Abstract

Here we investigate outstanding issues regarding cortical support of spatial working memory with the use of event-related fMRI at 4T. We used analytic methods that selectively identify delay-period activity during oculomotor delayed response tasks with the goal of addressing two questions. First, does the degree of delay-period activity in the frontal and parietal cortex predict subsequent memory-guided saccade accuracy? We address this question by relating saccade accuracy (via simultaneous monitoring of eye-position) with earlier delay-period MR signal changes. Second, does the delay-period activity most likely reflect maintenance of a spatial location (retrospective spatial code) or maintenance of an oculomotor program (prospective motor code)? We address this question by comparing delay-period activity between trials when a saccade was made to the remembered target location with trials when a saccade was made to a target that did not match the remembered location. In the latter condition, subjects could not prepare a saccade during the delay because the saccade goal was unknown until after the delay. Analyses indicate that delay-period activity localizes to common dorsal frontal and parietal areas and that differential activity is found depending on whether the subject has knowledge of the direction of the forthcoming saccade. Preliminary analyses also indicate that the fidelity of the spatial representation is encoded in the degree of delay-period activity in these regions.

From: Curtis, C. E. and M. D'Esposito (2002). Maintenance of spatial information in the frontal and parietal cortex during oculmotor delayed-response tasks. Society for Neuroscience, Orlando.