The low threshold mechanoreceptor representation in the fasciculus gracilis was examined and compared with that in the postcentral gyrus. At lumbar levels of the fasciculus gracilis both deep and cutaneous mechanoreceptive afferents are intermingled in a topographic pattern determined by the segmental arrangement of afferents at the dorsal root entry zone. However, when the fasciculus gracilis is examined at cervical levels, only a cutaneous mechanoreceptor representation is present and the fibers have resorted so that the body surface is represented in a continuous areal fashion rather than by segments. It is suggested that these transformations in the submodality composition and topographic organization of dorsal column afferents are prerequisite to the differential distribution of neurons belonging to different submodality classes in the postcentral gyrus of the cerebral cortex.

Keywords:
Somatic sensory system, Spinal cord, Postcentral gyrus, Cutaneous representation, Deep sensibility, Fasciculus gracilis, Primates
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© 1972 S. Karger AG, Basel
1972
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