Single unit activity in basal ganglia of monkeys during performance of a delayed response task.

Single unit activity was recorded from the basal ganglia (caudate, putamen and globus pallidus) of monkeys during the performance of a delayed-response task. The task was divided into five epochs: stimulus onset, delay, pre-response, post-response and reqard. A high percentage of units recorded from the basal ganglia were found to show significant changes in activity during one or more epochs. Examination of the proportion of units excited or inhibited during a particular epoch indicated that brief increases or decreases in unit firing rates occurred "in phase" in both pallidum and caudate. Longer lasting firing rate changes, however, tended to occur in opposite directions in these two structures. This latter finding is interpreted as representing the consequence of persistent increases or decreases in activity of inhibitory interneurons in the caudate nucleus.