DECIDING NOT TO GO - NEURONAL CORRELATES OF RESPONSE SELECTION IN A GO NOGO TASK IN PRIMATE PREMOTOR AND PARIETAL CORTEX/

Monkeys performed reaching movements in two opposite directions in a s ymmetrically rewarded GO/NOGO task with an instructed-delay period. In structional cues were presented at the target locations. The decision not to move was clearly reflected in cell activity in dorsal premotor cortex, but not in parietal cortex area 5. In promotor cortex, the ini tial response (<250 msec) of most cells to the appearance of the instr uctional cues in GO and NOGO trials was similar. However, by the end o f the delay period, the responses of most cells were statistically dif ferent between the two trial types, and the population signals were mu ch less directional in the NOGG trials than in the GO trials. In area 5, in contrast, single-cell and population signals were generally simi lar and strongly directional in both GO and NOGG trials. This result s uggests a role for area 5 in visuomotor analysis for the guidance of l imb movements. It further suggests that separate representations of po tential motor responses to external inputs and of the intended respons e to that input can coexist in parietal and premotor cortex, respectiv ely.