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Tuesday April 7th, 2009 from 9:30 to 11:30
Location: Auditoire Maisin, UCL Brussels
by Michael E. Goldberg, - David Mahoney Professor of Brain & Behavior, Neuroscience, Neurology, Psychiatry, Ophthalmology;
- Director, Mohoney Center;
- Department of Neuroscience, Columbia Univ., New York, USA.
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Abstract: The lateral intraparietal area serves as a priority map of the visual
field in gaze-centered coordinates. This map, however, does not depend
upon actual visual stimuli. It has a strong memory input, even for
objects which did not appear on the current trial. The map is
spatially accurate - it compensates for stimuli which appear before an
intervening saccade. Part of this compensation occurs by virtue of an
expansion of receptive field along the trajectory of the saccade. A
later receptive field shift, seen only as the shift of a memory trace,
occurs later and is not associate with a receptive field expansion.
The question of the coordinate system of the map is quite complicated -
we use saccadic adaptation to dissociate the retinal location of a
visual stimulus from the amplitude of the saccade which the stimulus
evokes. The priority map is in visual coordinates, even for
presaccadic activity. However, the vector which shifts the saccade
starts out in visual coordinates and ends up in veridical motor or eye
position coordinates. Thus there may be two independent mechanisms of
receptive field shift: an early one in visual coordinates and a later
one in veridical coordinates. Because this later shift is so slow it
could arise not from corollary discharge or efference copy, but from
oculomotor proprioception.
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last update: March 12th, 2009
Author: Philippe LEFEVRE
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