Reorganization of the receptive fields of spinocervical tract neurons following denervation of a single digit in the cat.

The effect of acute and chronic section of the digital nerves of a single toe on the organization of low-threshold, mechanoreceptive fields of lumbosacral spinocervical tract (SCT) neurons has been studied in adult cats anesthetized with chloralose. The immediate effect of sectioning the digital nerves of a single toe is to produce a patch of dorsal horn in the medial region of the ipsilateral lumbosacral cord in which SCT neurons lack any peripheral receptive field when gentle hair movement or light touch of glabrous skin are used as stimuli. Other SCT neurons in the region may lose only part of their receptive fields. Between 30 and 70 days later most of the affected SCT neurons have established receptive fields. These are mainly on somatotopically inappropriate areas of skin medially and laterally adjacent to the denervated region. A small proportion of SCT neurons form discontinuous receptive fields. The relative somatotopic organization within the affected region remains unchanged. As there is no sign of regeneration of the sectioned nerves the new receptive fields must result from a central reorganization of excitatory inputs to SCT neurons. It is concluded that chronic peripheral nerve section affects the anatomical and physiological mechanisms underlying the formation of light touch receptive fields of dorsal horn neurons in the lumbosacral cord of the adult cat, but that the resulting reorganization of receptive fields is spatially restricted.