Non-linear analysis of stabilograms with alcoholic intake

Equilibrium function in the cerebellum (vestibulo-cerebellar system) can deteriorate under the influence of alcohol. In the Romberg posture, the center of gravity, which was measured every 50 ms by stabilometry, appeared to shift with alcohol ingestion. In the previous study, a locus in the center of gravity (stabilogram) was converted to values of statistical indices such as area of sway, total locus length, and locus length per unit area, although these indices could not always distinguish between the statokinesigrams sampled from seven healthy young males in sober and intoxicated states. This measurement was made with an AMTI force plate. In this study, "translation error" was estimated in a d-dimensional embedding space in order to compare statokinesigrams recorded before and after the ingestion of doubly diluted brandy in 30 s (1 ≤ d ≤ 10). We succeeded in validating a stochastic differential equation as a mathematical model of the body sway. The randomness in the model was preserved after alcohol intake and significantly increased in the medial/lateral direction. Visual information referred by the postural control system when standing might be interfered by the effects of intoxication, which was regarded as disturbance. This method is considered to be useful to diagnose the disorders of the vestibulocerebellar system.