns—minimizing eye position error, tracking smoothly, and inhibiting reverse saccades—were related to dynamic visual acuity. The close link between eye movement quality and DVA performance has important implications for the development of perceptual training programs to improve DVA. PMID:28187157

Effects of Peripheral Visual Field Loss on Eye Movements During Visual Search

PubMed Central

Wiecek, Emily; Pasquale, Louis R.; Fiser, Jozsef; Dakin, Steven; Bex, Peter J.

2012-01-01

Natural vision involves sequential eye movements that bring the fovea to locations selected by peripheral vision. How peripheral visual field loss (PVFL) affects this process is not well understood. We examine how the location and extent of PVFL affects eye movement behavior in a naturalistic visual search task. Ten patients with PVFL and 13 normally sighted subjects with full visual fields (FVF) completed 30 visual searches monocularly. Subjects located a 4° × 4° target, pseudo-randomly selected within a 26° × 11° natural image. Eye positions were recorded at 50 Hz. Search duration, fixation duration, saccade size, and number of saccades per trial were not significantly different between PVFL and FVF groups (p > 0.1). A χ2 test showed that the distributions of saccade directions for PVFL and FVL subjects were significantly different in 8 out of 10 cases (p < 0.01). Humphrey Visual Field pattern deviations for each subject were compared with the spatial distribution of eye movement directions. There were no significant correlations between saccade directional bias and visual field sensitivity across the 10 patients. Visual search performance was not significantly affected by PVFL. An analysis of eye movement directions revealed patients with PVFL show a biased directional distribution that was not directly related to the locus of vision loss, challenging feed-forward models of eye movement control. Consequently, many patients do not optimally compensate for visual field loss during visual search. PMID:23162511

Animal spotting in Alzheimer's disease: an eye tracking study of object categorization.

PubMed

Boucart, Muriel; Bubbico, Giovanna; Szaffarczyk, Sébastien; Pasquier, Florence

2014-01-01

We investigated rapid object categorization and, more specifically, the ability to detect a target object within a natural scene in people with mild Alzheimer's disease (AD) using a saccadic choice task. It has been suggested that the anatomical pathway likely used to initiate rapid oculomotor responses in the saccadic choice task could involve the Frontal Eye Field, a structure that is part of the dorsal attentional network, in which connectivity is disrupted in AD. Seventeen patients with mild AD and 23 healthy age-matched controls took part in the study. A group of 24 young healthy observers was included as it has been reported that normal aging affects eye movements. Participants were presented with pairs of colored photographs of natural scenes, one containing an animal (the target) and one containing various objects (distracter), displayed for 1 s left and right of fixation. They were asked to saccade to the scene containing an animal. Neither pathology nor age affected temporal (saccade latencies and durations) and spatial (saccade amplitude) parameters of eye movements. Patients with AD were significantly less accurate than age-matched controls, and older participants were less accurate than young observers. The results are interpreted in terms of noisier sensory information and increased uncertainty in relation to deficits in the magnocellular pathway. The results suggest that, even at a mild stage of the pathology, people exhibit difficulties in selecting relevant objects.

A laser-based eye-tracking system.

PubMed

Irie, Kenji; Wilson, Bruce A; Jones, Richard D; Bones, Philip J; Anderson, Tim J

2002-11-01

This paper reports on the development of a new eye-tracking system for noninvasive recording of eye movements. The eye tracker uses a flying-spot laser to selectively image landmarks on the eye and, subsequently, measure horizontal, vertical, and torsional eye movements. Considerable work was required to overcome the adverse effects of specular reflection of the flying-spot from the surface of the eye onto the sensing elements of the eye tracker. These effects have been largely overcome, and the eye-tracker has been used to document eye movement abnormalities, such as abnormal torsional pulsion of saccades, in the clinical setting.

Basal Ganglia Neuronal Activity during Scanning Eye Movements in Parkinson’s Disease

PubMed Central

Sieger, Tomáš; Bonnet, Cecilia; Serranová, Tereza; Wild, Jiří; Novák, Daniel; Růžička, Filip; Urgošík, Dušan; Růžička, Evžen; Gaymard, Bertrand; Jech, Robert

2013-01-01

The oculomotor role of the basal ganglia has been supported by extensive evidence, although their role in scanning eye movements is poorly understood. Nineteen Parkinsońs disease patients, which underwent implantation of deep brain stimulation electrodes, were investigated with simultaneous intraoperative microelectrode recordings and single channel electrooculography in a scanning eye movement task by viewing a series of colored pictures selected from the International Affective Picture System. Four patients additionally underwent a visually guided saccade task. Microelectrode recordings were analyzed selectively from the subthalamic nucleus, substantia nigra pars reticulata and from the globus pallidus by the WaveClus program which allowed for detection and sorting of individual neurons. The relationship between neuronal firing rate and eye movements was studied by crosscorrelation analysis. Out of 183 neurons that were detected, 130 were found in the subthalamic nucleus, 30 in the substantia nigra and 23 in the globus pallidus. Twenty percent of the neurons in each of these structures showed eye movement-related activity. Neurons related to scanning eye movements were mostly unrelated to the visually guided saccades. We conclude that a relatively large number of basal ganglia neurons are involved in eye motion control. Surprisingly, neurons related to scanning eye movements differed from neurons activated during saccades suggesting functional specialization and segregation of both systems for eye movement control. PMID:24223158

Evaluating camouflage design using eye movement data.

PubMed

Lin, Chiuhsiang Joe; Chang, Chi-Chan; Lee, Yung-Hui

2014-05-01

This study investigates the characteristics of eye movements during a camouflaged target search task. Camouflaged targets were randomly presented on two natural landscapes. The performance of each camouflage design was assessed by target detection hit rate, detection time, number of fixations on display, first saccade amplitude to target, number of fixations on target, fixation duration on target, and subjective ratings of search task difficulty. The results showed that the camouflage patterns could significantly affect the eye-movement behavior, especially first saccade amplitude and fixation duration, and the findings could be used to increase the sensitivity of the camouflage assessment. We hypothesized that the assessment could be made with regard to the differences in detectability and discriminability of the camouflage patterns. These could explain less efficient search behavior in eye movements. Overall, data obtained from eye movements can be used to significantly enhance the interpretation of the effects of different camouflage design. Copyright © 2013 Elsevier Ltd and The Ergonomics Society. All rights reserved.

White matter fiber integrity of the saccadic eye movement network differs between schizophrenia and healthy groups.

PubMed

Schaeffer, David J; Rodrigue, Amanda L; Burton, Courtney R; Pierce, Jordan E; Murphy, Megan N; Clementz, Brett A; McDowell, Jennifer E

2017-12-01

Recent diffusion tensor imaging (DTI) studies suggest that altered white matter fiber integrity is a pathophysiological feature of schizophrenia. Lower white matter integrity is associated with poor cognitive control, a characteristic of schizophrenia that can be measured using antisaccade tasks. Although the functional neural correlates of poor antisaccade performance have been well documented, fewer studies have investigated the extent to which white matter fibers connecting the functional nodes of this network contribute to antisaccade performance. The aim of the present study was to assess the white matter structural integrity of fibers connecting two functional nodes (putamen and medial frontal eye fields) of the saccadic eye movement network implicated in poor antisaccade performance in schizophrenia. To evaluate white matter integrity, DTI was acquired on subjects with schizophrenia and two comparison groups: (a) behaviorally matched healthy comparison subjects with low levels of cognitive control (LCC group), and (b) healthy subjects with high levels of cognitive control (HCC group). White matter fibers were tracked between functional regions of interest generated from antisaccade fMRI activation maps, and measures of diffusivity were quantified. The results demonstrated lower white matter integrity in the schizophrenia group than in the HCC group, but not the LCC group who showed similarly poor cognitive control performance. Overall, the results suggest that these alterations are not specific to the disease process of schizophrenia, but may rather be a function of uncontrolled cognitive factors that are concomitant with the disease but also observed in some healthy people. © 2017 Society for Psychophysiological Research.

The influence of artificial scotomas on eye movements during visual search.

PubMed

Cornelissen, Frans W; Bruin, Klaas J; Kooijman, Aart C

2005-01-01

Fixation durations are normally adapted to the difficulty of the foveal analysis task. We examine to what extent artificial central and peripheral visual field defects interfere with this adaptation process. Subjects performed a visual search task while their eye movements were registered. The latter were used to drive a real-time gaze-dependent display that was used to create artificial central and peripheral visual field defects. Recorded eye movements were used to determine saccadic amplitude, number of fixations, fixation durations, return saccades, and changes in saccade direction. For central defects, although fixation duration increased with the size of the absolute central scotoma, this increase was too small to keep recognition performance optimal, evident from an associated increase in the rate of return saccades. Providing a relatively small amount of visual information in the central scotoma did substantially reduce subjects' search times but not their fixation durations. Surprisingly, reducing the size of the tunnel also prolonged fixation duration for peripheral defects. This manipulation also decreased the rate of return saccades, suggesting that the fixations were prolonged beyond the duration required by the foveal task. Although we find that adaptation of fixation duration to task difficulty clearly occurs in the presence of artificial scotomas, we also find that such field defects may render the adaptation suboptimal for the task at hand. Thus, visual field defects may not only hinder vision by limiting what the subject sees of the environment but also by limiting the visual system's ability to program efficient eye movements. We speculate this is because of how visual field defects bias the balance between saccade generation and fixation stabilization.

Evaluation of the Tobii EyeX Eye tracking controller and Matlab toolkit for research.

