Figure 6.

Schema shows the motor homunculus. At the high convexity, lower-extremity motor function extends onto the medial hemisphere anterior to the central sulcus. Motor function is arranged somatotopically, with lower face and voice motor control at the inferior margin of the central sulcus. Injury to the motor cortex results in a contralateral deficit except at the forehead, which is bilaterally innervated; therefore, unilateral injury does not result in paralysis. (The color coding corresponds to the coloring of the corticospinal tracts seen in Figs 10–12: leg = yellow, pink = shoulder, blue-green = hand, light gray = upper face, light blue = lower face, purple = tongue and pharynx.)