Document Detail


Saccades to the seeing visual hemifield in hemidecorticate patients exhibit task-dependent reaction times and hypometria.
MedLine Citation:
PMID:  17516057     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
In three patients who had one cortical hemisphere removed surgically (hemidecortication), we studied visually-triggered saccades directed contralateral to the intact cortical hemisphere (i.e., ipsilesional saccades). Both saccade reaction times (SRTs) and accuracy of these saccades have been reported as abnormal in hemidecorticate patients, but not monkeys. One explanation for this difference is that deficits in hemidecorticate patients may not have been directly caused by removal of cortical oculomotor structures themselves, but may have been a manifestation of compensatory strategies used to cope with contralesional hemianopia. We hypothesized that deficits in saccade performance to the ipsilesional (seeing) visual hemifield would be directly linked to how easily patients could localize targets in their blind hemifield with searching saccades. To test this hypothesis, we examined how deficits in our patients varied when targets were: (1) randomly presented to either the seeing or blind hemifield for long durations thereby permitting searching saccades in the blind hemifield; (2) presented as in Experiment 1, but briefly flashed thereby removing visual feedback prior to saccade onset thereby rendering searching saccades useless; (3) briefly flashed as in Experiment 2, but at random locations in only the seeing hemifield (blind hemifield irrelevant). Mean SRTs to the seeing hemifield were 165 ms longer than normal in Experiment 2, but only about 40 ms longer in Experiments 1 and 3. Saccade accuracy was characterized by task-dependent hypometria in all three experiments with a mean undershoot of about twice the amplitude variance. The largest undershoots were in Experiments 2 and 3. Our data suggest that deficits resulted from the direct effects of the lesions themselves coupled with context-dependent strategies used to cope with contralesional hemianopia.
Authors:
Troy M Herter; Daniel Guitton
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2007-05-22
Journal Detail:
Title:  Experimental brain research     Volume:  182     ISSN:  0014-4819     ISO Abbreviation:  Exp Brain Res     Publication Date:  2007 Sep 
Date Detail:
Created Date:  2007-08-27     Completed Date:  2008-02-07     Revised Date:  2013-12-13    
Medline Journal Info:
Nlm Unique ID:  0043312     Medline TA:  Exp Brain Res     Country:  Germany    
Other Details:
Languages:  eng     Pagination:  11-25     Citation Subset:  IM    
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MeSH Terms
Descriptor/Qualifier:
Adolescent
Adult
Auditory Perception / physiology
Blindness / physiopathology
Data Interpretation, Statistical
Decerebrate State / pathology,  physiopathology*
Electrooculography
Epilepsy / surgery
Female
Functional Laterality / physiology*
Humans
Intelligence Tests
Magnetic Resonance Imaging
Male
Neurosurgical Procedures
Photic Stimulation
Psychomotor Performance / physiology*
Reaction Time / physiology*
Saccades / physiology*
Visual Acuity
Visual Fields / physiology*
Visual Perception / physiology

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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