Influence of artificial vestibular feedback on posture instability caused by asymmetric proprioceptive stimulation

Subjects kept a vertical posture, standing on a rigid support. Stability of a posture was estimated by the sizes of standard deviations (sigma) from average amplitudes of the subject's head fluctuation in respect to zero coordinates. To create a feedback on the vestibular input, transmastoidal bipolar galvanic stimulation was used. Changes of current in contour of feedback looked as linear function considering amplitude and velocity of the subject's head displacements. Varying the factors of feedback function, it was possible to reduce sigma for lateral sways increased (in comparison with their values at the quiet stance in the darkness) as a result of unilateral vibrating stimulation of m. gluteus medialis. The results specify inequality of "velocity" and "position" information for maintenance of vertical posture in different subjects. The results specify also the ability of the central nervous system (CNS) to revalue weights of various kinds of information entering via the same channel. The data confirm the hypothesis according to which galvanic vestibular input is capable to deliver in CNS and adequate information on the current orientation of the body. This information can be used for stabilization of a posture.