Self‐Controlled Reorienting Movements in Response to Rotational Displacements in Normal Subjects and Patients with Labyrinthine Disease

Subjects seated in a Barany chair with head restrained were passively displaced in darkness away from a resting position. The displacements had raised cosine velocity profiles with peak velocities of 30"/second and 60"/second and amplitudes varying from 30" up to 180" in 30" intervals. The stimuli were delivered in the rightwards and leftwards directions in a Latin square design. Following each displacement and still in darkness, the subjects were required to rotate themselves accurately back to the starting position using a directionally congruent steering wheel which gave a velocity demand to the chair motor. Following each perturbation, when the subjects said that they were satisfied with their response, the lights were turned on so that they could make corrective adjustments back to center. The subjects were given an initial practice session. Normalsubjects consisted of 6 male and female subjects with an age range of 20 to 62. Subjects with unilateral loss of labyrinthinefunction included patients with vestibular nerve section for intractable vertigo and patients with acoustic neurinectomies. The patients were studied one week to one year postoperatively. Some were tested longitudinally.