Effects of Transcranial Electrical Stimulation to the Right Posterior Parietal Cortex on Physical Control Responses

Abstract

Abstract The posterior parietal cortex (PPC) plays an important role in postural stability by adapting to changes in input from the visual, vestibular, and proprioceptive systems. However, it is little known whether transcranial electrical stimulation (tES) of the PPC affects reactive postural responses. The purpose of this study was to investigate changes in physical control responses to anodal and cathodal transcranial direct current stimulation (tDCS) and transcranial random noise stimulation (tRNS) of the right PPC using a simultaneous inertial measurement unit. The joint movements of the lower limb of 33 healthy volunteers were measured while standing on a soft-foam surface with eyes closed, during various stimulation modalities. These modalities included anodal, cathodal tDCS, and sham stimulation in Experiment 1 and tRNS and sham stimulation in Experiment 2. The results showed that cathodal stimulation significantly decreased the joint angular velocity in the hip rotation, ankle inversion-eversion, and abduction-adduction directions compared to anodal or sham stimulation in Experiment 1. In contrast, there were no significant differences in physical control responses with tRNS stimulation in Experiment 2. These findings suggest that tES of the right PPC may modulate physical control responses; however, the effect depends on the stimulus modality.