Sensory inputs contribution to vestibulo-ocular reflex and postural response maintaining simultaneously body balance

We investigated which sensor had dominant contribution to vestibulo-ocular reflex (VOR) and postural sway (PS) for the optimal body balance maintenance under conditions of visual or/and somatosensory input reduction. Healthy subjects were examined in upright stance on stable platform and foam rubber, under following conditions: in quiet stance with eyes open (EO) and closed (EC); during voluntary head movements in horizontal plane at frequency 0.2 - 0.3 Hz with EO (HO) and EC (HC). The results showed that PS increased smaller during HC than during HO on both supports stable and unstable, but particularly on the foam rubber. Mean gain of VOR induced by HO was 1.2 and this one evoked by HC was 0.9 on the two supports. Therefore, when in upright stance the vestibular input is stimulated, the reduction of either or both inputs visual and proprioceptive influences postural stability positively while VOR is affected negligibly. Hence, the vestibular contribution to both VOR and PS is dominant.