scholarly journals Control of Reflexive Saccades following Hemispherectomy

2011 ◽  
Vol 23 (6) ◽  
pp. 1368-1378 ◽  
Author(s):  
Patricia A. Reuter-Lorenz ◽  
Troy M. Herter ◽  
Daniel Guitton
Keyword(s):  
Superior Colliculus ◽  
Inhibitory Control ◽  
Intractable Epilepsy ◽  
Short Latency ◽  
Gap Effect ◽  
Express Saccades ◽  
Antisaccade Task ◽  
Intact Side ◽  
Reflexive Saccades ◽  
Saccade Generation

Individuals who have undergone hemispherectomy for treatment of intractable epilepsy offer a rare and valuable opportunity to examine the ability of a single cortical hemisphere to control oculomotor performance. We used peripheral auditory events to trigger saccades, thereby circumventing dense postsurgical hemianopia. In an antisaccade task, patients generated numerous unintended short-latency saccades toward contralesional auditory events, indicating pronounced limitations in the ability of a single hemicortex to exert normal inhibitory control over ipsilateral (i.e., contralesional) reflexive saccade generation. Despite reflexive errors, patients retained an ability to generate correct antisaccades in both directions. The prosaccade task revealed numerous contralesional express saccades, a robust contralesional gap effect, but the absence of both effects for ipsilesional saccades. These results indicate limits to the saccadic control capabilities following hemispherectomy: A single hemicortex can mediate antisaccades in both directions, but plasticity does not extend fully to the bilateral inhibition of reflexive saccades. We posit that these effects are due to altered control dynamics that reduce the responsivity of the superior colliculus on the intact side and facilitate the release of an auditory-evoked ocular grasp reflex into the blind hemifield that the intact hemicortex has difficulty suppressing.

The effect of frontal eye field and superior colliculus lesions on saccadic latencies in the rhesus monkey

1987 ◽  
Vol 57 (4) ◽  
pp. 1033-1049 ◽  
Author(s):  
P. H. Schiller ◽  
J. H. Sandell ◽  
J. H. Maunsell
Keyword(s):  
Eye Movements ◽  
Superior Colliculus ◽  
Short Latency ◽  
The Other ◽  
Frontal Eye Field ◽  
Express Saccades ◽  
Unimodal Distribution ◽  
Other Hand ◽  
Eye Field ◽  
The Mean

Rhesus monkeys were trained to make saccadic eye movements to visual targets using detection and discrimination paradigms in which they were required to make a saccade either to a solitary stimulus (detection) or to that same stimulus when it appeared simultaneously with several other stimuli (discrimination). The detection paradigm yielded a bimodal distribution of saccadic latencies with the faster mode peaking around 100 ms (express saccades); the introduction of a pause between the termination of the fixation spot and the onset of the target (gap) increased the frequency of express saccades. The discrimination paradigm, on the other hand, yielded only a unimodal distribution of latencies even when a gap was introduced, and there was no evidence for short-latency "express" saccades. In three monkeys either the frontal eye field or the superior colliculus was ablated unilaterally. Frontal eye field ablation had no discernible long-term effects on the distribution of saccadic latencies in either the detection or discrimination tasks. After unilateral collicular ablation, on the other hand, express saccades obtained in the detection paradigm were eliminated for eye movements contralateral to the lesion, leaving only a unimodal distribution of latencies. This deficit persisted throughout testing, which in one monkey continued for 9 mo. Express saccades were not observed again for saccades contralateral to the lesion, and the mean latency of the contralateral saccades was longer than the mean latency of the second peak for the ipsiversive saccades. The latency distribution of saccades ipsiversive to the collicular lesion was unaffected except for a few days after surgery, during which time an increase in the proportion of express saccades was evident. Saccades obtained with the discrimination paradigm yielded a small but reliable increase in saccadic latencies following collicular lesions, without altering the shape of the distribution. Unilateral muscimol injections into the superior colliculus produced results similar to those obtained immediately after collicular lesions: saccades contralateral to the injection site were strongly inhibited and showed increased saccadic latencies. This was accompanied by a decrease of ipsilateral saccadic latencies and an increase in the number of saccades falling into the express range. The results suggest that the superior colliculus is essential for the generation of short-latency (express) saccades and that the frontal eye fields do not play a significant role in shaping the distribution of saccadic latencies in the paradigms used in this study.(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals The role of the superior colliculus in saccade initiation: a study of express saccades and the gap effect