PubMed

Gibaldi, Agostino; Vanegas, Mauricio; Bex, Peter J; Maiello, Guido

2017-06-01

The Tobii Eyex Controller is a new low-cost binocular eye tracker marketed for integration in gaming and consumer applications. The manufacturers claim that the system was conceived for natural eye gaze interaction, does not require continuous recalibration, and allows moderate head movements. The Controller is provided with a SDK to foster the development of new eye tracking applications. We review the characteristics of the device for its possible use in scientific research. We develop and evaluate an open source Matlab Toolkit that can be employed to interface with the EyeX device for gaze recording in behavioral experiments. The Toolkit provides calibration procedures tailored to both binocular and monocular experiments, as well as procedures to evaluate other eye tracking devices. The observed performance of the EyeX (i.e. accuracy < 0.6°, precision < 0.25°, latency < 50 ms and sampling frequency ≈55 Hz), is sufficient for some classes of research application. The device can be successfully employed to measure fixation parameters, saccadic, smooth pursuit and vergence eye movements. However, the relatively low sampling rate and moderate precision limit the suitability of the EyeX for monitoring micro-saccadic eye movements or for real-time gaze-contingent stimulus control. For these applications, research grade, high-cost eye tracking technology may still be necessary. Therefore, despite its limitations with respect to high-end devices, the EyeX has the potential to further the dissemination of eye tracking technology to a broad audience, and could be a valuable asset in consumer and gaming applications as well as a subset of basic and clinical research settings.

Persistence in eye movement during visual search

NASA Astrophysics Data System (ADS)

Amor, Tatiana A.; Reis, Saulo D. S.; Campos, Daniel; Herrmann, Hans J.; Andrade, José S.

2016-02-01

As any cognitive task, visual search involves a number of underlying processes that cannot be directly observed and measured. In this way, the movement of the eyes certainly represents the most explicit and closest connection we can get to the inner mechanisms governing this cognitive activity. Here we show that the process of eye movement during visual search, consisting of sequences of fixations intercalated by saccades, exhibits distinctive persistent behaviors. Initially, by focusing on saccadic directions and intersaccadic angles, we disclose that the probability distributions of these measures show a clear preference of participants towards a reading-like mechanism (geometrical persistence), whose features and potential advantages for searching/foraging are discussed. We then perform a Multifractal Detrended Fluctuation Analysis (MF-DFA) over the time series of jump magnitudes in the eye trajectory and find that it exhibits a typical multifractal behavior arising from the sequential combination of saccades and fixations. By inspecting the time series composed of only fixational movements, our results reveal instead a monofractal behavior with a Hurst exponent , which indicates the presence of long-range power-law positive correlations (statistical persistence). We expect that our methodological approach can be adopted as a way to understand persistence and strategy-planning during visual search.

Changes in Simple Spike Activity of some Purkinje cells in the Oculomotor Vermis during Saccade Adaptation are Appropriate to Participate in Motor Learning

PubMed Central

Kojima, Yoshiko; Soetedjo, Robijanto; Fuchs, Albert F.

2010-01-01

Adaptation of saccadic eye movements provides an excellent motor learning model to study theories of neuronal plasticity. When primates make saccades to a jumping target, a backward step of the target during the saccade can make it appear to overshoot. If this deception continues for many trials, saccades gradually decrease in amplitude to go directly to the back-stepped target location. We used this adaptation paradigm to evaluate the Marr-Albus hypothesis that such motor learning occurs at the Purkinje (P-) cell of the cerebellum. We recorded the activity of identified P-cells in the oculomotor vermis, lobules VIc and VII. After determining the on and off error directions of a P-cell’s complex spike activity, we determined whether its saccade-related simple spike (SS) activity changed during saccade adaptation in those two directions. Before adaptation, 57 of 61 P-cells exhibited a clear burst, pause or a combination of both for saccades in one or both directions. Sixty-two percent of all cells, including 2 of the 4 initially unresponsive ones, behaved differently for saccades whose size changed because of adaptation than for saccades of similar sizes gathered before adaptation. In at least 42% of these, the changes were appropriate to decrease saccade amplitude based on our current knowledge of cerebellum and brain stem saccade circuitry. Changes in activity during adaptation were not compensating for the potential fatigue associated with performing many saccades. Therefore, many P-cells in the oculomotor vermis exhibit changes in SS activity specific to adapted saccades and therefore appropriate to induce adaptation. PMID:20220005

The Role of Saccade Targeting in the Transsaccadic Integration of Object Types and Tokens

ERIC Educational Resources Information Center

Gajewski, Daniel A.; Henderson, John M.

2005-01-01

The presence of location-dependent and location-independent benefits on object identification in an eye movement contingent preview paradigm has been taken as support for the transsaccadic integration of object types and object tokens (J. M. Henderson, 1994). A recent study, however, suggests a critical role for saccade targeting in the generation…

Influence of social presence on eye movements in visual search tasks.

PubMed

Liu, Na; Yu, Ruifeng

2017-12-01

This study employed an eye-tracking technique to investigate the influence of social presence on eye movements in visual search tasks. A total of 20 male subjects performed visual search tasks in a 2 (target presence: present vs. absent) × 2 (task complexity: complex vs. simple) × 2 (social presence: alone vs. a human audience) within-subject experiment. Results indicated that the presence of an audience could evoke a social facilitation effect on response time in visual search tasks. Compared with working alone, the participants made fewer and shorter fixations, larger saccades and shorter scan path in simple search tasks and more and longer fixations, smaller saccades and longer scan path in complex search tasks when working with an audience. The saccade velocity and pupil diameter in the audience-present condition were larger than those in the working-alone condition. No significant change in target fixation number was observed between two social presence conditions. Practitioner Summary: This study employed an eye-tracking technique to examine the influence of social presence on eye movements in visual search tasks. Results clarified the variation mechanism and characteristics of oculomotor scanning induced by social presence in visual search.

Testing a simplified method for measuring velocity integration in saccades using a manipulation of target contrast.

PubMed

Etchells, Peter J; Benton, Christopher P; Ludwig, Casimir J H; Gilchrist, Iain D

2011-01-01

A growing number of studies in vision research employ analyses of how perturbations in visual stimuli influence behavior on single trials. Recently, we have developed a method along such lines to assess the time course over which object velocity information is extracted on a trial-by-trial basis in order to produce an accurate intercepting saccade to a moving target. Here, we present a simplified version of this methodology, and use it to investigate how changes in stimulus contrast affect the temporal velocity integration window used when generating saccades to moving targets. Observers generated saccades to one of two moving targets which were presented at high (80%) or low (7.5%) contrast. In 50% of trials, target velocity stepped up or down after a variable interval after the saccadic go signal. The extent to which the saccade endpoint can be accounted for as a weighted combination of the pre- or post-step velocities allows for identification of the temporal velocity integration window. Our results show that the temporal integration window takes longer to peak in the low when compared to high contrast condition. By enabling the assessment of how information such as changes in velocity can be used in the programming of a saccadic eye movement on single trials, this study describes and tests a novel methodology with which to look at the internal processing mechanisms that transform sensory visual inputs into oculomotor outputs.

Brain processing of visual information during fast eye movements maintains motor performance.

PubMed

Panouillères, Muriel; Gaveau, Valérie; Socasau, Camille; Urquizar, Christian; Pélisson, Denis

2013-01-01

Movement accuracy depends crucially on the ability to detect errors while actions are being performed. When inaccuracies occur repeatedly, both an immediate motor correction and a progressive adaptation of the motor command can unfold. Of all the movements in the motor repertoire of humans, saccadic eye movements are the fastest. Due to the high speed of saccades, and to the impairment of visual perception during saccades, a phenomenon called "saccadic suppression", it is widely believed that the adaptive mechanisms maintaining saccadic performance depend critically on visual error signals acquired after saccade completion. Here, we demonstrate that, contrary to this widespread view, saccadic adaptation can be based entirely on visual information presented during saccades. Our results show that visual error signals introduced during saccade execution--by shifting a visual target at saccade onset and blanking it at saccade offset--induce the same level of adaptation as error signals, presented for the same duration, but after saccade completion. In addition, they reveal that this processing of intra-saccadic visual information for adaptation depends critically on visual information presented during the deceleration phase, but not the acceleration phase, of the saccade. These findings demonstrate that the human central nervous system can use short intra-saccadic glimpses of visual information for motor adaptation, and they call for a reappraisal of current models of saccadic adaptation.

Electrical Microstimulation of the Pulvinar Biases Saccade Choices and Reaction Times in a Time-Dependent Manner

PubMed Central

2017-01-01

The pulvinar complex is interconnected extensively with brain regions involved in spatial processing and eye movement control. Recent inactivation studies have shown that the dorsal pulvinar (dPul) plays a role in saccade target selection; however, it remains unknown whether it exerts effects on visual processing or at planning/execution stages. We used electrical microstimulation of the dPul while monkeys performed saccade tasks toward instructed and freely chosen targets. Timing of stimulation was varied, starting before, at, or after onset of target(s). Stimulation affected saccade properties and target selection in a time-dependent manner. Stimulation starting before but overlapping with target onset shortened saccadic reaction times (RTs) for ipsiversive (to the stimulation site) target locations, whereas stimulation starting at and after target onset caused systematic delays for both ipsiversive and contraversive locations. Similarly, stimulation starting before the onset of bilateral targets increased ipsiversive target choices, whereas stimulation after target onset increased contraversive choices. Properties of dPul neurons and stimulation effects were consistent with an overall contraversive drive, with varying outcomes contingent upon behavioral demands. RT and choice effects were largely congruent in the visually-guided task, but stimulation during memory-guided saccades, while influencing RTs and errors, did not affect choice behavior. Together, these results show that the dPul plays a primary role in action planning as opposed to visual processing, that it exerts its strongest influence on spatial choices when decision and action are temporally close, and that this choice effect can be dissociated from motor effects on saccade initiation and execution. SIGNIFICANCE STATEMENT Despite a recent surge of interest, the core function of the pulvinar, the largest thalamic complex in primates, remains elusive. This understanding is crucial given the central

Suppression of displacement detection in the presence and absence of eye movements: a neuro-computational perspective.

