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Distribution of cerebellar and somatic lemniscal projections in the ventral nuclear complex of the Virginia opossum
Author(s) -
Walsh T. Myrick,
Ebner Ford F.
Publication year - 1973
Publication title -
journal of comparative neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.855
H-Index - 209
eISSN - 1096-9861
pISSN - 0021-9967
DOI - 10.1002/cne.901470402
Subject(s) - opossum , biology , thalamus , cerebellum , anatomy , nucleus , dorsal column nuclei , neuroscience , sensory system , cerebellar cortex , cortex (anatomy) , climbing fiber , cuneate nucleus
The distributions of cerebellar and somatic lemniscal projections to the ventral nucleus of the thalamus were compared in the opossum to determine the extent of overlap in the terminal field of these two fiber systems. Following lesions of these structures, the degenerated fibers were traced to the thalamus using the Fink‐Heimer technique. The results indicate that the cerebellum projects only to the rostral portion of the ventral nucleus, while the gracile and cuneate nuclei project to the caudal portion of the ventral nucleus. We conclude from comparing these two afferent fiber systems that there is no detectable overlap in the cerebellar and lemniscal projections to the ventral thalamic nucleus of the opossum. These results support the hypothesis that the single somatic sensory‐motor area of the opossum's cortex receive afferent fibers from at least two separate subdivisions of the ventral nucleus. Outside the border of the ventral nucleus, cerebellar and lemniscal projection fields do overlap, especially in a cell group just dorsal to the ventral posterior nucleus. This is a distinctly different type of organization of these afferent fiber systems. This cell group has recently been shown likewise to project to the parietal somatic sensory‐motor cortex. Since the mode of intracortical termination of this projection differs markedly from that of the VP and VAL projections, the somatic sensory‐motor cortex of the opossum can be said to receive fundamentally different projections from two thalamic regions both of which are recipients of both cerebellar and somatic‐lemniscal information.