Influence of target distance and acceleration level on eye movements evoked by lateral acceleration steps

Lateral eye movements produced by linear acceleration along the inter-aural axis were studied in 6 normal subjects. They were seated upright, whole-body restrained, and were exposed to randomised rightward/leftward steps of 0.05 g. 0.1 g, 0.24 g of 600 ms duration. When viewing earth-fixed targets at 30, 60 or 280 cm from their eyes, mainly pure compensatory slow-phase eye movements were evoked at latencies around 50 ms measured for the closest viewing distances. At onset, slow-phase amplitude was modulated by acceleration and target distance. When the subjects were stationary and pursued moving targets at similar distances and accelerations, latencies around 140 ms were observed, and catch-up saccades were frequently made. From these experiments, we defined the dynamics of the otolith-ocular reflex for various levels of acceleration and viewing distances.