Otolith stimulation evokes compensatory reflex eye movements of high velocity when linear motion of the head is...

Previous investigations have failed to find significant compensatory eye movements in response to linear motion of the head. However, the fact that visual acuity is essentially preserved during natural head movements, which combine both linear and angular components, is evidence that there must be compensation for linear translation. Hence we examined the lateral eye movements produced by angular oscillation, in the dark, in yaw at 0.5 and 1.5 Hz, 80 degrees/s peak, with the head both centred and positioned 30 cm eccentric from the axis of rotation in order to produce an additional linear acceleration acting tangentially. The combined stimuli produced high velocities of eye movement which were much greater than those produced by angular motion alone. The findings are evidence or a linear-compensatory reflex which is probably otolithic. The dependency of otolithic eye movements on concurrent stimulation of the semicircular canals is a possible explanation of positional nystagmus in neuro-otological disease in which it may be released by a pathological imbalance of canal function.