PubMed

Bergelt, Julia; Hamker, Fred H

2016-02-01

Understanding the subjective experience of a visually stable world during eye movements has been an important research topic for many years. Various studies were conducted to reveal fundamental mechanisms of this phenomenon. For example, in the paradigm saccadic suppression of displacement (SSD), it has been observed that a small displacement of a saccade target could not easily be reported if this displacement took place during a saccade. New results from Zimmermann et al. (J Neurophysiol 112(12):3066-3076, 2014) show that the effect of being oblivious to small displacements occurs not only during saccades, but also if a mask is introduced while the target is displaced. We address the question of how neurons in the parietal cortex may be connected to each other to account for the SSD effect in experiments involving a saccade and equally well in the absence of an eye movement while perception is disrupted by a mask.

Multimodal assessment of visual attention using the Bethesda Eye & Attention Measure (BEAM).

PubMed

Ettenhofer, Mark L; Hershaw, Jamie N; Barry, David M

2016-01-01

Computerized cognitive tests measuring manual response time (RT) and errors are often used in the assessment of visual attention. Evidence suggests that saccadic RT and errors may also provide valuable information about attention. This study was conducted to examine a novel approach to multimodal assessment of visual attention incorporating concurrent measurements of saccadic eye movements and manual responses. A computerized cognitive task, the Bethesda Eye & Attention Measure (BEAM) v.34, was designed to evaluate key attention networks through concurrent measurement of saccadic and manual RT and inhibition errors. Results from a community sample of n = 54 adults were analyzed to examine effects of BEAM attention cues on manual and saccadic RT and inhibition errors, internal reliability of BEAM metrics, relationships between parallel saccadic and manual metrics, and relationships of BEAM metrics to demographic characteristics. Effects of BEAM attention cues (alerting, orienting, interference, gap, and no-go signals) were consistent with previous literature examining key attention processes. However, corresponding saccadic and manual measurements were weakly related to each other, and only manual measurements were related to estimated verbal intelligence or years of education. This study provides preliminary support for the feasibility of multimodal assessment of visual attention using the BEAM. Results suggest that BEAM saccadic and manual metrics provide divergent measurements. Additional research will be needed to obtain comprehensive normative data, to cross-validate BEAM measurements with other indicators of neural and cognitive function, and to evaluate the utility of these metrics within clinical populations of interest.

MR-eyetracker: a new method for eye movement recording in functional magnetic resonance imaging.

PubMed

Kimmig, H; Greenlee, M W; Huethe, F; Mergner, T

1999-06-01

We present a method for recording saccadic and pursuit eye movements in the magnetic resonance tomograph designed for visual functional magnetic resonance imaging (fMRI) experiments. To reliably classify brain areas as pursuit or saccade related it is important to carefully measure the actual eye movements. For this purpose, infrared light, created outside the scanner by light-emitting diodes (LEDs), is guided via optic fibers into the head coil and onto the eye of the subject. Two additional fiber optical cables pick up the light reflected by the iris. The illuminating and detecting cables are mounted in a plastic eyepiece that is manually lowered to the level of the eye. By means of differential amplification, we obtain a signal that covaries with the horizontal position of the eye. Calibration of eye position within the scanner yields an estimate of eye position with a resolution of 0.2 degrees at a sampling rate of 1000 Hz. Experiments are presented that employ echoplanar imaging with 12 image planes through visual, parietal and frontal cortex while subjects performed saccadic and pursuit eye movements. The distribution of BOLD (blood oxygen level dependent) responses is shown to depend on the type of eye movement performed. Our method yields high temporal and spatial resolution of the horizontal component of eye movements during fMRI scanning. Since the signal is purely optical, there is no interaction between the eye movement signals and the echoplanar images. This reasonably priced eye tracker can be used to control eye position and monitor eye movements during fMRI.

Short-term adaptation of the VOR: non-retinal-slip error signals and saccade substitution

NASA Technical Reports Server (NTRS)

Eggers, Sscott D Z.; De Pennington, Nick; Walker, Mark F.; Shelhamer, Mark; Zee, David S.

2003-01-01

We studied short-term (30 min) adaptation of the vestibulo-ocular reflex (VOR) in five normal humans using a "position error" stimulus without retinal image motion. Both before and after adaptation a velocity gain (peak slow-phase eye velocity/peak head velocity) and a position gain (total eye movement during chair rotation/amplitude of chair motion) were measured in darkness using search coils. The vestibular stimulus was a brief ( approximately 700 ms), 15 degrees chair rotation in darkness (peak velocity 43 degrees /s). To elicit adaptation, a straight-ahead fixation target disappeared during chair movement and when the chair stopped the target reappeared at a new location in front of the subject for gain-decrease (x0) adaptation, or 10 degrees opposite to chair motion for gain-increase (x1.67) adaptation. This position-error stimulus was effective at inducing VOR adaptation, though for gain-increase adaptation the primary strategy was to substitute augmenting saccades during rotation while for gain-decrease adaptation both corrective saccades and a decrease in slow-phase velocity occurred. Finally, the presence of the position-error signal alone, at the end of head rotation, without any attempt to fix upon it, was not sufficient to induce adaptation. Adaptation did occur, however, if the subject did make a saccade to the target after head rotation, or even if the subject paid attention to the new location of the target without actually looking at it.

One algorithm to rule them all? An evaluation and discussion of ten eye movement event-detection algorithms.

PubMed

Andersson, Richard; Larsson, Linnea; Holmqvist, Kenneth; Stridh, Martin; Nyström, Marcus

2017-04-01

Almost all eye-movement researchers use algorithms to parse raw data and detect distinct types of eye movement events, such as fixations, saccades, and pursuit, and then base their results on these. Surprisingly, these algorithms are rarely evaluated. We evaluated the classifications of ten eye-movement event detection algorithms, on data from an SMI HiSpeed 1250 system, and compared them to manual ratings of two human experts. The evaluation focused on fixations, saccades, and post-saccadic oscillations. The evaluation used both event duration parameters, and sample-by-sample comparisons to rank the algorithms. The resulting event durations varied substantially as a function of what algorithm was used. This evaluation differed from previous evaluations by considering a relatively large set of algorithms, multiple events, and data from both static and dynamic stimuli. The main conclusion is that current detectors of only fixations and saccades work reasonably well for static stimuli, but barely better than chance for dynamic stimuli. Differing results across evaluation methods make it difficult to select one winner for fixation detection. For saccade detection, however, the algorithm by Larsson, Nyström and Stridh (IEEE Transaction on Biomedical Engineering, 60(9):2484-2493,2013) outperforms all algorithms in data from both static and dynamic stimuli. The data also show how improperly selected algorithms applied to dynamic data misestimate fixation and saccade properties.

Contribution of the frontal eye field to gaze shifts in the head-unrestrained rhesus monkey: neuronal activity.

PubMed

Knight, T A

2012-12-06

The frontal eye field (FEF) has a strong influence on saccadic eye movements with the head restrained. With the head unrestrained, eye saccades combine with head movements to produce large gaze shifts, and microstimulation of the FEF evokes both eye and head movements. To test whether the dorsomedial FEF provides commands for the entire gaze shift or its separate eye and head components, we recorded extracellular single-unit activity in monkeys trained to make large head-unrestrained gaze shifts. We recorded 80 units active during gaze shifts, and closely examined 26 of these that discharged a burst of action potentials that preceded horizontal gaze movements. These units were movement or visuomovement related and most exhibited open movement fields with respect to amplitude. To reveal the relations of burst parameters to gaze, eye, and/or head movement metrics, we used behavioral dissociations of gaze, eye, and head movements and linear regression analyses. The burst number of spikes (NOS) was strongly correlated with movement amplitude and burst temporal parameters were strongly correlated with movement temporal metrics for eight gaze-related burst neurons and five saccade-related burst neurons. For the remaining 13 neurons, the NOS was strongly correlated with the head movement amplitude, but burst temporal parameters were most strongly correlated with eye movement temporal metrics (head-eye-related burst neurons, HEBNs). These results suggest that FEF units do not encode a command for the unified gaze shift only; instead, different units may carry signals related to the overall gaze shift or its eye and/or head components. Moreover, the HEBNs exhibit bursts whose magnitude and timing may encode a head displacement signal and a signal that influences the timing of the eye saccade, thereby serving as a mechanism for coordinating the eye and head movements of a gaze shift. Copyright © 2012 IBRO. Published by Elsevier Ltd. All rights reserved.

Saccade frequency response to visual cues during gait in Parkinson's disease: the selective role of attention.

PubMed

Stuart, Samuel; Lord, Sue; Galna, Brook; Rochester, Lynn

2018-04-01

Gait impairment is a core feature of Parkinson's disease (PD) with implications for falls risk. Visual cues improve gait in PD, but the underlying mechanisms are unclear. Evidence suggests that attention and vision play an important role; however, the relative contribution from each is unclear. Measurement of visual exploration (specifically saccade frequency) during gait allows for real-time measurement of attention and vision. Understanding how visual cues influence visual exploration may allow inferences of the underlying mechanisms to response which could help to develop effective therapeutics. This study aimed to examine saccade frequency during gait in response to a visual cue in PD and older adults and investigate the roles of attention and vision in visual cue response in PD. A mobile eye-tracker measured saccade frequency during gait in 55 people with PD and 32 age-matched controls. Participants walked in a straight line with and without a visual cue (50 cm transverse lines) presented under single task and dual-task (concurrent digit span recall). Saccade frequency was reduced when walking in PD compared to controls; however, visual cues ameliorated saccadic deficit. Visual cues significantly increased saccade frequency in both PD and controls under both single task and dual-task. Attention rather than visual function was central to saccade frequency and gait response to visual cues in PD. In conclusion, this study highlights the impact of visual cues on visual exploration when walking and the important role of attention in PD. Understanding these complex features will help inform intervention development. © 2018 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.

