An anatomical investigation of the corticopontine projection in the primate ( Saimiri sciureus). The projection from motor and somatosensory areas

Abstract

Lesions were made in motor and somatosensory areas of the cerebral cortex of squirrel monkeys, and the ensuing degeneration in the pontine nuclei was studied with the Fink and Heimer method modified by Wiitanen. The cortical areas studied projected on longitudinal columns in the pontine grey. A projection column receiving fibres from the supplementary motor area was situated most medially. It was followed laterally by a column receiving afferents from the precentral motor cortex. The postcentral cortex projected somewhat laterally and overlapped partially with the projection from the precentral cortex. The projection from fore- and hindlimb areas of both pre- and postcentral cortex overlapped to a large extent. The column receiving an input from the second somatosensory cortex was situated most laterally. With cortical lesions of comparable size the density of degenerating terminals was heaviest in the targets of the peri-Rolandic cortex, somewhat less intense in the projection from the second somatosensory cortex, and lowest in the projection from the supplementary motor area. The results were compared with those obtained in other mammals and discussed in relation to motor control.