Unilateral cathodal transcranial direct current stimulation over the parietal area modulates on postural control depending with eyes open and closed

Abstract

AbstractCathodal transcranial direct current stimulation (C-tDCS) is generally assumed to inhibit cortical excitability. The parietal cortex contributes to multisensory information processing in the postural control system, and this processing is proposed to be different between the right and left hemispheres and sensory modality. However, previous studies did not clarify whether the effects of unilateral C-tDCS of the parietal cortex on the postural control system differ depending on the hemisphere. We investigated the changes in static postural stability after unilateral C-tDCS of the parietal cortex. Ten healthy right-handed participants were recruited for right- and left-hemisphere tDCS and sham stimulation, respectively. The cathodal electrode was placed on either the right or left parietal area, whereas the anodal electrode was placed on the contralateral forehead. We evaluated static standing balance by measuring the sway path length, mediolateral (ML) sway, anteroposterior (AP) sway, sway area, and the sway path length per unit area (L/A) after 15-minute C-tDCS under eyes open (EO) and closed (EC) conditions. C-tDCS over the right hemisphere significantly increased the sway path length, ML sway, and sway area in the EO condition. In contrast, C-tDCS over the left hemisphere significantly increased the L/A in both the EC and EO condition. These results suggest that the right parietal region contributes to static standing balance through chiefly visual information processing during the EO condition. On the other hand, L/A increase during EC and EO by tDCS over the left parietal region depends more on somatosensory information to maintain static standing balance during the EC condition.