Modulation of neural activity in human visual cortex during saccade programming

Item type:	Thesis of the University of Regensburg (PhD)
Date:	March 2007
Referee:	Prof. Dr. Mark W. Greenlee
Date of exam:	7 February 2007
Additional Information (public):	http://www.jneurosci.org/cgi/reprint/26/22/5965
Institutions:	Human Sciences > Institut für Psychologie > Lehrstuhl für Psychologie I (Allgemeine Psychologie I und Methodenlehre) - Prof. Dr. Mark W. Greenlee
Keywords:	Sehrinde , Großhirnrinde , NMR-Tomographie , Vision , Aktives Sehen , Sakkade , , Saccaddic suppression , eye movements , functional magnetic resonance imaging , primary visual cortex
Dewey Decimal Classification:	100 Philosophy & psychology > 150 Psychology
Status:	Published
Refereed:	Yes, this version has been refereed
Created at the University of Regensburg:	Yes
Item ID:	10531

Abstract (English)

Saccadic eye movements are responsible for bringing relevant parts of the visual field onto the fovea for detailed analysis. Since the retina is physiologically unable to deliver sharp images at very high transsaccadic speeds, the visual system minimizes the repercussion of the blurry images we would otherwise perceive during transsaccadic vision by reducing general visual sensitivity and ...

Abstract (English)

Saccadic eye movements are responsible for bringing relevant parts of the visual field onto the fovea for detailed analysis. Since the retina is physiologically unable to deliver sharp images at very high transsaccadic speeds, the visual system minimizes the repercussion of the blurry images we would otherwise perceive during transsaccadic vision by reducing general visual sensitivity and increasing the detection threshold for visual stimuli. Ruling out a pure retinal origin, the effects of saccadic suppression can already be observed some 75 ms before the onset of a saccadic eye movement and are maximal at the onset of motion. The perception of a briefly presented stimulus immediately before the onset of any retinal motion is thus impaired despite the fact that this stimulus is projected onto the stationary retina and is, therefore, physically identical to that presented when no saccadic programming is in course. In this fMRI event-related study, we flashed Gabor patches at different times before the onset of a horizontal saccade and measured BOLD responses at their encoding regions in primary visual cortex (V1) while subjects judged the relative orientation of the stimuli. Closely matching the significant reduction in behavioral performance, the amplitude of the responses in V1 consistently decreased as the stimuli were presented closer to the saccadic onset. These results demonstrate that the neural processes underlying saccade programming transiently modulate cortical responses to briefly presented visual stimuli in areas as early as V1, providing further evidence for the existence of an active saccadic suppression mechanism in humans.

Translation of the abstract (German)

Bereits 75 ms vor Beginn einer sakkadischen Augenbewegung reduziert sich die visuelle Sensitivität deutlich, obwohl die Stimuli zur dieser Zeit auf eine stabile Retina projiziert werden (sakkadische Suppression). In einer event-related fMRI-Studie wird die BOLD-Antwort auf vier periphere Gabor-Reize untersucht. Die Reize wurden kurz vor Beginn einer Sakkade für 8 ms präsentiert. Die BOLD-Antwort ...

Translation of the abstract (German)

Bereits 75 ms vor Beginn einer sakkadischen Augenbewegung reduziert sich die visuelle Sensitivität deutlich, obwohl die Stimuli zur dieser Zeit auf eine stabile Retina projiziert werden (sakkadische Suppression). In einer event-related fMRI-Studie wird die BOLD-Antwort auf vier periphere Gabor-Reize untersucht. Die Reize wurden kurz vor Beginn einer Sakkade für 8 ms präsentiert. Die BOLD-Antwort war hierbei parametrisch abhängig von SOA, je kürzer das Intervall zwischen Gabor-Reiz und Sakkadenbeginn, desto geringer die Amplitude des BOLD-Signals. Die Ergebnisse weisen darauf hin, dass sakkadische Suppression bereits auf subkortikaler Ebene wirksam wird, noch bevor die visuellen Informationen den Kortex erreichen.

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Translation of the abstract (German)

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