Postural stability on moving platform oscillating at high frequencies. Effect of vestibular lesion.

The effect of linear perturbation at a frequency range of 8 to 24 Hz on postural stability was studied in 7 patients with unilateral vestibular function loss. Force platform technique was used with automatic analysis resulting in the sway velocity of the center point of force. In all patients the support surface movement produced increased sway velocity which was significantly greater than in the controls. Tests at lower frequencies (8 and 10 Hz) produced higher sway velocities than tests at higher frequencies (12, 14, 16 and 24 Hz). The results indicate that the vestibular system controls postural reflexes at a substantially higher frequency range than hitherto suggested.