EFFECT OF THE BONE CONDUCTION SOUND ON THE VERTICAL STANDING OF PEOPLE WITH BILATERAL VESTIBULAR HYPOFUNCTION IN CHALLEHGING SENSORY CONDITIONS

Balance and spatial orientation impaired by bilateral vestibular hypofunction (BVH) or microgravity can be restored with the help of galvanic and vibration stimulation of the vestibular apparatus. The paper presents a study aimed at testing feasibility to improve spatial orientation of people with BVH using the bone conduction sound. Participants were young healthy people (n=34) and people with diagnosed BVH (n=24). Stabilometry was used to determine the trajectory length and area of the ellipse of the center of common pressure (CoP) in the following standing conditions: eyes open + solid surface (normal condition, OS), eyes closed + solid surface (CS), eyes open + foam rubber surface (OR), and eyes closed + foam rubber surface (CR). It was established that in the BVH group the bone conduction sound shortened the trajectory significantly in all sensory conditions. The CoP ellipse area decreased in the challenging standing conditions (CS, OR, CR). In healthy people, the bone conduction sound shortened the CoP trajectory when standing CS, OR and CR only. The positive effect of stimulation using the bone conduction sound in both groups is most probably based on the phenomenon of stochastic resonance. The fact that the vestibular function improved in the complicated sensory conditions primarily, can be associated with stimulation of the brain proprioceptors and an increased importance of the “egocentric” (longitudinal) body vertical.