Pattern of peripheral deafferentation predicts reorganizational limits in adult primate somatosensory cortex.

Previous experiments have shown that the reorganization of the hand representations in areas 3b and 1 of somatosensory cortex of monkeys can be extensive or limited, depending on the pattern of peripheral sensory loss. After the loss of two or more digits, the deprived zones of cortex are not fully reactivated by remaining inputs from the hand (Merzenich et al., 1984). In contrast, after deafferentation of the entire glabrous surface of the hand, the deprived cortex becomes responsive throughout its extent to cutaneous stimulation of the dorsal hairy surface of the hand (Garraghty and Kaas, 1991). To test the hypothesis that it is the pattern of sensory loss and not the deprivation procedure that results in these differences, we mimicked multiple-digit amputation by deafferenting corresponding parts of the dorsal and ventral hand. We then recorded from areas 3b and 1 of 3 squirrel monkeys 3-11 months after the deafferentation. In each case, much of the cortex normally activated by the removed inputs remained unresponsive to cutaneous stimulation of skin surfaces of the hand with intact innervation. Thus, the reorganization that can occur in somatosensory cortex following peripheral sensory loss is constrained by the precise content of the stimulus deprivation; that is, there is a limit to the set of new receptive fields cortical neurons can acquire.