CEREBROCORTICAL PROJECTION OF HYPOGLOSSAL AFFERENTS

Afferent fibers are present in the distal portion of the hypoglossal nerve of M. mulatta. Since nothing is known regarding the projections established by these fibers, the present experiments were designed to determine whether stimulation of the hypoglossal nerve evoked potentials in the cerebral cortex. The results suggested that hypoglossal afferents project to a restricted region of the contralateral cerebral cortex. The responsive zone included the classically recognized area of lingual sensorimotor representation on the precentral and postcentral gyri. No ipsilateral projection could be detected. Since sectioning C2 or C3 dorsal root, or both, on the side ipsilateral to the nerve stimulation caused the evoked cortical response to disappear, we concluded that the afferents producing the potentials reached the central nervous system via the cervical dorsal roots and not via the hypoglossal nerve. These afferents project rostrally in the ipsilateral dorsal funiculus. © 1969.