The effect of transcranial direct current stimulation of the motor cortex when swallowing / 中华物理医学与康复杂志

ABSTRACT

Objective To assess the neurophysiological effects of transcranial direct current stimulation (tDCS) of the motor cortex when swallowing.Methods Twenty healthy volunteers had anodal tDCS (a-tDCS), cathodal tDCS (c-tDCS) or sham tDCS applied over the hemisphere with stronger suprahyoid projections, effortful swallowing was performed simultaneously.Suprahyoid motor-evoked potentials (MEPs) on both the stimulated and non-stimulated contra-lateral hemisphere were examined immediately before stimulation and 5,30, 60 and 90 minutes later.The MEPs were normalized and analyzed using two-way repeated measures analysis of variance.Results The tDCS had long-lasting effects on the suprahyoid MEPs bilaterally.There were significant changes in the effect over time.Sham tDCS showed no significant effect.Compared with sham tDCS, a-tDCS significantly increased the excitability of the stimulated hemisphere, but not the non-stimulated projection.Compared with sham tDCS, c-tDCS induced decreased cortical excitability in the stimulated hemisphere but an increase in the non-stimulated projection.Conclusions tDCS during swallowing can alter bilateral swallowing activity in the motor cortex in a polarity-dependent and site-dependent way.A-tDCS enhances the excitability of the stimulated hemisphere while c-tDCS inhibits it ipsilaterally but increases it contralaterally.