Influence of otolithic stimulation by horizontal linear acceleration on optokinetic nystagmus and visual motion perception

Nystagmic eye movements could be recorded during subject horizontal acceleration along his/her interaural axis (L-nystagmus), for acceleration levels about 10 times the perception threshold, and with a sensitivity of about 0.035 rad/m. This result confirms the existence of an otolith-ocular reflex in man. When harmonic linear acceleration was combined with optokinetic (OK) stimulation, the recorded OK nystagmus showed strong periodic modulation related to subject motion. This effect appeared at acceleration level close to the perceptual threshold, and had a 4-fold higher sensitivity than L-nystagmus. In parallel with nystagmus modulation, acceleration induced a motion related modification of both the perceived velocity of the OK stimulus and self-motion perception. The results are interpreted in terms of a mathematical model of visuo-vestibular interaction.