SOMATIC RECEIVING AREAS OF CEREBRAL CORTEX OF SQUIRREL MONKEY (SAIMIRI SCIUREUS)

Abstract

The somatic receiving area of the semilissencephalic brain S. sciureus were mapped by means of the surface-positive potentials evoked by mechanical stimulation of the skin during deep Nembutal anesthesia. The representation in somatic afferent area I was similar to that previously reported for the macaque. The pattern may be visualized as an animal with its tail on the medial wall, face most laterally near the sylvian fissure, digits oriented rostrally and back caudally. The pre- and postaxial aspects of the leg are separated by the intervening foot area, as is continuity of the back. The representation of the head is split by the arm areas. Somatic afferent area II extends from the upper bank of the sylvian fissure (face) across the cortex overlying the insula in the superior limiting sulcus (arm) and onto the posterior insula (trunk and leg). A similar somatotopic specialization was found here as in the somatic sensory I pattern, with the largest area devoted to the arm. Approximately one-third of the cortex responsive to tactile stimulation is situated rostral to the "postcentral" granular cortex. It is suggested that this may be part of a complex tactile representation coextensive with the precentral motor pattern.