Perceptual significance of somatosensory cortical reorganization following peripheral denervation

THE functional significance of reorganization in somatosensory cortex following peripheral denervation has not been thoroughly addressed. In this paper, two distinct hypotheses dealing with this issue are discussed. The first is the hypothesis of functional respecification. This influential view suggests that sets of partially deafferented cortical neurons, which respond to new peripheral inputs and acquire new receptive fields, undergo corresponding changes in perceptual meaning. Excitation of these neurons by stimulation of their novel receptive fields is thought to result in a change in referral of sensation from the original (now denervated) skin fields to the newly acquired skin fields. The second hypothesis is that of functional conservation. This equally plausible alternative is that sets of partially deprived neurons, although they respond to novel peripheral inputs, retain their original perceptual meaning. Excitation of these neurons by stimulation of their new receptive fields is thought to evoke sensation formerly mediated by those neurons, and hence is still projected to the original, now denervated skin regions or phantom. Behavioral evidence strongly suggests that cortical reorganization after peripheral denervation does not result in major functional respecification, but that the original perceptual function mediated by those neurons is preserved.