The monkey globus pallidus: neuronal discharge properties in relation to movement.

1. Recordings were made of the natural discharges of 388 pallidal neurones in awake, free-to-move monkeys in order to describe the discharge properties of such neurones in relation to normal movement performance. 2. Of the 388 neurones, 156 discharged only in association with one direction of movement of the forelimb about a specific joint. If that movement was not taking place the neurone would not discharge. 3. All joints and directions of movement for the upper limb were represented by clusters of cells within the pallidal population. 4. Twenty-nine per cent of neurones co-varied with movement of both contralateral and ipsilateral limb for the same direction of movement about a given joint; distal movements were represented with similar frequency to proximal movements in this group. 5. Afferent information provided by natural stimulation of peripheral receptors did not directly influence either the discharging or non-discharging pallidal neurones. 6. Movement related neurones were regionally organized and were found in the posterior part of the pallidum.