Lesion-induced plasticity in the second somatosensory cortex of adult macaques.

We have reported that elimination of the representation of any body part in the primary (i.e., postcentral) somatosensory cortex of the adult macaque selectively eliminates the representation of that same body part in the second somatosensory area SII. We now report that, although removal of the entire postcentral hand representation does indeed leave the SII hand representation unresponsive to somatic stimulation initially, 6-8 weeks later this cortex is no longer silent. Instead, most or all of the region that had been vacated by the hand representation is now found to be occupied by an expanded foot representation. This massive somatotopic reorganization, involving more than half the areal extent of SII, exceeds that previously observed in the postcentral cortex after peripheral nerve damage and may reflect a greater capacity for reorganizational changes in higher order than in primary sensory cortical areas.