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 from 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 operant task in which the stimulus triggered a movement to obtain a reward, and in a non-performing state in which the stimulus was consistently 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 responses in one or other of the conditions. A gradual disappearance of neuronal responses occurred in the passive state when presenting a stimulus which was never followed by reward. These results provide evidence that tonic striatal neurons may be involved in detecting stimuli predicting reward, regardless of the behavioral contingency of those stimuli.