A. Feedback model for balance control of a single-segment, inverted-pendulum body with representation of external stimulation from support-surface rotation, GVS, and real-time feedback of GVS. B. FRF gain and phase data from an individual subject with model fit. Error bars show 95% confidence limits. C. Family of FRF gain curves (mean data from 12 subjects with normal vestibular function derived from pseudorandom surface-tilt stimuli that evoke ML sway) showing decreasing gains with increasing stimulus amplitude. D. Sensory weights for subjects with normal vestibular function (mean ± sd, N=8) and 4 subjects with bilateral vestibular loss estimated from fits to FRF data from pseudorandom surface-tilt stimuli that evoke anterior-posterior sway. Modified from [9,11].