A neurophysiological study of the premotor cortex in the rhesus monkey

The frontal agranular cortex consists of at least three major subdivisions: the precentral motor cortex, the supplementary motor cortex, and the premotor cortex. Of these, the premotor cortex is by far the least intensively studied by neurophysiological methods in spite of recent evidence that it is important in higher order aspects of the cerebral control of movement ( Moll and Kuypers , 1977; Roland et al., 1980b ; Halsband and Passingham , 1982). We have accordingly studied neuronal activity in the premotor cortex of Rhesus macaques operantly conditioned to perform a visually guided motor task. We have concluded that many premotor cortex neurons appear to reflect motor set. Further, these and other premotor cortex neurons show activity patterns during and before the execution of an abstractly guided movement that are strikingly similar to what has been observed in association with movements made directly to visuospatial targets. Finally, a functional relationship of some premotor cortex unit activity to the execution of voluntary movement is supported by its close temporal correlation with the onset of movement, a significant correlation with the acceleration of the limb in some cases, and a uniform specificity for movement execution rather than the visuospatial cues that guide the movement.