2000 ◽  
Vol 40 (20) ◽  
pp. 2763-2777 ◽  
Author(s):  
David Sparks ◽  
W.H. Rohrer ◽  
Yihong Zhang
Keyword(s):  
Superior Colliculus ◽  
Gap Effect ◽  
Express Saccades

Two attentional components for two purposes

1997 ◽  
Vol 20 (4) ◽  
pp. 770-771
Author(s):  
B. Fischer ◽  
H. Weber
Keyword(s):  
Error Rate ◽  
Express Saccades ◽  
Antisaccade Task ◽  
Voluntary Attention ◽  
Peripheral Location ◽  
Fixation System ◽  
Saccade Generation

Inappropriate saccades are prevented by fixation and by voluntary attention. The fixation system inhibits the saccade system. Like monkeys without a fixation system, humans with a weak fixation system produce many express saccades and cannot suppress prosaccades in an antisaccade task. With permanent attention to a peripheral location only a few express saccades to a stimulus at this location can be elicited: the sustained component of attention acts like fixation. When attention is captured by a precue, more express saccades are obtained: the stimulus-driven component of attention facilitates saccade generation. If the cue correctly indicates the direction for an antisaccade error rate and latencies are increased.

The underrated role of the “move system” in determining saccade latency

1999 ◽  
Vol 22 (4) ◽  
pp. 681-682 ◽  
Author(s):  
Michael C. Dorris ◽  
Douglas P. Munoz
Keyword(s):  
Superior Colliculus ◽  
Target Location ◽  
Saccade Latency ◽  
Gap Effect ◽  
Target Specificity ◽  
Express Saccades ◽  
Latency Reduction ◽  
Extensive Training ◽  
Target Article

The Findlay & Walker target article emphasizes the role of the target-nonspecific “fixate” system while downplaying the role of the target-specific “move” system in determining saccade latency. We agree that disengagement of the fixate system is responsible for the target-nonspecific latency reduction associated with the gap effect. However, high target predictability and extensive training at a target location can also result in latency reductions, the culmination of this being express saccades. The target-specificity associated with the latter forms of latency reduction implicate a mechanism involving the move system. Recently discovered neurophysiological correlates underlying these behavioural phenomena reside in the superior colliculus.

scholarly journals Impairment but not abolishment of express saccades after unilateral or bilateral inactivation of the frontal eye fields

2020 ◽  
Vol 123 (5) ◽  
pp. 1907-1919 ◽  
Author(s):  
Suryadeep Dash ◽  
Tyler R. Peel ◽  
Stephen G. Lomber ◽  
Brian D. Corneil
Keyword(s):  
Superior Colliculus ◽  
Peak Velocity ◽  
Critical Role ◽  
Frontal Eye Fields ◽  
Express Saccades ◽  
Express Saccade ◽  
Cortical Cooling ◽  
Saccade Generation

Express saccades are the shortest-latency saccade. The frontal eye fields (FEF) are thought to promote express saccades by presetting the superior colliculus. Here, by reversibly inactivating the FEF either unilaterally or bilaterally via cortical cooling, we support this by showing that the FEF plays a facilitative but not critical role in express saccade generation. We also found that FEF inactivation lowered express saccade peak velocity, emphasizing a contribution of the FEF to express saccade kinematics.

An examination of the variables that affect express saccade generation

2004 ◽  
Vol 21 (2) ◽  
pp. 119-127 ◽  
Author(s):  
PETER H. SCHILLER ◽  
JOHANNES HAUSHOFER ◽  
GEOFFERY KENDALL
Keyword(s):  
Rhesus Monkeys ◽  
Target Onset ◽  
Express Saccades ◽  
Express Saccade ◽  
Saccadic System ◽  
Fixation Spot ◽  
Temporal Asynchrony ◽  
Saccade Generation ◽  
Gap Time

The frequency with which express saccades are generated under a variety of conditions in rhesus monkeys was examined. Increasing the gap time between fixation spot termination and target onset increased express saccade frequency but was progressively less effective in doing so as the number of target positions in the sample was increased. Express saccades were rarely produced when two targets were presented simultaneously and the choice of either of which was rewarded; a temporal asynchrony of only 17 ms between the targets reinstated express saccade generation. Express saccades continued to be generated when the vergence or pursuit systems was coactivated with the saccadic system.

