The horizontal vestibulo-ocular reflex gain during active and passive high-frequency head movements.

Patients with bilateral peripheral vestibular loss complain of varying degrees of oscillopsia and balance difficulties. Some are able to engage in sporting activities while others are completely disabled. An assumption that other inputs are available to the vestibulo-ocular reflex (VOR) enabling it to achieve some degree of visual stability during high-frequency head movement is reasonable. In this study, the gain of the horizontal vestibulo-ocular reflex in 10 healthy subjects was examined during active high-frequency head-on-body rotation (head free), and compared to high-frequency passive whole-body rotation (head fixed). A statistical difference in the gain (P < .002) was noted for all frequencies between the two groups. In those individuals undergoing passive whole-body high-frequency movements, the gain was observed to rise (above unity) with increasing frequency of rotation, while the gain during active head-on-body rotation remained close to 1.