Role of cerebral cortex in voluntary movements. A review.

Findings from studies using electrical stimulation of cortex, recording from single neurons in awake animals, and measuring regional cerebral blood flow in humans have revealed some specific motor functions for several cerebral cortical areas. These areas include primary motor cortex, supplementary motor area, premotor area, parietal areas 5 and 7, and prefrontal area. Execution of movement is a function of the primary motor cortex, which translates program instructions for movement from other parts of the brain into signals. These signals encode variables of movement, such as the muscles to contract and the force and timing of their contraction. Long-latency reflex responses of muscles to stretch and cutaneous stimulation are also mediated by the motor cortex; other motor areas seem to perform higher order motor functions. The supplementary motor area controls input-output coupling in motor cortex and the programming of complex sequences of rapidly occurring discrete movements, such as playing the piano. The premotor area participates in the assembly of new motor programs. The parietal areas 5 and 7 are involved in directing attention to objects of interest in visual space and issuing commands for arm movements and eye movements to these objects. The prefrontal cortex performs cognitive functions, such as short-term memory of correct motor responses in delayed response tests.