Movement-related activity in the premotor cortex of rhesus macaques

Two observations reported in this chapter support the proposition that these changes are functionally related to the limb movement, rather than any concomitant sensory stimulus: the changes of neuronal activity are more closely time-locked to the beginning of the movement than to the visuospatial cues that trigger the movement.

Abstract

Several recent reports have shown that the primate premotor cortex is a distinct cortical field that plays a specialized role in the cerebral control of movement. However, the definition of the premotor cortex has been the source of difficulty, and as the premotor cortex is currently defined, its role in motor control has been questioned seriously. It must be emphasized, however, that not all neurons in the premotor cortex are movement related. Some cells appear to be responsive to the sensory signals that guide movement, others appear to reflect the animal's preparation for movement based on such sensory cues, and still others appear to be modulated in anticipation of predictable environmental events or stimuli. For heuristic purposes, these patterns have been termed “signal-related,” “set-related,” and “anticipatory,” respectively. These activity patterns are not mutually exclusive— that is, they are often combined in individual cells. Two observations reported in this chapter support the proposition that these changes are functionally related to the limb movement, rather than any concomitant sensory stimulus: (1) the changes of neuronal activity are more closely time-locked to the beginning of the movement than to the visuospatial cues that trigger the movement, and (2) neuronal modulations occur when the limb is moved “spontaneously” in total darkness.