Effect of Transcranial Direct Current Stimulation on Cortico-Muscular Coherence and Standing Postural Steadiness

Anirban Dutta and Sanjay Chugh

Keywords

noninvasive brain stimulation, stabilogram, corticomuscular coherence, postural steadiness

Abstract

Background: Non-invasive brain stimulation (NIBS) such as transcranial direct current stimulation (tDCS) is a promising tool for inducing cortico-spinal excitability and facilitating motor learning. The objective of this study was to investigate the effect of transcranial DC stimulation (tDCS) on cortico-muscular coherence and standing postural steadiness. Methods: In this single-blind, sham-controlled study, ten healthy subjects were evaluated under two conditions – with anodal tDCS and with sham tDCS. The change in cortico-spinal excitability was tested with single pulse transcranial magnetic stimulation (TMS). Paired t-test was performed on their cortico-muscular coherence measures and stabilogram metrics during quiet standing with eyes closed. Results: Anodal tDCS induced statistically significant (P=0.001, N=40) cortico-spinal excitability, 45min and 60min after the end of tDCS as revealed by single pulse transcranial magnetic stimulation (TMS) of resting tibialis anterior muscle. Furthermore, anodal tDCS induced statistically significant (P=0.001, N=40) cortico-muscular coherence in tibialis anterior muscle during quiet standing with eyes closed, 45min and 60min after the end of tDCS. The % change in the stabilogram metrics after anodal tDCS during quiet standing with eyes closed showed that anodal tDCS strongly (P=0.0000) affected the change in centroid of CoP data-points in medio-lateral direction (%CoPML) at 45min and 60min after tDCS session. Anodal tDCS had moderate effect (P=0.0113) on the change (decrease) in the path length of CoP trajectory (%CoPPL) at 60min after tDCS. Also, anodal tDCS had a strong (P=0.0000) effect on the change (decrease) in sway area (%CoPEA) at 45min and 60min after tDCS session. Conclusions: The preliminary results showed tDCS-induced increase in cortical excitability of tibialis anterior muscle as well as an improvement in standing postural steadiness during quiet standing with eyes closed. In our opinion, this is the first study to show that standing postural steadiness during eyes closed condition can be improved with tDCS.

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