Relation between perception of vertical axis rotation and vestibulo-ocular reflex symmetry

Subjects seated in a vertical axis rotation chair controlled their rotational velocity by adjusting a potentiometer. Their goal was to null out pseudorandom rotational perturbations in order to remain perceptually stationary. Most subjects showed a slow linear drift of velocity (a constant acceleration) to one side when they were deprived of an earth-fixed visual reference. The amplitude and direction of this drift can be considered a measure of a static bias in a subject's perception of rotation. The presence of a perceptual bias is consistent with a small, constant imbalance of vestibular function that could be of either central or peripheral origin. Deviations from perfect vestibulo-ocular reflex (VOR) symmetry are also assumed to be related to imbalances in either peripheral or central vestibular function. We looked for correlations between perceptual bias and various measures of vestibular reflex symmetry that might suggest a common source for both reflexive and perceptual imbalances. No correlations were found. Measurement errors could not account for these results since repeated tests in the same subjects of both perceptual bias and VOR symmetry were well correlated.