Electrical vestibular stimulation for human standing balance and motion perception
Effects of stimulation arrangement and signal design
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Abstract
Vestibular information from both sides of the head converges within the vestibular nuclei to contribute to postural stabilization of the head and body, and to provide accurate perceptions of self-motion. It remains uncertain whether these responses are evoked through equivalent integration processes, because our perception of head position is not always aligned with postural responses evoked by vestibular perturbations, where postural responses are expected to align with head orientation. In this study, we examine if the contributions from bilateral vestibular organs are equal in postural responses and the perceptions of motion that are evoked during an artificial vestibular disturbance. This study also examines whether there is a linear integration of vestibular signals in the postural responses and perceived motion generated by the vestibular disturbance. Electrical vestibular stimulation (EVS) was used to evoke whole-body and compensatory ankle-muscle responses during a standing balance task or the sensation of angular velocity about a roll axis during a perceived motion task. Stimulation on one side (monaural) was used to demonstrate if individual leg muscles receive equal inputs from both labyrinths, and if the motion perceived by activity of each labyrinth is equivalent. Principles of left-right integration were evaluated by comparing the sum of monaural responses with stimulation on both sides (binaural).