Eye Tracking Metrics for Workload Estimation in Flight Deck Operation

NASA Technical Reports Server (NTRS)

Ellis, Kyle; Schnell, Thomas

2010-01-01

Flight decks of the future are being enhanced through improved avionics that adapt to both aircraft and operator state. Eye tracking allows for non-invasive analysis of pilot eye movements, from which a set of metrics can be derived to effectively and reliably characterize workload. This research identifies eye tracking metrics that correlate to aircraft automation conditions, and identifies the correlation of pilot workload to the same automation conditions. Saccade length was used as an indirect index of pilot workload: Pilots in the fully automated condition were observed to have on average, larger saccadic movements in contrast to the guidance and manual flight conditions. The data set itself also provides a general model of human eye movement behavior and so ostensibly visual attention distribution in the cockpit for approach to land tasks with various levels of automation, by means of the same metrics used for workload algorithm development.

A review on eye movement studies in childhood and adolescent psychiatry.

PubMed

Rommelse, Nanda N J; Van der Stigchel, Stefan; Sergeant, Joseph A

2008-12-01

The neural substrates of eye movement measures are largely known. Therefore, measurement of eye movements in psychiatric disorders may provide insight into the underlying neuropathology of these disorders. Visually guided saccades, antisaccades, memory guided saccades, and smooth pursuit eye movements will be reviewed in various childhood psychiatric disorders. The four aims of this review are (1) to give a thorough overview of eye movement studies in a wide array of psychiatric disorders occurring during childhood and adolescence (attention-deficit/hyperactivity disorder, oppositional deviant disorder and conduct disorder, autism spectrum disorders, reading disorder, childhood-onset schizophrenia, Tourette's syndrome, obsessive compulsive disorder, and anxiety and depression), (2) to discuss the specificity and overlap of eye movement findings across disorders and paradigms, (3) to discuss the developmental aspects of eye movement abnormalities in childhood and adolescence psychiatric disorders, and (4) to present suggestions for future research. In order to make this review of interest to a broad audience, attention will be given to the clinical manifestation of the disorders and the theoretical background of the eye movement paradigms.

Object form discontinuity facilitates displacement discrimination across saccades.

PubMed

Demeyer, Maarten; De Graef, Peter; Wagemans, Johan; Verfaillie, Karl

2010-06-01

Stimulus displacements coinciding with a saccadic eye movement are poorly detected by human observers. In recent years, converging evidence has shown that this phenomenon does not result from poor transsaccadic retention of presaccadic stimulus position information, but from the visual system's efforts to spatially align presaccadic and postsaccadic perception on the basis of visual landmarks. It is known that this process can be disrupted, and transsaccadic displacement detection performance can be improved, by briefly blanking the stimulus display during and immediately after the saccade. In the present study, we investigated whether this improvement could also follow from a discontinuity in the task-irrelevant form of the displaced stimulus. We observed this to be the case: Subjects more accurately identified the direction of intrasaccadic displacements when the displaced stimulus simultaneously changed form, compared to conditions without a form change. However, larger improvements were still observed under blanking conditions. In a second experiment, we show that facilitation induced by form changes and blanks can combine. We conclude that a strong assumption of visual stability underlies the suppression of transsaccadic change detection performance, the rejection of which generalizes from stimulus form to stimulus position.

[A tracking function of human eye in microgravity and during readaptation to earth's gravity].

PubMed

Kornilova, L N

2001-01-01

The paper summarizes results of electro-oculography of all ways of visual tracking: fixative eye movements (saccades), smooth pursuit of linearly, pendulum-like and circularly moving point stimuli, pursuit of vertically moving foveoretinal optokinetic stimuli, and presents values of thresholds and amplification coefficients of the optokinetic nystagmus during tracking of linear movement of foveoretinal optokinetic stimuli. Investigations were performed aboard the Salyut and Mir space stations with participation of 31 cosmonauts of whom 27 made long-term (76 up to 438 day) and 4 made short-term (7 to 9 day) missions. It was shown that in space flight the saccadic structure within the tracking reaction does not change; yet, corrective movements (additional microsaccades to achieve tracking) appeared in 47% of observations at the onset and in 76% of observations on months 3 to 6 of space flight. After landing, the structure of vertical saccades was found altered in half the cosmonauts. No matter in or after flight, reverse nystagmus was present along with the gaze nystagmus during static saccades in 22% (7 cosmonauts) of the observations. Amplitude of tracking vertically, diagonally or circularly moving stimuli was significantly reduced as period on mission increased. Early in flight (40% of the cosmonauts) and shortly afterwards (21% of the cosmonauts) the structure of smooth tracking reaction was totally broken up, that is eye followed stimulus with micro- or macrosaccades. The structure of smooth eye tracking recovered on flight days 6-8 and on postflight days 3-4. However, in 46% of the cosmonauts on long-term missions the structure of smooth eye tracking was noted to be disturbed periodically, i.e. smooth tracking was replaced by saccadic.

Effects of aging on eye movements in the real world

PubMed Central

Dowiasch, Stefan; Marx, Svenja; Einhäuser, Wolfgang; Bremmer, Frank

2015-01-01

The effects of aging on eye movements are well studied in the laboratory. Increased saccade latencies or decreased smooth-pursuit gain are well established findings. The question remains whether these findings are influenced by the rather untypical environment of a laboratory; that is, whether or not they transfer to the real world. We measured 34 healthy participants between the age of 25 and 85 during two everyday tasks in the real world: (I) walking down a hallway with free gaze, (II) visual tracking of an earth-fixed object while walking straight-ahead. Eye movements were recorded with a mobile light-weight eye tracker, the EyeSeeCam (ESC). We find that age significantly influences saccade parameters. With increasing age, saccade frequency, amplitude, peak velocity, and mean velocity are reduced and the velocity/amplitude distribution as well as the velocity profile become less skewed. In contrast to laboratory results on smooth pursuit, we did not find a significant effect of age on tracking eye-movements in the real world. Taken together, age-related eye-movement changes as measured in the laboratory only partly resemble those in the real world. It is well-conceivable that in the real world additional sensory cues, such as head-movement or vestibular signals, may partially compensate for age-related effects, which, according to this view, would be specific to early motion processing. In any case, our results highlight the importance of validity for natural situations when studying the impact of aging on real-life performance. PMID:25713524

Effects of aging on eye movements in the real world.

PubMed

Dowiasch, Stefan; Marx, Svenja; Einhäuser, Wolfgang; Bremmer, Frank

2015-01-01

The effects of aging on eye movements are well studied in the laboratory. Increased saccade latencies or decreased smooth-pursuit gain are well established findings. The question remains whether these findings are influenced by the rather untypical environment of a laboratory; that is, whether or not they transfer to the real world. We measured 34 healthy participants between the age of 25 and 85 during two everyday tasks in the real world: (I) walking down a hallway with free gaze, (II) visual tracking of an earth-fixed object while walking straight-ahead. Eye movements were recorded with a mobile light-weight eye tracker, the EyeSeeCam (ESC). We find that age significantly influences saccade parameters. With increasing age, saccade frequency, amplitude, peak velocity, and mean velocity are reduced and the velocity/amplitude distribution as well as the velocity profile become less skewed. In contrast to laboratory results on smooth pursuit, we did not find a significant effect of age on tracking eye-movements in the real world. Taken together, age-related eye-movement changes as measured in the laboratory only partly resemble those in the real world. It is well-conceivable that in the real world additional sensory cues, such as head-movement or vestibular signals, may partially compensate for age-related effects, which, according to this view, would be specific to early motion processing. In any case, our results highlight the importance of validity for natural situations when studying the impact of aging on real-life performance.

Bridging the Gap: Understanding Eye Movements and Attentional Mechanisms is Key to Improving Amblyopia Treatment

NASA Astrophysics Data System (ADS)

Gambacorta, Christina Grace

Amblyopia is a developmental visual disorder resulting in sensory, motor and attentional deficits, including delays in both saccadic and manual reaction time. It is unclear whether this delay is due to differences in sensory processing of the stimulus, or the processes required to dis-engage/shift/re-engage attention when moving the eye from fixation to a saccadic target. In the first experiment we compare asymptotic saccadic and manual reaction times between the two eyes, using equivalent stimulus strength to account for differences in sensory processing. In a follow-up study, we modulate RT by removing the fixation dot, which is thought to release spatial attention at the fovea, and reduces reaction time in normal observers. Finally, we discuss the implications for these findings on future amblyopic treatment, specifically dichoptic video game playing. Playing videogames may help engage the attentional network, leading to greater improvements than traditional treatment of patching the non- amblyopic eye. Further, when treatment involves both eyes, fixation stability may be improved during the therapeutic intervention, yielding a better outcome than just playing a video game with a patch over the non-amblyopic eye.

Numerical simulation of nonlinear feedback model of saccade generation circuit implemented in the LabView graphical programming language.

PubMed

Jackson, M E; Gnadt, J W

1999-03-01

The object-oriented graphical programming language LabView was used to implement the numerical solution to a computational model of saccade generation in primates. The computational model simulates the activity and connectivity of anatomical strictures known to be involved in saccadic eye movements. The LabView program provides a graphical user interface to the model that makes it easy to observe and modify the behavior of each element of the model. Essential elements of the source code of the LabView program are presented and explained. A copy of the model is available for download from the internet.

Eye Movement Abnormalities in Joubert Syndrome

PubMed Central

Weiss, Avery H.; Doherty, Dan; Parisi, Melissa; Shaw, Dennis; Glass, Ian; Phillips, James O.

