Motor Skill Acquisition and Retention after Somatosensory Electrical Stimulation in Healthy Humans.

Menno P Veldman,Nicola A Maffiuletti,Inge Zijdewind,Tibor Hortobágyi

doi:10.3389/fnhum.2016.00115

Abstract

Somatosensory electrical stimulation (SES) can increase motor performance, presumably through a modulation of neuronal excitability. Because the effects of SES can outlast the period of stimulation, we examined the possibility that SES can also enhance the retention of motor performance, motor memory consolidation, after 24 h (Day 2) and 7 days (Day 7), that such effects would be scaled by SES duration, and that such effects were mediated by changes in aspects of corticospinal excitability, short-interval intracortical inhibition (SICI), and intracortical facilitation (ICF). Healthy young adults (n = 40) received either 20 (SES-20), 40 (SES-40), or 60 min (SES-60) of real SES, or sham SES (SES-0). The results showed SES-20 increased visuomotor performance on Day 2 (15%) and Day 7 (17%) and SES-60 increased visuomotor performance on Day 7 (11%; all p < 0.05) compared with SES-0. Specific responses to transcranial magnetic stimulation (TMS) increased immediately after SES (p < 0.05) but not on Days 2 and 7. In addition, changes in behavioral and neurophysiological parameters did not correlate, suggesting that paths and structures other than the ones TMS can assay must be (also) involved in the increases in visuomotor performance after SES. As examined in the present study, low-intensity peripheral electrical nerve stimulation did not have acute effects on healthy adults' visuomotor performance but SES had delayed effects in the form of enhanced motor memory consolidation that were not scaled by the duration of SES.

Highlights

Sensory input is critical for accurate motor performance
Manipulation of sensory input is widely used in motor learning and movement rehabilitation, for example, following a stroke (Wu et al, 2006; Conforto et al, 2007)
An active control group controlling for spatial specificity was not included because the spatial specific nature of Somatosensory electrical stimulation (SES) has already been shown in patients (Wu et al, 2006) and healthy participants (Koesler et al, 2008)

Summary

Introduction

Sensory input is critical for accurate motor performance. Impaired sensory input decreases motor function in monkeys (Pavlides et al, 1993) and humans (Gentilucci et al, 1997), inevitably contributing to a variety of movement disorders (Patel et al, 2014). Spinal interneurons act as integrators between the sensory input and motor output (Nielsen, 2004). There is a strong interaction between afference and efference through direct paths interconnecting the somatosensory cortices and the primary motor cortex (M1) in rodents (Manita et al, 2015) and humans (Jones, 1983). Manipulation of sensory input is widely used in motor learning and movement rehabilitation, for example, following a stroke (Wu et al, 2006; Conforto et al, 2007).

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Results