Stabilometry during Horizontal Translation of Support Surface

Sway of the body's center of gravity (BCG) in an upright standing posture were studied during horizontal translation of the support surface using a specially designed stabilometer. The experiments were performed on 5 health subjects and 6 patients with unilateral labyrinthine disturbances. They stood on the support surface with their feet 10 cm apart, and the surface was moved at an amplitude of 10 cm at velocities of 2, 4, 6, 8 and 12cm/s, respectively. Backward, forward, rightward and leftward translation were examined with eyes open and closed. Under each test condition, one or three trials were performed. The superimposed and averaged results were displayed.Backward translation with 5 cm/s caused a forward displacement of the BCG with a latency of 20-30 ms (Responce 1, R1), a backward displacement with a latency of 30-45 ms after the onset of R1 (Responce 2, R2) and forward displacement with a large amplitude and a latency of 135-145 ms after R1 (Responce 3, R3) which indicated maximal displacement 145-255 ms after the onset of R3 (Responce 4, R4) and return to the original position before the onset of translation.Responses caused by forward, rightward and leftward translation were similar to the response of backward translation, except for R2 on right and left translation which provide unclear results.R2 and R3 were considered to be displacement due to spinal stretch reflex and dynamic labyrinthine reflex, respectively.Two patients with an intense decrease in caloric response in the affected labyrinth indicated a decrease in R3 induced by translation to the affected side.