Effects of different noisy galvanic vestibular stimulation frequencies on postural control responses

Noisy galvanic vestibular stimulation (nGVS) can improve postural stability by delivering subthreshold electrical noise to the vestibular system. However, the frequency-specific effects of nGVS on postural control responses-particularly those involving the center of mass (COM) recovery force and movement strategies-remain unclear. We investigated how different nGVS frequencies affect postural control, estimating COM fluctuations using a rigid pendulum model. Thirty-two healthy adults (mean age, 20.3 ± 1.2 years; 19 females) underwent three interventions: sham nGVS, low-frequency nGVS (LF-nGVS, 0-100 Hz), or high-frequency nGVS (HF-nGVS, 100-640 Hz), each with a 200 µA current (0 µA for the sham). During each 40-s trial, participants stood on a platform with eyes closed and the middle 30 s were analyzed. Inertial measurement units were affixed to the occipital protuberance to capture head kinematics. Postural control was assessed using conventional metrics (e.g., center of foot pressure [COP], COM sway, and head acceleration) and novel indicators of COM recovery force and head acceleration control based on motor strategies. Both LF-nGVS and HF-nGVS significantly reduced several indices, including COP velocity and head angular velocity, compared with sham stimulation. No significant differences were observed between LF-nGVS and HF-nGVS. Head acceleration was significantly correlated with COM recovery force and joint movement strategies in both stimulation conditions. Although the mechanism of neural network activity at different stimulation frequencies requires careful interpretation, these findings suggest that COM recovery and associated motor strategies contribute to nGVS-induced postural improvements, providing insights into its neuromechanistic effects.