Fig. 3.

Stimulus evoked sway. (A) Stimulus evoked sway in the time domain for the three visual conditions (columns) and the four stimulus amplitudes (color coding); averages across 7 subjects and 10 cycles per subject. (B) Characterization of the stimulus evoked sway in terms of Bode histograms (gain and phase) and coherence functions across frequency. Gain gives the amplitude ratio between sway response amplitudes and tilt stimulus amplitudes. For a gain of one, the sway response amplitude equals the stimulus sway at the given frequency. A gain of zero indicates that the stimulus does not evoke any sway. Phase is a measure of the temporal relation between tilt stimulus and sway response. The body sway is in phase with the platform stimulus at 0° and is in counter phase at +/− 180°. Coherence is a measure of the signal to noise ratio of the stimulus evoked sway. (C) Averages of gain values (shown in B) across the Low, Mid, and High frequency ranges (columns) displayed for the peak-to-peak tilt stimulus amplitudes (abscissa) and for the three visual conditions. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)