Langevin equation as a model of COP sway

Static posturography is a method of analysis of the human postural control system, in which the center of pressure (COP) sway at quiet standing is investigated. In this study, the Langevin equation is used as a model of the COP sway. The solution of this equation is the probability density function P(r,t/r(t0),t0). For experimental data, it is possible to represent this function in the form of a histogram. In the wave vector space, the probability density function is represented by the characteristic function, containing full information about the distribution of the variable r - r(t0). For young, elderly and parkinsonian populations, for the excluded as well as for the included visual input, for short wave vector k, the experimental functions are shown to be wen approximated by the Gaussian theoretical functions. However, in these cases, for greater wave vectors, non-Gaussian properties of this variable are observed.