Influence of electric somatosensory stimulation on paretic-hand function in chronic stroke.

OBJECTIVE: To test the influence of electric somatosensory stimulation on performance of the Jebsen-Taylor Hand Function Test (JTHFT), a widely used assessment of functional hand motor skills, by the paretic arm in patients with chronic stroke. DESIGN: Initially, patients trained for several sessions until reaching plateau performance on the JTHFT. Subsequently, they entered a crossover randomized study, designed to evaluate the influence of somatosensory stimulation on JTHFT performance. SETTING: A research laboratory. PARTICIPANTS: Nine patients with chronic stroke (>/=1.5 y) who acutely had marked weakness (paralysis of the upper extremity is evaluated as equal or below Medical Research Council [MRC] grade 2) followed by improvement to an MRC grade of 4.24+/-0.43 (range, 3.5-4.9) and Fugl-Meyer Assessment (FMA) score of 86.43%+/-2.02% at the time of testing. INTERVENTIONS: Two hours of electric somatosensory stimulation was applied to the (1) paretic hand, (2) paretic leg, or (3) no stimulation in different sessions, in a randomized order. MAIN OUTCOME MEASURE: The time required to complete the JTHFT was analyzed by using repeated-measures analysis of variance (ANOVA) with factors time (pre-, postintervention) and intervention (paretic hand, paretic leg, no stimulation) followed by post hoc testing. RESULTS: Significant effects of intervention and intervention by time interaction (P<.01) on JTHFT time was revealed by repeated-measures ANOVA. Post hoc testing documented improvements in JTHFT time with paretic hand stimulation alone (P<.005), an effect that appeared more prominent in subjects with lower FMA scores. CONCLUSIONS: Somatosensory stimulation applied to a paretic limb can benefit performance of a functional test in patients with chronic stroke. This result supports the proposal that electric sensory stimulation in combination with training protocols may enhance the benefit of customary neurorehabilitative treatments and possibly motor learning.

Prefrontal cortex asymmetry for memory encoding of words and abstract shapes.

Previous work suggested a differential contribution of prefrontal cortex (PFC) to successful encoding depending on the stimulus material. Here, we tested the hypothesis that encoding of words preferentially involves the left PFC, while encoding of nonverbal items (abstract shapes) relies on the right PFC. We used an experimental design that evaluated encoding of both words and abstract shapes in the same healthy volunteers. A transient virtual lesion of the left or the right PFC was elicited with transcranial magnetic stimulation (TMS) while subjects memorized verbal and nonverbal items. We found that encoding of verbal material was disrupted by left PFC stimulation, whereas encoding of nonverbal material was disrupted by right PFC stimulation. These results demonstrate a functionally relevant lateralization of prefrontal contribution for verbal and nonverbal memory encoding.