Effect of Differences in Polarity on Cerebral Blood Flow during and after Galvanic Vestibular Stimulation: fNIRS Study

Abstract

[Purpose] The purpose of this study was to investigate the effect of differences in polarity on cerebral blood flow during and after galvanic vestibular stimulation using functional Near-Infrared Spectroscopy (fNIRS). [Participants and Methods] The participants were 20 right-handed young healthy adults who were observed under four stimulus conditions: 1) left anode/right cathode Galvanic Vestibular Stimulation (RC-GVS), 2) RC-sham, 3) right anode/left cathode GVS (LC-GVS), and 4) LC-sham. We monitored and compared cerebral oxyhemoglobin changes (oxy-Hb) using fNIRS before (T1: 0–60 sec), during (T2: 60–120 sec, T3: 120–180 sec) and after (T4: 180–240 sec, T5: 240–300 sec) bipolar GVS. [Results] In RC-GVS, oxy-Hb in the right temporal area significantly increased during and after GVS. In LC-GVS, oxy-Hb in both temporal areas significantly increased or had a tendency to increase during and after GVS. [Conclusion] Our results for brain regions activated during GVS are consistent with those of previous studies. It is possible that brain activation after GVS is related to after effect.