Projection of the external cuneate nucleus onto the cerebellum in the cat: An experimental study using silver methods

Abstract

Electrolytic lesions of the external cuneate nucleus with some involvement of neighboring structures were made in four adult cats. Two normal animals, two submitted to "phantom operations," and five experimental ones with lesions escaping the external cuneate nucleus, served as controls. Approximately serial sagittal sections through the cerebellum were treated according to the Nauta (44) method, some according to the methods of Glees (30) and Reumont and Lhermitte (48). The distribution of degenerating fibers in the cerebellum was mapped, and their mode of termination studied. The degeneration interpreted as a result of the lesion of the external cuneate nucleus was confined to two areas, ipsilaterally, one anteriorly and one posteriorly. The anterior area comprised Larsell's lobule V, the anterior part of VI, and possibly the posterior part of IV. The posterior area included the pars posterior and the most anterior folium of the pars anterior of the paramedian lobule, as well as the folia in the depth of the fissura prepyramidalis, possibly including all folia of sublobule VIII A. Since the external cuneate nucleus receives dorsal spinal root afferents from C 1 to T 8 these cerebellar areas receive impulses from neck, forelimb, and upper part of the trunk. The terminal areas rorrespond rather well to the "forelimb areas" determined by physiological methods by several authors. The neurons of the external cuneate nucleus terminate as mossy fibers. © 1962.