NOISE-INDUCED TRANSITIONS IN HUMAN POSTURAL SWAY

Correlation functions with multiple scaling regions occur in the descr iption of the fluctuations in the center of pressure during quiet stan ding. Postural sway is modeled as an inverted pendulum with a delayed feedback constructed such that for deviations beyond a spatial thresho ld a constant restoring force is engaged. In the absence of noise, two stable limit cycles coexist. The correlation function depends on the added noise intensity: at intermediate noise levels three scaling regi ons appear whereas only two occur for high noise levels. Our observati ons suggest that correlation functions with multiple scaling regions r eflect noise-induced transitions in bistable dynamical systems.