Cells of origin of cortical projections to dorsal column nuclei, spinal cord and bulbar medial reticular formation in the rhesus monkey.

Cells of origin of cortical fibers to the dorsal column nuclei, spinal cord and bulbar medial reticular formation were identified in 8 rhesus monkeys by means of the horseradish peroxidase (HRP) retrograde transport technique. After dorsal column nuclei injections small pyramidal neurons were labeled in the contralateral hemisphere in layer V of areas 3, 1, 2 and 5 and in layer V of the posterior part of area 4. In contrast, after spinal cord injections many area 4 giant Betz cells in the contralateral hemisphere were labeled as well as many other layer V pyramidal neurons in areas 4 and posterior 6 and in areas 3, 1, 2 and 5. Injections in the bulbar medial reticular formation labeled mainly medium sized layer V pyramidal neurons in area 6 and the anterior part of area 4 of both hemipsheres.