motor area, a portion of the cerebral cortex that includes the precentral gyrus and the posterior part of the frontal gyri and that causes the contraction of the voluntary muscles on stimulation with electrodes. Normal voluntary activity requires associations between the motor area and other parts of the cortex; removal of the motor area from one cerebral hemisphere causes paralysis of voluntary muscles, especially of the opposite side of the body. Various parts of the motor area are associated with different body structures, such as the lower limb, the face, the mouth, and the hand. The parts associated with more delicate, complicated movements, such as those of the hand, are larger than those associated with more general movements.