2011-01-01

Purpose Joubert syndrome is a genetic disorder characterized by hypoplasia of the midline cerebellum and deficiency of crossed connections between neural structures in the brain stem that control eye movements. The goal of the study was to quantify the eye movement abnormalities that occur in Joubert syndrome. Methods Eye movements were recorded in response to stationary stimuli and stimuli designed to elicit smooth pursuit, saccades, optokinetic nystagmus (OKN), vestibulo-ocular reflex (VOR), and vergence using video-oculography or Skalar search coils in 8 patients with Joubert syndrome. All patients underwent high-resolution magnetic resonance imaging (MRI). Results All patients had the highly characteristic molar tooth sign on brain MRI. Six patients had conjugate pendular (n = 4) or see-saw nystagmus (n = 2); gaze holding was stable in four patients. Smooth-pursuit gains were 0.28 to 1.19, 0.11 to 0.68, and 0.33 to 0.73 at peak stimulus velocities of 10, 20, and 30 deg/s in six patients; smooth pursuit could not be elicited in four patients. Saccade gains in five patients ranged from 0.35 to 0.91 and velocities ranged from 60.9 to 259.5 deg/s. Targeted saccades could not be elicited in five patients. Horizontal OKN gain was uniformly reduced across gratings drifted at velocities of 15, 30, and 45 deg/s. VOR gain was 0.8 or higher and phase appropriate in three of seven subjects; VOR gain was 0.3 or less and phase was indeterminate in four subjects. Conclusions The abnormalities in gaze-holding and eye movements are consistent with the distributed abnormalities of midline cerebellum and brain stem regions associated with Joubert syndrome. PMID:19443711

Dynamics of attentional deployment during saccadic programming.

PubMed

Castet, Eric; Jeanjean, Sébastien; Montagnini, Anna; Laugier, Danièle; Masson, Guillaume S

2006-03-03

The dynamics of attentional deployment before saccade execution was studied with a dual-task paradigm. Observers made a horizontal saccade whose direction was indicated by a symbolic precue and had to discriminate the orientation of a Gabor patch displayed at different delays after the precue (but before saccade onset). The patch location relative to the saccadic target was indicated to observers before each block. Therefore, on each trial, observers were informed simultaneously about the respective absolute locations of the saccadic and perceptual targets. The main result is that orientational acuity improved over a period of 150-200 ms after the precue onset at the saccadic target location, where overall performance is best, and at distant locations. This effect is due to attentional factors rather than to an alerting effect. It is also dependent on the efficiency of the temporal masks displayed before and after the Gabor patches.

Eye Movement Training and Suggested Gaze Strategies in Tunnel Vision - A Randomized and Controlled Pilot Study.

PubMed

Ivanov, Iliya V; Mackeben, Manfred; Vollmer, Annika; Martus, Peter; Nguyen, Nhung X; Trauzettel-Klosinski, Susanne

2016-01-01

Degenerative retinal diseases, especially retinitis pigmentosa (RP), lead to severe peripheral visual field loss (tunnel vision), which impairs mobility. The lack of peripheral information leads to fewer horizontal eye movements and, thus, diminished scanning in RP patients in a natural environment walking task. This randomized controlled study aimed to improve mobility and the dynamic visual field by applying a compensatory Exploratory Saccadic Training (EST). Oculomotor responses during walking and avoiding obstacles in a controlled environment were studied before and after saccade or reading training in 25 RP patients. Eye movements were recorded using a mobile infrared eye tracker (Tobii glasses) that measured a range of spatial and temporal variables. Patients were randomly assigned to two training conditions: Saccade (experimental) and reading (control) training. All subjects who first performed reading training underwent experimental training later (waiting list control group). To assess the effect of training on subjects, we measured performance in the training task and the following outcome variables related to daily life: Response Time (RT) during exploratory saccade training, Percent Preferred Walking Speed (PPWS), the number of collisions with obstacles, eye position variability, fixation duration, and the total number of fixations including the ones in the subjects' blind area of the visual field. In the saccade training group, RTs on average decreased, while the PPWS significantly increased. The improvement persisted, as tested 6 weeks after the end of the training. On average, the eye movement range of RP patients before and after training was similar to that of healthy observers. In both, the experimental and reading training groups, we found many fixations outside the subjects' seeing visual field before and after training. The average fixation duration was significantly shorter after the training, but only in the experimental training condition

Eye Movement Training and Suggested Gaze Strategies in Tunnel Vision - A Randomized and Controlled Pilot Study

PubMed Central

Ivanov, Iliya V.; Mackeben, Manfred; Vollmer, Annika; Martus, Peter; Nguyen, Nhung X.; Trauzettel-Klosinski, Susanne

2016-01-01

Purpose Degenerative retinal diseases, especially retinitis pigmentosa (RP), lead to severe peripheral visual field loss (tunnel vision), which impairs mobility. The lack of peripheral information leads to fewer horizontal eye movements and, thus, diminished scanning in RP patients in a natural environment walking task. This randomized controlled study aimed to improve mobility and the dynamic visual field by applying a compensatory Exploratory Saccadic Training (EST). Methods Oculomotor responses during walking and avoiding obstacles in a controlled environment were studied before and after saccade or reading training in 25 RP patients. Eye movements were recorded using a mobile infrared eye tracker (Tobii glasses) that measured a range of spatial and temporal variables. Patients were randomly assigned to two training conditions: Saccade (experimental) and reading (control) training. All subjects who first performed reading training underwent experimental training later (waiting list control group). To assess the effect of training on subjects, we measured performance in the training task and the following outcome variables related to daily life: Response Time (RT) during exploratory saccade training, Percent Preferred Walking Speed (PPWS), the number of collisions with obstacles, eye position variability, fixation duration, and the total number of fixations including the ones in the subjects' blind area of the visual field. Results In the saccade training group, RTs on average decreased, while the PPWS significantly increased. The improvement persisted, as tested 6 weeks after the end of the training. On average, the eye movement range of RP patients before and after training was similar to that of healthy observers. In both, the experimental and reading training groups, we found many fixations outside the subjects' seeing visual field before and after training. The average fixation duration was significantly shorter after the training, but only in the

Role of expected reward in frontal eye field during natural scene search

PubMed Central

Lawlor, Patrick N.; Ramkumar, Pavan; Kording, Konrad P.; Segraves, Mark A.

2016-01-01

When a saccade is expected to result in a reward, both neural activity in oculomotor areas and the saccade itself (e.g., its vigor and latency) are altered (compared with when no reward is expected). As such, it is unclear whether the correlations of neural activity with reward indicate a representation of reward beyond a movement representation; the modulated neural activity may simply represent the differences in motor output due to expected reward. Here, to distinguish between these possibilities, we trained monkeys to perform a natural scene search task while we recorded from the frontal eye field (FEF). Indeed, when reward was expected (i.e., saccades to the target), FEF neurons showed enhanced responses. Moreover, when monkeys accidentally made eye movements to the target, firing rates were lower than when they purposively moved to the target. Thus, neurons were modulated by expected reward rather than simply the presence of the target. We then fit a model that simultaneously included components related to expected reward and saccade parameters. While expected reward led to shorter latency and higher velocity saccades, these behavioral changes could not fully explain the increased FEF firing rates. Thus, FEF neurons appear to encode motivational factors such as reward expectation, above and beyond the kinematic and behavioral consequences of imminent reward. PMID:27169506

Real-time estimation of horizontal gaze angle by saccade integration using in-ear electrooculography.

PubMed

Hládek, Ľuboš; Porr, Bernd; Brimijoin, W Owen

2018-01-01

The manuscript proposes and evaluates a real-time algorithm for estimating eye gaze angle based solely on single-channel electrooculography (EOG), which can be obtained directly from the ear canal using conductive ear moulds. In contrast to conventional high-pass filtering, we used an algorithm that calculates absolute eye gaze angle via statistical analysis of detected saccades. The estimated eye positions of the new algorithm were still noisy. However, the performance in terms of Pearson product-moment correlation coefficients was significantly better than the conventional approach in some instances. The results suggest that in-ear EOG signals captured with conductive ear moulds could serve as a basis for light-weight and portable horizontal eye gaze angle estimation suitable for a broad range of applications. For instance, for hearing aids to steer the directivity of microphones in the direction of the user's eye gaze.

Looking for ideas: Eye behavior during goal-directed internally focused cognition☆

PubMed Central

Walcher, Sonja; Körner, Christof; Benedek, Mathias

2017-01-01

Humans have a highly developed visual system, yet we spend a high proportion of our time awake ignoring the visual world and attending to our own thoughts. The present study examined eye movement characteristics of goal-directed internally focused cognition. Deliberate internally focused cognition was induced by an idea generation task. A letter-by-letter reading task served as external task. Idea generation (vs. reading) was associated with more and longer blinks and fewer microsaccades indicating an attenuation of visual input. Idea generation was further associated with more and shorter fixations, more saccades and saccades with higher amplitudes as well as heightened stimulus-independent variation of eye vergence. The latter results suggest a coupling of eye behavior to internally generated information and associated cognitive processes, i.e. searching for ideas. Our results support eye behavior patterns as indicators of goal-directed internally focused cognition through mechanisms of attenuation of visual input and coupling of eye behavior to internally generated information. PMID:28689088

Eye movements reveal epistemic curiosity in human observers.

PubMed

Baranes, Adrien; Oudeyer, Pierre-Yves; Gottlieb, Jacqueline

2015-12-01

Saccadic (rapid) eye movements are primary means by which humans and non-human primates sample visual information. However, while saccadic decisions are intensively investigated in instrumental contexts where saccades guide subsequent actions, it is largely unknown how they may be influenced by curiosity - the intrinsic desire to learn. While saccades are sensitive to visual novelty and visual surprise, no study has examined their relation to epistemic curiosity - interest in symbolic, semantic information. To investigate this question, we tracked the eye movements of human observers while they read trivia questions and, after a brief delay, were visually given the answer. We show that higher curiosity was associated with earlier anticipatory orienting of gaze toward the answer location without changes in other metrics of saccades or fixations, and that these influences were distinct from those produced by variations in confidence and surprise. Across subjects, the enhancement of anticipatory gaze was correlated with measures of trait curiosity from personality questionnaires. Finally, a machine learning algorithm could predict curiosity in a cross-subject manner, relying primarily on statistical features of the gaze position before the answer onset and independently of covariations in confidence or surprise, suggesting potential practical applications for educational technologies, recommender systems and research in cognitive sciences. With this article, we provide full access to the annotated database allowing readers to reproduce the results. Epistemic curiosity produces specific effects on oculomotor anticipation that can be used to read out curiosity states. Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.