Disturbances in the Control of Saccadic Eye Movement and Eye-Head Coordination in Schizophrenics1

1991 ◽  
Vol 1 (2) ◽  
pp. 171-180
Author(s):  
Junko Fukushima ◽  
Kikuro Fukushima ◽  
Nobuyuki Morita ◽  
Itaru Yamashita
Keyword(s):  
Frontal Cortex ◽  
Head Movement ◽  
Head Movements ◽  
Saccadic Eye Movement ◽  
Antisaccade Task ◽  
Schizophrenic Patients ◽  
Saccade Task ◽  
Cortical Dysfunction ◽  
Reflexive Saccades ◽  
Target Memory

Some schizophrenic patients have been known to have frontal cortical dysfunction. In view of the evidence that voluntary purposive eye movements and rapid head movements involve areas of the frontal cortex, investigations of saccade performance have been carried out on schizophrenics in various laboratories. We have compared performance of schizophrenic patients in tasks involving inhibition of reflexive saccades (no-saccade) and initiation of saccades without target (memory-saccade) with performance in. the antisaccade task. These measures were also compared with results of eye-head coordination tasks. Schizophrenics showed more errors and significantly longer latencies, with lower peak velocities at large amplitudes, in both the anti saccade task and the memory-saccade task. Performance with coordinated eye-head movement was basically similar, except for significantly longer latencies of head movement. These results suggest that schizophrenics may have a disturbance in initiating and executing purposive saccades without targets, and that dysfunction of the frontal cortex may contribute to this disturbance.

scholarly journals The Disengagement of Visual Attention: An Eye-Tracking Study of Cognitive Impairment, Ethnicity and Age

2020 ◽  
Vol 10 (7) ◽  
pp. 461
Author(s):  
Megan Polden ◽  
Thomas D. W. Wilcockson ◽  
Trevor J. Crawford
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Cognitive Impairment ◽  
Inhibitory Control ◽  
Reaction Times ◽  
Gap Effect ◽  
Cognitively Impaired ◽  
The Mean ◽  
Disengagement Of Attention ◽  
Effect Of Age

Various studies have shown that Alzheimer’s disease (AD) is associated with an impairment of inhibitory control, although we do not have a comprehensive understanding of the associated cognitive processes. The ability to engage and disengage attention is a crucial cognitive operation of inhibitory control and can be readily investigated using the “gap effect” in a saccadic eye movement paradigm. In previous work, various demographic factors were confounded; therefore, here, we examine separately the effects of cognitive impairment in Alzheimer’s disease, ethnicity/culture and age. This study included young (N = 44) and old (N = 96) European participants, AD (N = 32), mildly cognitively impaired participants (MCI: N = 47) and South Asian older adults (N = 94). A clear reduction in the mean reaction times was detected in all the participant groups in the gap condition compared to the overlap condition, confirming the effect. Importantly, this effect was also preserved in participants with MCI and AD. A strong effect of age was also evident, revealing a slowing in the disengagement of attention during the natural process of ageing.

scholarly journals Working Memory and the Suppression of Reflexive Saccades

2002 ◽  
Vol 14 (1) ◽  
pp. 95-103 ◽  
Author(s):  
Jason P. Mitchell ◽  
C. Neil Macrae ◽  
Iain D. Gilchrist
Keyword(s):  
Working Memory ◽  
Memory Load ◽  
Critical Role ◽  
Memory Task ◽  
Behavioral Responses ◽  
Error Rates ◽  
Antisaccade Task ◽  
Working Memory Load ◽  
Reflexive Saccades ◽  
Back Task

Conscious behavioral intentions can frequently fail under conditions of attentional depletion. In attempting to trace the cognitive origin of this effect, we hypothesized that failures of action control—specifically, oculomotor movement—can result from the imposition of fronto-executive load. To evaluate this prediction, participants performed an antisaccade task while simultaneously completing a working-memory task that is known to make variable demands on prefrontal processes (n-back task, see Jonides et al., 1997). The results of two experiments are reported. As expected, antisaccade error rates were increased in accordance with the fronto-executive demands of the n-back task (Experiment 1). In addition, the debilitating effects of working-memory load were restricted to the inhibitory component of the antisaccade task (Experiment 2). These findings corroborate the view that working memory operations play a critical role in the suppression of prepotent behavioral responses.

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