EYE-MOVEMENTS INDUCED BY LATERAL ACCELERATION STEPS - EFFECT OF VISUAL CONTEXT AND ACCELERATION LEVELS

Eye movement responses were obtained from six normal subjects exposed to randomly ordered right wards/leftwards linear acceleration steps of 0.05 g, 0.1 g or 0.24 g amplitude and 650 Ins duration along the inte l-aural axis, With the instruction to gaze passively into the darkness , compensatory nystagmus was evoked with slow-phase velocity sensitivi ty of 49 degrees s(-1) g(-1). When subjects viewed earth-fixed targets at 30 cm, 60 cm or 380 cm, eye movements at 130 ms from motion onset were proportional to acceleration and inversely proportional to target distance, before the onset of visually guided eye movements. Our resu lts show that a modulation with viewing distances of the earliest huma n otolith-ocular reflexes occurs in tile presence of pure linear accel eration. However, full compensation was not attained for the nearer ta rgets and higher accelerations.