Stabilogram diffusion analysis and the vestibular system features

Abstract

The method of stabilogram diffusion analysis is discussed. It is known that the sta-bilogram diffusion functions for the frontal and sagittal directions are different and their logarithmic plot has a characteristic bend (critical point). It is assumed that this bend is associated with a change in the persistence behavior for different time intervals in the presence of feedback in the postural control system. The article considers possible de-pendence between the features of the stabilogram diffusion function in question and the existence of a dead zone in the signal of the vestibular apparatus. Models of posture sta-bilization for the frontal and sagittal directions are designed. These models use modified motion equations for an inverted pendulum stabilized by a PID controller based on posi-tional measurements. The control is supplemented with feedback from the model of the otolith organ, which has a dead zone. It is assumed that the signal of the vertical canal of the otoliths and semicircular canals are subthreshold and are not used by the motor con-trol system. The results of diffusion analysis for a set of representations of numerical model of a person's postural control are presented. The parameters of the control system are corrected through comparing the simulation results with subjects examination data. Numerical modeling has shown that the effect of the otolith organ when a healthy person is standing in the “feet shoulder width apart” position in the frontal plane is minimal or absent. Though in the sagittal plane there are values of the otolith signal gain at which the influence of these control components becomes noticeable. The presented modeling enables detection of the main directions for analyzing the relationship between the indi-cators of the stabilogram diffusion analysis and the features of the vestibular signals and other sensory modalities.