Unexpected reorganization of somatosensory cortex in a raccoon with extensive forelimb loss.

Electrophysiological recordings were made from primary somatosensory cortex in a raccoon that had suffered a traumatic amputation of the forearm some time prior to its capture. Neurons in the affected forepaw region of sensory cortex were not silent but responded to cutaneous or neuroma activation of the remaining forearm stump. In addition, cells at many sites were responsive to tactile stimulation of the glabrous skin of the hindpaw ipsilateral to the damage. This indicates that the cortical plasticity following peripheral nerve damage can occur over much larger regions of cortex than was previously thought. An unmasking of silent thalamocortical terminals is not likely to be the mechanism underlying this plasticity in the raccoon.