Characteristics of the Somatic Afferent Projection to the Precentral Cortex in the Monkey

¹ From the Laboratory of Physiology, Yale University School of Medicine, New Haven, and the Department of Neurophysiology, Institute of Living, Hartford, Connecticut

The afferent evoked electrical response in precentral and postcentral cerebral cortex was studied in anesthetized and unanesthetized monkeys. Responses to nerve volleys were obtained on both sides of the central sulcus, tactile evoked responses were limited to the contralateral postcentral gyrus. Precentral responses were evoked by stimulation of the fast cutaneous and slow muscle afferent fibers. The amplitude and distribution of precentral responses varied with the number of peripheral nerve fibers synchronously activated. The latency of precentral responses increased as a function of distance from the central sulcus. Precentral and postcentral potentials were altered in the same manner by topical application of Novocaine and strychnine and the spreading depression of Leão. The nature of the afferent precentral electrical response, the anesthetic conditions for its study and the possible functional role of this projection are discussed.

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