G.Stoet*; L.H.Snyder

We studied neural correlates of task information and task-specific stimulus processing in two macaque monkeys. Two discrimination tasks were randomly interleaved. Depending on the task, animals judged either stimulus color (red or green) or orientation (horizontal or vertical). Trials started with a 250 ms visual task instruction. After a 450 ms preparation interval, a colored, oriented target appeared. Animals pressed one of two buttons to indicate their judgment. We defined a task-specific information processing cell as one that encodes task information, in which the task encoding persists after the target appears, and in which the neural responses to identical targets depend on the task being performed and the cell's task preference. To determine whether cells in PPC encode task information, we compared activity during the last 250 ms of the preparation interval following different task instructions (376 neurons). In the lateral bank of the IPS (IPS-L), the firing of 17% of neurons depended on which task was instructed, regardless of the instruction format (P<.01). Across this population of IPS-L task-selective cells, task effects persisted even after the target was presented (150-350 ms after target presentation, paired t-test, P<0.05). Finally, the response to identical targets was larger during performance of the preferred task compared to the non-preferred task (150-350 ms after target presentation, paired t-test, P<0.01). Effects were similar in both animals. These data indicate that IPS-L cells encode task information, and suggest that task-encoding cells are involved in the task-specific processing of visual information.

Citation: G.Stoet, L.H.Snyder. TASK - SPECIFIC PROCESSING OF STIMULI IN MONKEY POSTERIOR PARIETAL CORTEX ( PPC ) Program No. 559.13. 2002 Abstract Viewer/Itinerary Planner. Washington, DC: Society for Neuroscience, 2002. CD-ROM.