The role of the basal ganglia in controlling a movement initiated by a visually presented cue.

This study examines the effects on single neurons in caudate nucleus and globus pallidus of a visual stimulus, which is a cue to begin a tracking movement involving the forelimb on the side contralateral to the recording site. The experiments were designed to examine the relationship between activity of single neurons in these structures and movement initiation. Four monkeys were prepared for chronic recording of single neurons. The animals were trained to perform a tracking task that involved flexion and extension of the wrist at the onset of visual cue. The activities of a large proportion of neurons examined were correlated with the task, the proportion being greater in globus pallidus than in caudate nucleus. The majority of correlated neurons were activated after the onset of muscle activity and subsequent movement. It is thus unlikely that these cells were involved in movement initiation. However a role in movement execution is not excluded by the results. The fact that many cells were responsive only to certain specific conditions of the visual cue trial suggests an influence on these cells by highly processed visual information from other brain areas.