[A study on relation between premotor cortex and forelimb movement: analysis of neuronal activity].

The aim of this study is, first, to examine the existence of topographical organizations in the premotor cortex in monkeys trained rigorously to move his proximal and distal forelimb separately. The second aim is to observe premotor cortex neuronal activity in association with simple movement triggered by sensory signals of three different modalities (visual, auditory, and somatosensory). Premotor cortex was defined as the lateral part of frontal agranular cortex where intracortical microstimulation could not evoke muscle contraction at intensity below 50 microA. Neurons related to the distal forelimb movement formed three foci in the premotor cortex. Neurons related to the proximal forelimb movement distributed widely in the premotor cortex without forming any distinct focus. Movement-related premotor neurons showed less modulation of discharge frequency in association to the movement than motor cortex neurons, and some of them responded selectively to one or two sensory signals triggering the movement. These results suggests that premotor cortex contributes less directly to the execution of simple movements, but may play an important role in controlling or organizing complex movements.