RESPONSES OF TONICALLY DISCHARGING NEURONS IN MONKEY STRIATUM TO VISUAL-STIMULI PRESENTED UNDER PASSIVE CONDITIONS AND DURING TASK-PERFORMANCE

To test whether the responsiveness of tonically discharging neurons fr om monkey striatum is dependent on the motor or rewarding features of the conditioned stimuli, we studied the responses of these neurons to visual stimuli presented under two behavioral conditions: during an op erant task in which the stimulus triggered a movement to obtain a rewa rd, and in a non-performing state in which the stimulus was consistent ly followed by a reward outside of a task. Most of the neurons tested (110/158) responded to the stimuli presented in both conditions, while a relatively small number of neurons (35/158) showed selective respon ses in one or other of the conditions. A gradual disappearance of neur onal responses occurred in the passive state when presenting a stimulu s which was never followed by reward. These results provide evidence t hat tonic striatal neurons may be involved in detecting stimuli predic ting reward, regardless of the behavioral contingency of those stimuli .