Feature-binding errors after eye movements and shifts of attention.

PubMed

Golomb, Julie D; L'heureux, Zara E; Kanwisher, Nancy

2014-05-01

When people move their eyes, the eye-centered (retinotopic) locations of objects must be updated to maintain world-centered (spatiotopic) stability. Here, we demonstrated that the attentional-updating process temporarily distorts the fundamental ability to bind object locations with their features. Subjects were simultaneously presented with four colors after a saccade-one in a precued spatiotopic target location-and were instructed to report the target's color using a color wheel. Subjects' reports were systematically shifted in color space toward the color of the distractor in the retinotopic location of the cue. Probabilistic modeling exposed both crude swapping errors and subtler feature mixing (as if the retinotopic color had blended into the spatiotopic percept). Additional experiments conducted without saccades revealed that the two types of errors stemmed from different attentional mechanisms (attention shifting vs. splitting). Feature mixing not only reflects a new perceptual phenomenon, but also provides novel insight into how attention is remapped across saccades.

Decoding of intended saccade direction in an oculomotor brain-computer interface

NASA Astrophysics Data System (ADS)

Jia, Nan; Brincat, Scott L.; Salazar-Gómez, Andrés F.; Panko, Mikhail; Guenther, Frank H.; Miller, Earl K.

2017-08-01

Objective. To date, invasive brain-computer interface (BCI) research has largely focused on replacing lost limb functions using signals from the hand/arm areas of motor cortex. However, the oculomotor system may be better suited to BCI applications involving rapid serial selection from spatial targets, such as choosing from a set of possible words displayed on a computer screen in an augmentative and alternative communication (AAC) application. Here we aimed to demonstrate the feasibility of a BCI utilizing the oculomotor system. Approach. We developed a chronic intracortical BCI in monkeys to decode intended saccadic eye movement direction using activity from multiple frontal cortical areas. Main results. Intended saccade direction could be decoded in real time with high accuracy, particularly at contralateral locations. Accurate decoding was evident even at the beginning of the BCI session; no extensive BCI experience was necessary. High-frequency (80-500 Hz) local field potential magnitude provided the best performance, even over spiking activity, thus simplifying future BCI applications. Most of the information came from the frontal and supplementary eye fields, with relatively little contribution from dorsolateral prefrontal cortex. Significance. Our results support the feasibility of high-accuracy intracortical oculomotor BCIs that require little or no practice to operate and may be ideally suited for ‘point and click’ computer operation as used in most current AAC systems.

Pursuit gain and saccadic intrusions in first-degree relatives of probands with schizophrenia.

PubMed

Clementz, B A; Sweeney, J A; Hirt, M; Haas, G

1990-11-01

Oculomotor functioning of 26 probands with schizophrenia, 12 spectrum and 46 nonspectrum first-degree relatives, and 38 nonpsychiatric control subjects was evaluated. Spectrum relatives had more anticipatory saccades (ASs) and lower pursuit gain than nonspectrum relatives, who had more ASs and lower pursuit gain than control subjects. Probands also had lower pursuit gain than nonspectrum relatives and control subjects but did not differ from other groups on AS frequency. Control subjects had more globally accurate pursuit tracking (root mean square [RMS] error deviation) than both relative groups, whereas probands had the poorest RMS scores. Square wave jerk frequency did not differentiate the groups. Attention enhancement affected the frequency of ASs but did not affect either the other intrusive saccadic event or RMS scores. These results offer evidence that eye-movement dysfunction may serve as a biological marker for schizophrenia.

Visual working memory modulates low-level saccade target selection: Evidence from rapidly generated saccades in the global effect paradigm

PubMed Central

Hollingworth, Andrew; Matsukura, Michi; Luck, Steven J.

2013-01-01

In three experiments, we examined the influence of visual working memory (VWM) on the metrics of saccade landing position in a global effect paradigm. Participants executed a saccade to the more eccentric object in an object pair appearing on the horizontal midline, to the left or right of central fixation. While completing the saccade task, participants maintained a color in VWM for an unrelated memory task. Either the color of the saccade target matched the memory color (target match), the color of the distractor matched the memory color (distractor match), or the colors of neither object matched the memory color (no match). In the no-match condition, saccades tended to land at the midpoint between the two objects: the global, or averaging, effect. However, when one of the two objects matched VWM, the distribution of landing position shifted toward the matching object, both for target match and for distractor match. VWM modulation of landing position was observed even for the fastest quartile of saccades, with a mean latency as low as 112 ms. Effects of VWM on such rapidly generated saccades, with latencies in the express-saccade range, indicate that VWM interacts with the initial sweep of visual sensory processing, modulating perceptual input to oculomotor systems and thereby biasing oculomotor selection. As a result, differences in memory match produce effects on landing position similar to the effects generated by differences in physical salience. PMID:24190909

Attentional sensitivity and asymmetries of vertical saccade generation in monkey

NASA Technical Reports Server (NTRS)

Zhou, Wu; King, W. M.; Shelhamer, M. J. (Principal Investigator)

2002-01-01

The first goal of this study was to systematically document asymmetries in vertical saccade generation. We found that visually guided upward saccades have not only shorter latencies, but higher peak velocities, shorter durations and smaller errors. The second goal was to identify possible mechanisms underlying the asymmetry in vertical saccade latencies. Based on a recent model of saccade generation, three stages of saccade generation were investigated using specific behavioral paradigms: attention shift to a visual target (CUED paradigm), initiation of saccade generation (GAP paradigm) and release of the motor command to execute the saccade (DELAY paradigm). Our results suggest that initiation of a saccade (or "ocular disengagement") and its motor release contribute little to the asymmetry in vertical saccade latency. However, analysis of saccades made in the CUED paradigm indicated that it took less time to shift attention to a target in the upper visual field than to a target in the lower visual field. These data suggest that higher attentional sensitivity to targets in the upper visual field may contribute to shorter latencies of upward saccades.

Real-time estimation of horizontal gaze angle by saccade integration using in-ear electrooculography

PubMed Central

2018-01-01

The manuscript proposes and evaluates a real-time algorithm for estimating eye gaze angle based solely on single-channel electrooculography (EOG), which can be obtained directly from the ear canal using conductive ear moulds. In contrast to conventional high-pass filtering, we used an algorithm that calculates absolute eye gaze angle via statistical analysis of detected saccades. The estimated eye positions of the new algorithm were still noisy. However, the performance in terms of Pearson product-moment correlation coefficients was significantly better than the conventional approach in some instances. The results suggest that in-ear EOG signals captured with conductive ear moulds could serve as a basis for light-weight and portable horizontal eye gaze angle estimation suitable for a broad range of applications. For instance, for hearing aids to steer the directivity of microphones in the direction of the user’s eye gaze. PMID:29304120

The timing of sequences of saccades in visual search.

PubMed Central

Van Loon, E M; Hooge, I Th C; Van den Berg, A V

2002-01-01

According to the LATER model (linear approach to thresholds with ergodic rate), the latency of a single saccade in response to target appearance can be understood as a decision process, which is subject to (i) variations in the rate of (visual) information processing; and (ii) the threshold for the decision. We tested whether the LATER model can also be applied to the sequences of saccades in a multiple fixation search, during which latencies of second and subsequent saccades are typically shorter than that of the initial saccade. We found that the distributions of the reciprocal latencies for later saccades, unlike those of the first saccade, are highly asymmetrical, much like a gamma distribution. This suggests that the normal distribution of the rate r, which the LATER model assumes, is not appropriate to describe the rate distributions of subsequent saccades in a scanning sequence. By contrast, the gamma distribution is also appropriate to describe the distribution of reciprocal latencies for the first saccade. The change of the gamma distribution parameters as a function of the ordinal number of the saccade suggests a lowering of the threshold for second and later saccades, as well as a reduction in the number of target elements analysed. PMID:12184827

Eye movements during reading in aphasics.

PubMed

Klingelhöfer, J; Conrad, B

1984-01-01

In 40 normal subjects and in 21 patients with anomic, Wernicke's, and Broca's aphasia, eye movements were registered with DC-EOG during reading of two standardized texts and analysed with respect to the number of fixations and regressions and reading time. Patients with these aphasic syndromes developed different internal strategies of their saccadic construction: Patients with Wernicke's aphasia showed increasing difficulty in overcoming the text with a tendency to make smaller leaps over the line, with almost a complete disintegration of the saccadic structure ("strategy of small and smallest steps"). The saccadic pattern in Broca's aphasics was clearly better preserved. During oral reading there was a characteristic increase in fixation times and number of regressions ("motor waiting and searching behaviour"). Patients with anomic aphasia showed alterations most similar to the reading behaviour of unskilled normal readers.

Eye Gaze and Aging: Selective and Combined Effects of Working Memory and Inhibitory Control.

