MODIFICATION OF HUMAN POSTURAL RESPONSE TO LEG MUSCLE VIBRATION BY ELECTRICAL VESTIBULAR STIMULATION

In order to understand proprioceptive and vestibular contributions to human stance posture, the effect of electrical vestibular stimulation on body lean induced by leg muscle vibration was investigated. The mag nitudes and directions of postural responses were registered as change s in the center of foot pressure (COP) with a force platform. Vestibul ar stimulation consisted of 1 mA, binaural, bipolar galvanic current a nd proprioceptive input from tibialis anterior or soleus muscles was a ltered vibratory stimulation. The body lean induced by combined vibrat ory and galvanic stimulation could be largely considered as a summatio n of responses evoked by the galvanic and vibratory stimulation alone. The results of the present study showed that both vestibular and prop rioceptive signals play important roles in the estimation of internal representation of body vertical.