PROJECTIONS OF ANTERIOR ECTOSYLVIAN GYRUS TO THALAMUS, DORSAL COLUMN NUCLEI, TRIGEMINAL NUCLEI AND SPINAL CORD IN CATS

1. 1. Descending projections of the anterior ectosylvian gyrus (AEct) were studied with the Nauta-Gygax method of secondary degeneration on the basis of total and partial cortical removals in 11 cats. 2. 2. Thalamus. Degenerated fibers were traced to the posterior ventral, lateral ventral, reticular, anterior ventral, centralis lateralis, centre médian and the so-called posterior group nuclei. A somatotopic organization was found with respect to the projection into the posterior VP nuclei: anterior part of AEct to dorsolateral VPM (except for the most lateral region), middle part of AEct to medial division of VPL and the most lateral portions of VPM, posterior part of AEct to the lateral division of VPL. No somatotopic arrangement was found with respect to connections to other thalamic nuclei including the PO group. 3. 3. Pons and medulla oblongata. Degenerated fibers were found in the trigeminal nuclear complex and adjacent lateral reticular formation (anterior AEct), in the cuneate nucleus (middle AEct) and in the gracile nucleus (posterior AEct). The trigeminal projections were found mainly in the principal sensory nucleus and in the 'c' subnucleus of the oral division of the spinal trigeminal complex. 4. 4. Spinal cord. Degenerated fibers were found mainly in the cervical cord, and few at the thoracic and lumbar levels. They were traced to the basal layers of the contralateral dorsal horn. Very few fibers seem to end in the more dorsal layers of the dorsal horn or in the intermediate zone. No degenerated fibers were found ipsilaterally. © 1969.