The distribution of degenerating fibers within the intralaminar nuclei was studied following lesions of the cerebral neocortex in Macaca mulatta, M. nemestrima, M. irus, Cercopithecus aethiops sabaeus and Saimiri sciureus. Degenerating fibers were revealed by the Nauta silver method. The cortex rostral to the central sulcus appeared to be the principal source of cortical fibers projecting to intralaminar nuclei. Very few degenerating fibers were observed in intralaminar nuclei following parietal, temporal or occipital lobe lesions. Efferent fibers of the prefrontal lobe terminated predominantly in paracentral and parafascicular nuclei. Premotor cortex projected mainly to central lateral and parafascicular nuclei. Motor cortex projected to central lateral and centromedian nuclei. The projection from motor cortex to the ventrolateral centromedian nucleus was topographically distributed, with fibers from leg area terminating lateral to those from arm area. Copyright © 1969 The Wistar Institute of Anatomy and Biology
