Article

The statistical properties of the center of pressure (COP) change over time, and
-invariant methods of the COP analysis is not sufficient to monitor the changes.
Therefore, dynamic temporal information of the COP signals has been important in
assessing the postural stability. The purpose of this study was to evaluate the
characteristic pattern of time-frequency dynamics during the upright stance in
patients with unilateral vestibular dysfunction (UVD). This study included 20
dizzy patients with UVD and age-matched 20 control subjects without any
vestibular disorder. The COP signals were collected using a single standard force
platform and a spectral analysis including the time-frequency dynamics was
carried out on the basis of the maximum entropy method (MEM) by using a segment
time series analysis. The power spectral density (PSD) analysis exhibited an
exponential decreasing shape (1/f (-)(beta)) when plotted on a double logarithmic
scale. The average value of beta in the low frequency range of less than 1 Hz in
the UVD group was significantly lower than that in the control group (p < 0.05)
in the medial-lateral (ML) direction under eyes closed condition. In the segment
time series analysis, the peak frequency of the COP signals in the patients with
UVD gradually converged to the frequency range of 0.1-0.2 Hz in the ML direction
under EC condition. Our results suggest that the segment time series analysis of
the COP signals can derive a characteristic pattern related to the UVD. It may
indicate an increased reflexivity of the COP fluctuation by the UVD, resulting in
inducing the instability.
CI - Copyright (c) 2014. Published by Elsevier B.V.

Langue : ANGLAIS