Somatosensory stimulation enhances the effects of training functional hand tasks in patients with chronic stroke.

OBJECTIVE: To test the hypothesis that somatosensory stimulation would enhance the effects of training functional hand tasks immediately after practice and 1 day later in chronic subcortical stroke patients. DESIGN: Single-blinded and randomized, crossover study. SETTING: Human research laboratory. PARTICIPANTS: Nine chronic subcortical stroke patients. INTERVENTIONS: Three separate sessions of motor training preceded by (1) synchronous peripheral nerve stimulation (PNS), (2) no stimulation, or (3) asynchronous PNS. MAIN OUTCOME MEASURES: Time to complete the Jebsen-Taylor Hand Function Test (JTHFT time) and corticomotor excitability tested with transcranial magnetic stimulation. RESULTS: After familiarization practice, during which all patients reached a performance plateau, training under the effects of PNS reduced JTHFT time by 10% beyond the post-familiarization plateau. This behavioral gain was accompanied by a specific reduction in GABAergically mediated intracortical inhibition in the motor cortex. These findings were not observed after similar practice under the influence of no stimulation or asynchronous PNS sessions. CONCLUSIONS: Somatosensory stimulation may enhance the training of functional hand tasks in patients with chronic stroke, possibly through modulation of intracortical GABAergic pathways.