| Galvanic vestibular stimulation (GVS) is a technique in which small currents are delivered transcutaneously to the vestibular system through electrodes placed over the mastoid bones. The applied current alters the firing rates of the peripheral vestibular afferents, thereby impacting vestibular perception and posture control.; GVS leads to perceived changes in orientation with respect to gravity, giving rise to a compensatory sway response that attempts to keep the body aligned with this altered sense of vertical. Thus, GVS provides a means to control human posture. In order to test the effectiveness of GVS in a dynamic situation, we examined whether the sway response elicited by bipolar GVS could be used to counteract sway caused by a mediolateral platform translation. With stabilizing GVS, all subjects showed significant reductions in both sway amplitude and sway latency, and therefore maintained a more erect stance and followed the platform displacement more closely. As a first step towards extending this work to include sway in arbitrary directions, we also examined whether monopolar GVS is as effective in producing anteroposterior sway as bipolar GVS is effective in producing mediolateral sway. We found that stochastic monopolar GVS can lead, in some cases, to anteroposterior COP displacement.; It has been shown that input noise can enhance the response of certain nonlinear systems to weak stimuli via a mechanism known as stochastic resonance. We examined whether sub-threshold stochastic monopolar GVS could enhance the sensitivity of the vestibular system and result in an increase in the relative stability of a subject's postural control system during a time-varying mechanical perturbation. We examined the relative stability of each subject's postural control system for trials with stochastic monopolar GVS and trials without GVS. Across the population, subjects had increased relative stability during trials with stochastic GVS, compared to trials without GVS.; In a clinical setting, GVS could possibly be used as the basis for a device that could provide a non-intrusive way to aid patients with vestibular disorders or balance difficulties by providing a means to enhance and/or control their balance. |
