Sensory-motor processing in the caudate nucleus and globus pallidus: a single-unit study in behaving primates

Monkeys were prepared for chronic recording of single neurons in the caudate nucleus (Cd) or globus pallidus (GP) during learned wrist flexion-extension movements triggered by visual and somatic sensory inputs. Almost two-thirds of GP cells and more than one-third of Cd cells modified their discharge during these tasks. Three categories of response types were observed. The first was movement related. The second type was event related, in which the cells responded to either the onset or offset of the sensory inputs regardless of the correcting movement direction. A third type combined elements of the first two categories and was termed complex. These cells responded to complex abstractions of the sensory-motor event. A latency analysis indicated that the majority of cells was not involved in initiating movements but may have participated in movement execution. The results of this experiment suggest that during voluntary movement the basal ganglia activity is correlated with motor outputs, sensory inputs, and perceptual abstractions of these sensory-motor events. As such the results are compatible with an influence by diverse regions of cerebral cortex on basal ganglia neurons during the movement control process.