Noisy galvanic vestibular stimulation improves postural stability under virtual reality perturbation by enhancing vestibular processing and multisensory integration

Noisy galvanic vestibular stimulation (nGVS) is a non-invasive neuromodulation technique that enhances vestibular inputs via stochastic resonance, thereby improving postural stability. However, it remains unknown whether nGVS can ameliorate virtual reality (VR)-induced visual-vestibular conflict, which arises from an incongruence between moving visual cues and the absence of corresponding vestibular motion signals during quiet standing. The underlying neural-muscular mechanisms through which nGVS may modulate such conflict warrant clarification. This study aimed to investigate the effects of nGVS on postural stability, muscle activation, and cortical activation in healthy individuals during upright stance under different visual conditions. Thirty healthy young adults participated in this study. Six standing trials involving 3 visual conditions (eyes-open, eyes-closed, VR) and 2 vestibular stimulation conditions (nGVS and sham stimulation) were randomly allocated to each participant. nGVS was delivered via electrodes placed over bilateral mastoid processes. A synchronized multimodal assessment was conducted, using force plates to measure the center of pressure (COP), surface electromyography to record muscle activity, and functional near-infrared spectroscopy to monitor hemodynamic responses in the frontoparietal cortex. Compared to sham stimulation, nGVS significantly improved postural stability and hip muscle co-activation under VR perturbation, as evidenced by reduced COP-related parameters (ps < 0.05), decreased muscle activity in the bilateral rectus femoris (left: p = 0.003; right: p = 0.018), left biceps femoris (p = 0.020), and reduced co-contraction indices (left: p = 0.026; right: p = 0.027). In the VR condition, nGVS concurrently leaded to significantly lower dorsolateral prefrontal cortex activation (left: p = 0.038; right: p = 0.047) and higher supramarginal gyrus activation (left: p = 0.048; right: p = 0.029). nGVS effectively mitigated VR-induced sensory conflict and enhanced postural stability. The underlying mechanism may involve the induction of stochastic resonance to optimize vestibular processing and multisensory integration, thereby reducing reliance on the hip strategy. Chinese Clinical Trial Registry (ChiCTR# 2300078910); Date of registration: December 20th, 2023.