Functional changes at periphery and cortex following dorsal root lesions in adult monkeys

Chronic peripheral nerve injuries produce neural changes at different levels of the somatosensory pathway, but these responses remain poorly defined. We selectively removed cutaneous input from the index finger and thumb in young adult macaque monkeys by lesioning dorsal rootlets to examine both immediate and long-term systemic responses to this deficit. Corresponding digit representations within somatosensory cortex (SI) were initially silenced, but two to seven months later again responded to cutaneous stimulation of the 'deafferented' digits. We remapped cutaneous receptive fields (RFs) within adjacent intact dorsal rootlets two to four months after lesioning. RF distributions had greatly expanded, so that rootlets previously innervating adjacent hand regions now responded to stimulation of the index finger and/or thumb. Thus our results demonstrate peripherally mediated central reorganization.