[Abstract Title]. - Society for Neuroscience

standard visuomotor transformations, the visual information used to perform a motor task does
not come from the object one‟s hand is interacting with. A common example is a reach for a
peripherally-viewed computer mouse sitting on a flat tabletop while viewing an icon on a
computer monitor, and then sliding the mouse forward on a horizontal plane in order to displace
a cursor vertically to touch the icon. In this situation, the direction of gaze and the manipulated
object (the cursor) are in different depths or spatial planes. Our previous work has begun to
characterize the contributions of different brain pathways to the processing of different levels of
visuomotor compatibility. In this study we test the hypothesis that neural pathways involving the
superior parietal lobule are involved in basic visuomotor transformations and in decoupling the
movements of the eyes and the hand, a skill required for some non-standard mapping tasks. We
examined the performance of a bilateral optic ataxic patient in reaching tasks which involved
different levels of dissociation (spatial plane changes, rotated visual feedback, arbitrary
associations). We observed a gaze-direction dependent reaching bias when the visual feedback of
hand location was rotated. Importantly, we found that these misreaches did not change when the
hand was also moving in a different spatial plane. That is, this patient, who is missing most of
both superior parietal lobules, is successful in transforming the reach target into a different plane
in space. However, she is unable to decouple the eye and the hand fully in this new motion plane.
These data suggest that the different levels of dissociation examined here are processed by
independent neural pathways.
Disclosures: J.A. Granek , None; L.E. Sergio, None; L. Pisella, None; A. Blangero, None; Y.
Rossetti, None.
Poster
262. Visually-Guided Reaching II
Time: Sunday, November 16, 2008, 1:00 pm - 5:00 pm
Program#/Poster#: 262.18/CC32
Topic: D.05.d. Visually guided reaching
Support: Heart and Stroke Foundation Centre for Stroke Recovery
Title: Post-stroke patients with substantial right parietal cortex injury demonstrate an ability to
perform successful visuospatial transformations
Authors: *W. J. TIPPETT, S. E. BLACK;
Cogntive Neurol., Sunnybrook Hlth. Sci. Cen, Toronto, ON, Canada
Abstract: Introduction: The ability to perform successful visuospatial/visuomotor
transformations relies on effective processing primarily within the right posterior parietal cortex