Article

Complexity is a new measure for identifying the adaptability of a complex system
to meet possible challenges. For a center of pressure (COP) time series, the
complexity measure represents the stability of postural control. In this study,
multiscale entropy (MSE) was used to evaluate the complexity of COP time series
in six test conditions of sensory organization test (SOT). Complexity index (CI)
is defined as the summation of entropies with coarse-graining scales 1-20 by MSE.
A total of 51 subjects belonging to 3 groups - healthy-young, healthy-elderly and
dizzy - were recruited in this study. The COP signals in both anteroposterior
(AP) and mediolateral (ML) directions were analyzed respectively. According to
our results, the CI of AP-direction COP time series is significantly correlated
to the equilibrium score, which represents the stability of postural control in
SOT. The AP-direction sway is significant larger than the ML-direction sway,
particularly in the test conditions with sway-surface. In additions, the CI of
AP-direction COP for the healthy-elderly and dizzy groups are significantly lower
than those for the healthy young group in the test conditions 1-4. The CI of
ML-direction COP for the healthy-elderly group is significantly lower than those
for the healthy-young and dizzy groups under test conditions 3 and 6. These
results show that the complexity loss is a common status of AP-direction COP time
series for both healthy-elderly and dizzy groups, and the complexity of
ML-direction COP time series for subjects with unilateral vestibular dysfunction
is higher than that for the healthy-elderly group specifically under test
conditions 3 and 6.
CI - Copyright (c) 2014 Elsevier B.V. All rights reserved.

Langue : ANGLAIS