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 magnitudes and directions of postural responses were registered as changes in the center of foot pressure (COP) with a force platform. Vestibular stimulation consisted of 1 mA, binaural, bipolar galvanic current and proprioceptive input from tibialis anterior or soleus muscles was altered vibratory stimulation. The body lean induced by combined vibratory and galvanic stimulation could be largely considered as a summation of responses evoked by the galvanic and vibratory stimulation alone. The results of the present study showed that both vestibular and proprioceptive signals play important roles in the estimation of internal representation of the body vertical.