Reorganization of cortical representations of the hand following alterations of skin inputs induced by nerve injury, skin island transfers, and experience.

Tactile experiences remodel the central nervous system representations of the body surface. The results of assessments of ten peripheral manipulations that reveal different aspects of representational plasticity are reviewed: (1) chronic peripheral denervation; (2) surgical amputation; (3) digital syndactyly and its natural behavioral equivalents; (4) peripheral nerve crush with reinnervation; (5) peripheral nerve transection and repair, with reinnervation; (6) denervation of very large skin surfaces, for very long times; (7) electrical stimulation of large-fiber afferents in the median nerve, simulating electroacupuncture; (8) implantation of always-innervated island pedicle flaps; (9) behavioral training with locationally invariant stimuli; and (10) behavioral training with moving stimuli. Focus is on the changes recorded in a primary somatosensory cortical field, area 3b, following these ten manipulations, in adult monkeys. On the basis of these findings, the following are discussed: (1) how altered schedules of activity from the skin contribute to cortical representational remodeling; (2) other factors that influence the representational remodeling; (3) where the remodeling actually occurs; and (4) some implications of these findings for sensory rehabilitation.