PATTERN OF PERIPHERAL DEAFFERENTATION PREDICTS REORGANIZATIONAL LIMITS IN ADULT PRIMATE SOMATOSENSORY CORTEX

Previous experiments have shown that the reorganization of the hand re presentations in areas 3b and 1 of somatosensory cortex of monkeys can be extensive or limited, depending an the pattern of peripheral senso ry loss. After the loss of two or more digits, the deprived zones of c ortex are not fully reactivated by remaining inputs from the hand (Mer zenich 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 sur face of the hand (Garraghty and Kaas, 1991). To test the hypothesis th at it is the pattern of sensory loss and not the deprivation procedure that results in these differences,we mimicked multiple-digit amputati on by deafferenting corresponding parts of the dorsal and ventral hand . We then recorded from areas 3b and 1 of 3 squirrel monkeys 3-11 mont hs after the deafferentation. In each case, much of the cortex normall y activated by the removed inputs remained unresponsive to cutaneous s timulation of skin surfaces of the hand with intact innervation. Thus, the reorganization that can occur in somatosensory cortex following p eripheral sensory loss is constrained by the precise content of the st imulus deprivation; that is, there is a limit to the set of new recept ive fields cortical neurons can acquire.