TDCS over left M1 or DLPFC does not improve learning of a bimanual coordination task.

Kathleen Vancleef,Raf Meesen,Hakuei Fujiyama,Stephan P Swinnen

doi:10.1038/srep35739

Kathleen Vancleef, Raf Meesen + Show 2 more

Open Access

https://doi.org/10.1038/srep35739

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Abstract

Previously, transcranial direct current stimulation (tDCS) over the primary motor cortex (M1) has resulted in improved performance in simple motor tasks. For a complex bimanual movement, studies using functional magnetic resonance imaging and transcranial magnetic stimulation indicated the involvement of the left dorsolateral prefrontal cortex (DLPFC) as well as left M1. Here we investigated the relative effect of up-regulating the cortical function in left DLPFC and left M1 with tDCS. Participants practised a complex bimanual task over four days while receiving either of five stimulation protocols: anodal tDCS applied over M1, anodal tDCS over DLPFC, sham tDCS over M1, sham tDCS over DLPFC, or no stimulation. Performance was measured at the start and end of each training day to make a distinction between acquisition and consolidation. Although task performance improved over days, no significant difference between stimulation protocols was observed, suggesting that anodal tDCS had little effect on learning the bimanual task regardless of the stimulation sites and learning phase (acquisition or consolidation). Interestingly, cognitive performance as well as corticomotor excitability did not change following stimulation. Accordingly, we found no evidence for behavioural or neurophysiological changes following tDCS over left M1 or left DLPFC in learning a complex bimanual task.

Highlights

In interhemispheric projections from DLPFC to contralateral M119,20
We aim to up-regulate the function of left DLPFC and left M1 with transcranial direct current stimulation (tDCS) to enhance the learning of a complex bimanual coordination task while considering the two phases of learning, i.e., acquisition and consolidation
For this purpose participants were randomly assigned to one of five experimental groups: (1) anodal tDCS over left DLPFC, (2) sham tDCS over left DLPFC, (3) anodal tDCS over left M1, (4) sham tDCS over left M1, and (5) behavioural tasks without tDCS (BEHAV)

Summary

Introduction

In interhemispheric projections from DLPFC to contralateral M119,20. A key function of the DLPFC is thought to integrate information maintained in working memory with the organization of upcoming actions[21,22]. We aim to up-regulate the function of left DLPFC and left M1 with tDCS to enhance the learning of a complex bimanual coordination task while considering the two phases of learning, i.e., acquisition and consolidation For this purpose participants were randomly assigned to one of five experimental groups: (1) anodal tDCS over left DLPFC (aDLPFC), (2) sham tDCS over left DLPFC (sDLPFC), (3) anodal tDCS over left M1 (aM1), (4) sham tDCS over left M1 (sM1), and (5) behavioural tasks without tDCS (BEHAV). Subjective experiences of stimulation and potential confounding variables like sleep and caffeine consumption were questioned in daily questionnaires to account for the effects of non-experimental variables To this end, we hypothesized that the effect of tDCS over left DLPFC and left M1 on bimanual performance would depend on the task difficulty and the phase of learning. Left M1 stimulation would improve the performance in easy conditions in both skill acquisition and consolidation, but improvement of more difficult conditions would be only evident in the consolidation phase

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