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. Author manuscript; available in PMC: 2016 Jun 9.
Published in final edited form as: Med Biol Eng Comput. 2009 Mar 27;47(9):921–929. doi: 10.1007/s11517-009-0477-5

Fig. 3.

Fig. 3

Time series and corresponding time-varying spectra [or time-frequency distribution (TFD), bottom plot] of postural sway from an example subject (Adapted from [24]). The support surface angle (SS) is sway-referenced (SR) during the period 60–120 s. After rapidly returning to a fired support surface within 1 s (denoted by the double vertical dotted lines at 120 s), body sway oscillations at ~ 1 Hz develop (bright band in the TFD around 1 Hz for t > 120 s), indicative of inadequate sensory re-weighting. Boxed areas in the TFD correspond to time-frequency regions of interest for which energy ratios (ER) of high-frequency (0.7–1.3 Hz) to low-fiequency (0.1–0.7 Hz) energy were analyzed; numbers above the box reflect the ER values