Motor function of the monkey globus pallidus. 1. Neuronal discharge and parameters of movement.

In order to examine the role of the basal ganglia (BG) in the regulation of basic movement parameters, we recorded extracellularly from pallidal neurons in conscious monkeys during the performance of a sequential wrist movement task which was composed of a series of holds and ballistic jumps. The movement sequence was predictable and had to be performed within specified time restraints. We recorded the activity of 297 neurons whose discharges were related to the movement task. We included only neurons whose discharges were related to movements at or about the wrist joint by prior examination outside the behavioural paradigm. Each neuron discharged preferentially to one direction of movement at or about the wrist joint. No consistent correlation was found between neuronal discharge and initial joint position, static load application, amplitude of movement or velocity of movement. The mean onset of neuronal discharge was 2 ms after the onset of EMG activity. The findings implied little contribution from the pallidal neurons in the execution of the current movement or to the movement's parameters. The implications are that the basal ganglia are likely to be concerned with other aspects of movement control.