Enhancing human balance control with galvanic vestibular stimulation

With galvanic vestibular stimulation (GVS), electrical current is delivered transcutaneously to the vestibular afferents through electrodes placed ove r the mastoid bones. This serves to modulate the continuous firing levels o f the vestibular afferents, and causes a standing subject to lean in differ ent directions depending on the polarity of the current. Our objective in t his study was to test the hypothesis that the sway response elicited by GVS can be used to reduce the postural sway resulting from a mechanical pertur bation. Nine subjects were tested for their postural responses to both galv anic stimuli and support-surface translations. Transfer-function models wer e fit to these responses and used to calculate a galvanic stimulus that wou ld act to counteract sway induced by a support-surface translation. The sub jects' responses to support-surface translations, without and with the stab ilizing galvanic stimulus, were then measured. With the stabilizing galvani c stimulus, all subjects showed significant reductions in both sway amplitu de and sway latency. Thus, with GVS, subjects maintained a more erect stanc e and followed the support-surface displacement more closely. These finding s suggest that GVS could possibly form the basis for a vestibular prosthesi s by providing a means through which an individual's posture can be systema tically controlled.