PubMed

Crawford, Trevor J; Smith, Eleanor S; Berry, Donna M

2017-01-01

Eye-tracking is increasingly studied as a cognitive and biological marker for the early signs of neuropsychological and psychiatric disorders. However, in order to make further progress, a more comprehensive understanding of the age-related effects on eye-tracking is essential. The antisaccade task requires participants to make saccadic eye movements away from a prepotent stimulus. Speculation on the cause of the observed age-related differences in the antisaccade task largely centers around two sources of cognitive dysfunction: inhibitory control (IC) and working memory (WM). The IC account views cognitive slowing and task errors as a direct result of the decline of inhibitory cognitive mechanisms. An alternative theory considers that a deterioration of WM is the cause of these age-related effects on behavior. The current study assessed IC and WM processes underpinning saccadic eye movements in young and older participants. This was achieved with three experimental conditions that systematically varied the extent to which WM and IC were taxed in the antisaccade task: a memory-guided task was used to explore the effect of increasing the WM load; a Go/No-Go task was used to explore the effect of increasing the inhibitory load; a 'standard' antisaccade task retained the standard WM and inhibitory loads. Saccadic eye movements were also examined in a control condition: the standard prosaccade task where the load of WM and IC were minimal or absent. Saccade latencies, error rates and the spatial accuracy of saccades of older participants were compared to the same measures in healthy young controls across the conditions. The results revealed that aging is associated with changes in both IC and WM. Increasing the inhibitory load was associated with increased reaction times in the older group, while the increased WM load and the inhibitory load contributed to an increase in the antisaccade errors. These results reveal that aging is associated with changes in both IC and

The engagement of cortical areas preceding exogenous vergence eye movements.

PubMed

Wojtczak-Kwaśniewska, Monika; Przekoracka-Krawczyk, Anna; Van der Lubbe, Rob H J

2018-01-01

Source analyses on event related potentials (ERPs) derived from the electroencephalogram (EEG) were performed to examine the respective roles of cortical areas preceding exogenously triggered saccades, combined convergences, and combined divergences. All eye movements were triggered by the offset of a central fixation light emitting diode (LED) and the onset of a lateral LED at various depths in an otherwise fully darkened room. Our analyses revealed that three source pairs, two located in the frontal lobe-the frontal eye fields (FEF) and an anterior frontal area-, and one located within the occipital cortex, can account for 99.2% of the observed ERPs. Overall, the comparison between source activities revealed the largest activity in the occipital cortex, while no difference in activity between FEF and the anterior frontal area was obtained. For all sources, increased activity was observed for combined vergences, especially combined convergences, relative to saccades. Behavioral results revealed that onset latencies were longest for combined convergences, intermediate for combined divergences, and the shortest for saccades. Together, these findings fit within a perspective in which both occipital and frontal areas play an important role in retinal disparity detection. In the case of saccades and combined divergences stimulus-locked activity was larger than response-locked activity, while no difference between stimulus- and response-locked activity was observed for combined convergences. These findings seem to imply that the electrophysiological activity preceding exogenous eye movements consists of a sensory-related part that is under cortical control, while subcortical structures may be held responsible for final execution.

Task-irrelevant own-race faces capture attention: eye-tracking evidence.

PubMed

Cao, Rong; Wang, Shuzhen; Rao, Congquan; Fu, Jia

2013-04-01

To investigate attentional capture by face's race, the current study recorded saccade latencies of eye movement measurements in an inhibition of return (IOR) task. Compared to Caucasian (other-race) faces, Chinese (own-race) faces elicited longer saccade latency. This phenomenon disappeared when faces were inverted. The results indicated that own-race faces capture attention automatically with high-level configural processing. © 2013 The Authors. Scandinavian Journal of Psychology © 2013 The Scandinavian Psychological Associations.

Extracting information of fixational eye movements through pupil tracking

NASA Astrophysics Data System (ADS)

Xiao, JiangWei; Qiu, Jian; Luo, Kaiqin; Peng, Li; Han, Peng

2018-01-01

Human eyes are never completely static even when they are fixing a stationary point. These irregular, small movements, which consist of micro-tremors, micro-saccades and drifts, can prevent the fading of the images that enter our eyes. The importance of researching the fixational eye movements has been experimentally demonstrated recently. However, the characteristics of fixational eye movements and their roles in visual process have not been explained clearly, because these signals can hardly be completely extracted by now. In this paper, we developed a new eye movement detection device with a high-speed camera. This device includes a beam splitter mirror, an infrared light source and a high-speed digital video camera with a frame rate of 200Hz. To avoid the influence of head shaking, we made the device wearable by fixing the camera on a safety helmet. Using this device, the experiments of pupil tracking were conducted. By localizing the pupil center and spectrum analysis, the envelope frequency spectrum of micro-saccades, micro-tremors and drifts are shown obviously. The experimental results show that the device is feasible and effective, so that the device can be applied in further characteristic analysis.

Oscillatory Alpha-Band Suppression Mechanisms during the Rapid Attentional Shifts Required to Perform an Anti-Saccade Task

PubMed Central

Belyusar, Daniel; Snyder, Adam C.; Frey, Hans-Peter; Harwood, Mark R.; Wallman, Josh; Foxe, John J.

2015-01-01

Neuroimaging has demonstrated anatomical overlap between covert and overt attention systems, although behavioral and electrophysiological studies have suggested that the two systems do not rely on entirely identical circuits or mechanisms. In a parallel line of research, topographically-specific modulations of alpha-band power (~8-14Hz) have been consistently correlated with anticipatory states during tasks requiring covert attention shifts. These tasks, however, typically employ cue-target-interval paradigms where attentional processes are examined across relatively protracted periods of time and not at the rapid timescales implicated during overt attention tasks. The anti-saccade task, where one must first covertly attend for a peripheral target, before executing a rapid overt attention shift (i.e. a saccade) to the opposite side of space, is particularly well-suited for examining the rapid dynamics of overt attentional deployments. Here, we asked whether alpha-band oscillatory mechanisms would also be associated with these very rapid overt shifts, potentially representing a common neural mechanism across overt and covert attention systems. High-density electroencephalography in conjunction with infra-red eye-tracking was recorded while participants engaged in both pro- and anti- saccade task blocks. Alpha power, time-locked to saccade onset, showed three distinct phases of significantly lateralized topographic shifts, all occurring within a period of less than one second, closely reflecting the temporal dynamics of anti-saccade performance. Only two such phases were observed during the pro-saccade task. These data point to substantially more rapid temporal dynamics of alpha-band suppressive mechanisms than previously established, and implicate oscillatory alpha-band activity as a common mechanism across both overt and covert attentional deployments. PMID:23041338

Asynchrony between position and motion signals in the saccadic system.

PubMed

Schreiber, Céline; Missal, Marcus; Lefèvre, Philippe

2006-02-01

The influence of position and motion signals on saccades was studied in two dimensions (2D) using a double step-ramp paradigm. We showed the presence of a predictive component in 2D catch-up saccade programming that is based on motion signals and influences both saccade amplitude and orientation. Interestingly, a significant proportion of catch-up saccades was characterized by a large curvature or a sudden change of direction in midflight for large values of retinal slip. For these saccades, a quantitative analysis showed that their trajectory could be explained by an asynchrony between position and motion signals in saccade programming. When the saccade trajectory was not straight, position error was always available first and influenced the initial orientation of the saccade, whereas retinal slip determined the final orientation. This new paradigm could be used in electrophysiological experiments, where it should prove to be very useful to study position and motion pathways separately in catch-up saccades.

Saccade selection when reward probability is dynamically manipulated using Markov chains

PubMed Central

Lovejoy, Lee P.; Krauzlis, Richard J.

2012-01-01

Markov chains (stochastic processes where probabilities are assigned based on the previous outcome) are commonly used to examine the transitions between behavioral states, such as those that occur during foraging or social interactions. However, relatively little is known about how well primates can incorporate knowledge about Markov chains into their behavior. Saccadic eye movements are an example of a simple behavior influenced by information about probability, and thus are good candidates for testing whether subjects can learn Markov chains. In addition, when investigating the influence of probability on saccade target selection, the use of Markov chains could provide an alternative method that avoids confounds present in other task designs. To investigate these possibilities, we evaluated human behavior on a task in which stimulus reward probabilities were assigned using a Markov chain. On each trial, the subject selected one of four identical stimuli by saccade; after selection, feedback indicated the rewarded stimulus. Each session consisted of 200–600 trials, and on some sessions, the reward magnitude varied. On sessions with a uniform reward, subjects (n = 6) learned to select stimuli at a frequency close to reward probability, which is similar to human behavior on matching or probability classification tasks. When informed that a Markov chain assigned reward probabilities, subjects (n = 3) learned to select the greatest reward probability more often, bringing them close to behavior that maximizes reward. On sessions where reward magnitude varied across stimuli, subjects (n = 6) demonstrated preferences for both greater reward probability and greater reward magnitude, resulting in a preference for greater expected value (the product of reward probability and magnitude). These results demonstrate that Markov chains can be used to dynamically assign probabilities that are rapidly exploited by human subjects during saccade target selection. PMID:18330552

Saccade selection when reward probability is dynamically manipulated using Markov chains.

PubMed

Nummela, Samuel U; Lovejoy, Lee P; Krauzlis, Richard J

2008-05-01

Markov chains (stochastic processes where probabilities are assigned based on the previous outcome) are commonly used to examine the transitions between behavioral states, such as those that occur during foraging or social interactions. However, relatively little is known about how well primates can incorporate knowledge about Markov chains into their behavior. Saccadic eye movements are an example of a simple behavior influenced by information about probability, and thus are good candidates for testing whether subjects can learn Markov chains. In addition, when investigating the influence of probability on saccade target selection, the use of Markov chains could provide an alternative method that avoids confounds present in other task designs. To investigate these possibilities, we evaluated human behavior on a task in which stimulus reward probabilities were assigned using a Markov chain. On each trial, the subject selected one of four identical stimuli by saccade; after selection, feedback indicated the rewarded stimulus. Each session consisted of 200-600 trials, and on some sessions, the reward magnitude varied. On sessions with a uniform reward, subjects (n = 6) learned to select stimuli at a frequency close to reward probability, which is similar to human behavior on matching or probability classification tasks. When informed that a Markov chain assigned reward probabilities, subjects (n = 3) learned to select the greatest reward probability more often, bringing them close to behavior that maximizes reward. On sessions where reward magnitude varied across stimuli, subjects (n = 6) demonstrated preferences for both greater reward probability and greater reward magnitude, resulting in a preference for greater expected value (the product of reward probability and magnitude). These results demonstrate that Markov chains can be used to dynamically assign probabilities that are rapidly exploited by human subjects during saccade target selection.

