DIRECT PROJECTIONS FROM THE OROFACIAL REGION OF THE PRIMARY MOTOR CORTEX TO THE SUPERIOR COLLICULUS IN THE MACAQUE MONKEY

Employing anterograde axonal tracing combined with intracortical micro stimulation, we have revealed in the macaque monkey that the orofacial region of the primary motor cortex sends projection fibers to the dee p layers of the superior colliculus. The terminal site of these projec tion fibers was almost localized to the lateral part of the intermedia te gray layer at its rostral level, and spatially segregated from that of projection fibers arising from the frontal eye field. The results indicate the existence of a discrete tectal region related specificall y to the control of orofacial movements.