Responses of the pyramidal tract to stimulation of the baboon's motor cortex

Abstract

The arm area of the baboon''s precentral motor cortex was stimulated by brief surface-anodal pulses, and the discharge of the corticospinal tract (the "pyramidal tract waves") was recorded by an electrode resting on the dorsolateral surface of the cervical spinal cord. Some properties of the pyramidal tract waves were described, and studied in relation to the firing of single cortico spinal fibers. The later pyramidal tract waves (the "I waves") were almost exclusively due to a semi-synchronous repetitive discharge of the same fast cortico spinal fibers as those responsible for the initial wave (the "D wave"). Some problems concerning the origin and significance of the I waves were discussed.