Experimental Test of Spatial Updating Models for Monkey Eye-Head Gaze Shifts

PubMed Central

Van Grootel, Tom J.; Van der Willigen, Robert F.; Van Opstal, A. John

2012-01-01

How the brain maintains an accurate and stable representation of visual target locations despite the occurrence of saccadic gaze shifts is a classical problem in oculomotor research. Here we test and dissociate the predictions of different conceptual models for head-unrestrained gaze-localization behavior of macaque monkeys. We adopted the double-step paradigm with rapid eye-head gaze shifts to measure localization accuracy in response to flashed visual stimuli in darkness. We presented the second target flash either before (static), or during (dynamic) the first gaze displacement. In the dynamic case the brief visual flash induced a small retinal streak of up to about 20 deg at an unpredictable moment and retinal location during the eye-head gaze shift, which provides serious challenges for the gaze-control system. However, for both stimulus conditions, monkeys localized the flashed targets with accurate gaze shifts, which rules out several models of visuomotor control. First, these findings exclude the possibility that gaze-shift programming relies on retinal inputs only. Instead, they support the notion that accurate eye-head motor feedback updates the gaze-saccade coordinates. Second, in dynamic trials the visuomotor system cannot rely on the coordinates of the planned first eye-head saccade either, which rules out remapping on the basis of a predictive corollary gaze-displacement signal. Finally, because gaze-related head movements were also goal-directed, requiring continuous access to eye-in-head position, we propose that our results best support a dynamic feedback scheme for spatial updating in which visuomotor control incorporates accurate signals about instantaneous eye- and head positions rather than relative eye- and head displacements. PMID:23118883

Impaired eye movements in presymptomatic spinocerebellar ataxia type 6.

PubMed

Christova, Peka; Anderson, John H; Gomez, Christopher M

2008-04-01

Early detection of impaired neurological function in neurodegenerative diseases may aid in understanding disease pathogenesis and timing of therapeutic trials. To identify early abnormalities of ocular motor function in individuals who have the spinocerebellar ataxia type 6 (SCA6) gene (CACNA1A) but no clinical symptoms. Physiological techniques were used to record and analyze eye movements and postural sway. Four presymptomatic and 5 ataxic patients with SCA6, genetically identified, and 10 healthy controls. Presymptomatic individuals had normal postural sway but definite ocular motor abnormalities. Two had a low-amplitude horizontal gaze-evoked nystagmus, 1 of whom had a significantly decreased eye velocity for upward saccades and an abnormal frequency of square-wave jerks. Another had abnormal square-wave jerks and a fourth had a reduced gain for pursuit tracking. Not all of the presymptomatic patients had the same findings, but a multivariate analysis discriminated the presymptomatic patients, as a group, from healthy controls and the ataxic patients. Among the earliest functional deficits in SCA6 are eye movement abnormalities, including impaired saccade velocity, saccade metrics, and pursuit gain. This suggests that early functional impairments are caused by cellular dysfunction and/or loss in the posterior cerebellar vermis and flocculus. These findings might help to determine the timing of a treatment and to define variables that could be used as outcome measures for the efficacy of therapeutic trials.

Macaque Pontine Omnipause Neurons Play No Direct Role in the Generation of Eye Blinks

PubMed Central

Schultz, K. P.; Williams, C. R.

2010-01-01

We recorded the activity of pontine omnipause neurons (OPNs) in two macaques during saccadic eye movements and blinks. As previously reported, we found that OPNs fire tonically during fixation and pause about 15 ms before a saccadic eye movement. In contrast, for blinks elicited by air puffs, the OPNs paused <2 ms before the onset of the blink. Thus the burst in the agonist orbicularis oculi motoneurons (OOMNs) and the pause in the antagonist levator palpabrae superioris motoneurons (LPSMNs) necessarily precede the OPN pause. For spontaneous blinks there was no correlation between blink and pause onsets. In addition, the OPN pause continued for 40–60 ms after the time of the maximum downward closing of the eyelids, which occurs around the end of the OOMN burst of firing. LPSMN activity is not responsible for terminating the OPN pause because OPN resumption was very rapid, whereas the resumption of LPSMN firing during the reopening phase is gradual. OPN pause onset does not directly control blink onset, nor does pause offset control or encode the transition between the end of the OOMN firing and the resumption of the LPSMNs. The onset of the blink-related eye transients preceded both blink and OPN pause onsets. Therefore they initiated while the saccadic short-lead burst neurons were still fully inhibited by the OPNs and cannot be saccadic in origin. The abrupt dynamic change of the vertical eye transients from an oscillatory behavior to a single time constant exponential drift predicted the resumption of the OPNs. PMID:20164389

How memory mechanisms are a key component in the guidance of our eye movements: evidence from the global effect.

PubMed

Silvis, J D; Van der Stigchel, S

2014-04-01

Investigating eye movements has been a promising approach to uncover the role of visual working memory in early attentional processes. Prior research has already demonstrated that eye movements in search tasks are more easily drawn toward stimuli that show similarities to working memory content, as compared with neutral stimuli. Previous saccade tasks, however, have always required a selection process, thereby automatically recruiting working memory. The present study was an attempt to confirm the role of working memory in oculomotor selection in an unbiased saccade task that rendered memory mechanisms irrelevant. Participants executed a saccade in a display with two elements, without any instruction to aim for one particular element. The results show that when two objects appear simultaneously, a working memory match attracts the first saccade more profoundly than do mismatch objects, an effect that was present throughout the saccade latency distribution. These findings demonstrate that memory plays a fundamental biasing role in the earliest competitive processes in the selection of visual objects, even when working memory is not recruited during selection.

Modeling eye-head gaze shifts in multiple contexts without motor planning

PubMed Central

Haji-Abolhassani, Iman; Guitton, Daniel

2016-01-01

During gaze shifts, the eyes and head collaborate to rapidly capture a target (saccade) and fixate it. Accordingly, models of gaze shift control should embed both saccadic and fixation modes and a mechanism for switching between them. We demonstrate a model in which the eye and head platforms are driven by a shared gaze error signal. To limit the number of free parameters, we implement a model reduction approach in which steady-state cerebellar effects at each of their projection sites are lumped with the parameter of that site. The model topology is consistent with anatomy and neurophysiology, and can replicate eye-head responses observed in multiple experimental contexts: 1) observed gaze characteristics across species and subjects can emerge from this structure with minor parametric changes; 2) gaze can move to a goal while in the fixation mode; 3) ocular compensation for head perturbations during saccades could rely on vestibular-only cells in the vestibular nuclei with postulated projections to burst neurons; 4) two nonlinearities suffice, i.e., the experimentally-determined mapping of tectoreticular cells onto brain stem targets and the increased recruitment of the head for larger target eccentricities; 5) the effects of initial conditions on eye/head trajectories are due to neural circuit dynamics, not planning; and 6) “compensatory” ocular slow phases exist even after semicircular canal plugging, because of interconnections linking eye-head circuits. Our model structure also simulates classical vestibulo-ocular reflex and pursuit nystagmus, and provides novel neural circuit and behavioral predictions, notably that both eye-head coordination and segmental limb coordination are possible without trajectory planning. PMID:27440248

Eye movements when viewing advertisements

PubMed Central

Higgins, Emily; Leinenger, Mallorie; Rayner, Keith

2013-01-01

In this selective review, we examine key findings on eye movements when viewing advertisements. We begin with a brief, general introduction to the properties and neural underpinnings of saccadic eye movements. Next, we provide an overview of eye movement behavior during reading, scene perception, and visual search, since each of these activities is, at various times, involved in viewing ads. We then review the literature on eye movements when viewing print ads and warning labels (of the kind that appear on alcohol and tobacco ads), before turning to a consideration of advertisements in dynamic media (television and the Internet). Finally, we propose topics and methodological approaches that may prove to be useful in future research. PMID:24672500

Graded versus ungraded inferior oblique anterior transposition in patients with asymmetric dissociated vertical deviation.

PubMed

Rajavi, Zhale; Feizi, Mohadeseh; Naderi, Ali; Sabbaghi, Hamideh; Behradfar, Narges; Yaseri, Mehdi; Faghihi, Mohammad

2017-12-01

To report the surgical outcomes of graded versus ungraded inferior oblique anterior transposition (IOAT) in treatment of patients with asymmetric dissociated vertical deviation (DVD) and bilateral inferior oblique overaction (IOOA). A total of 74 eyes of 37 patients with asymmetric DVD (interocular difference of ≥5 Δ ) and bilateral IOOA of > +1 were included in this randomized clinical trial. In the ungraded group (n = 18), both inferior oblique muscles were sutured at the inferior rectus level; in the graded group (n = 19), the inferior oblique muscles of eyes with more DVD were sutured at the level of the inferior rectus and inferior oblique muscles of eyes with less DVD were sutured 2 mm posterior to the level of the inferior rectus muscle. DVD was significantly reduced in each group (P < 0.001 for both). Although the postoperative mean difference of asymmetry of DVD was less in the ungraded group compared to the graded group (1.2 ± 1.9 vs 3.2 ± 1.2 [P = 0.001]), the absolute amounts of reduction of DVD asymmetry were similar (4.3 ± 2.3 vs 4.4 ± 3.1 [P = 0.78]). IOOA and V patterns were also reduced postoperatively. Each method of IOAT was effective in reducing DVD, asymmetry, IOOA, and V patterns. Copyright © 2017 American Association for Pediatric Ophthalmology and Strabismus. Published by Elsevier Inc. All rights reserved.