THE FUNCTIONS OF THE MEDIAL PREMOTOR CORTEX .1. SIMPLE LEARNED MOVEMENTS

We report several studies on the effects of removing the medial premot or cortex (supplementary motor area) in monkeys. The removal of this a rea alone does not cause either paralysis or akinesia. However, the an imals were poor at performing a simple learned task in which they had to carry out an arbitrary action: they were taught to raise their arm in order to obtain food in a foodwell below. They were impaired whethe r they worked in the light or the dark. They were impaired when they h ad to perform the movements at their own pace, but much less impaired when a tone paced performance. Monkeys with lesions in the anterior ci ngulate cortex were as impaired as monkeys with medial premotor lesion s at performing this task at their own pace. However, monkeys with lat eral premotor lesions were less impaired. We conclude that the medial premotor areas play a crucial role in the performance of learned movem ents when there is no external stimulus to prompt performance.