Abstract
Sensory feedback is critical for motor learning, and thus to neurorehabilitation after stroke. Whether enhancing sensory feedback by applying excitatory repetitive transcranial magnetic stimulation (rTMS) over the ipsilesional primary sensory cortex (IL-S1) might enhance motor learning in chronic stroke has yet to be investigated. The present study investigated the effects of 5 Hz rTMS over IL-S1 paired with skilled motor practice on motor learning, hemiparetic cutaneous somatosensation, and motor function. Individuals with unilateral chronic stroke were pseudo-randomly divided into either Active or Sham 5 Hz rTMS groups (n = 11/group). Following stimulation, both groups practiced a Serial Tracking Task (STT) with the hemiparetic arm; this was repeated for 5 days. Performance on the STT was quantified by response time, peak velocity, and cumulative distance tracked at baseline, during the 5 days of practice, and at a no-rTMS retention test. Cutaneous somatosensation was measured using two-point discrimination. Standardized sensorimotor tests were performed to assess whether the effects might generalize to impact hemiparetic arm function. The active 5 Hz rTMS + training group demonstrated significantly greater improvements in STT performance {response time [F(1, 286.04) = 13.016, p < 0.0005], peak velocity [F(1, 285.95) = 4.111, p = 0.044], and cumulative distance [F(1, 285.92) = 4.076, p = 0.044]} and cutaneous somatosensation [F(1, 21.15) = 8.793, p = 0.007] across all sessions compared to the sham rTMS + training group. Measures of upper extremity motor function were not significantly different for either group. Our preliminary results suggest that, when paired with motor practice, 5 Hz rTMS over IL-S1 enhances motor learning related change in individuals with chronic stroke, potentially as a consequence of improved cutaneous somatosensation, however no improvement in general upper extremity function was observed.
Highlights
Motor recovery typically plateaus by 6 months after stroke (Hendricks et al, 2002), leaving 55–75% of individuals with chronic functional impairments of the hemiparetic arm (Gresham et al, 1995)
PRIMARY OUTCOME MEASURE Motor learning We examined the effect of 5 Hz Repetitive transcranial magnetic stimulation (rTMS) over ipsilesional S1 (IL-S1) paired with skilled motor practice of the Serial Targeting Task (STT) on motor performance across the 7 days of the experiment for both groups (Figure 2A)
Motor cortex excitability To determine whether the changes observed with 5 Hz rTMS over IL-S1 may be attributed to altered ipsilesional M1 cortical excitability, we evaluated resting motor threshold (RMT) at baseline and retention
Summary
Motor recovery typically plateaus by 6 months after stroke (Hendricks et al, 2002), leaving 55–75% of individuals with chronic functional impairments of the hemiparetic arm (Gresham et al, 1995). Despite the neurological deficits after stroke, the capacity for motor learning persists (Boyd et al, 2009; Vidoni and Boyd, 2009; Meehan et al, 2011a). This has led to an interest in adjunct interventions to positively augment motor learning and further enhance functional recovery in chronic stroke. Inconsistent results may stem from a number of factors, including non-standardized stimulation location within and across experimental sessions, a failure to pair rTMS with a well-controlled motor learning task, and an Frontiers in Human Neuroscience www.frontiersin.org
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