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

Abstract

Several studies in the past have demonstrated the existence of an Otolith-Ocular Reflex (OOR) in man, although much less sensitive than canal ocular reflex. The present paper 1 confirms these previous results. Nystagmic eye movements (L-nystagmus) appear in the seated subject during horizontal acceleration along the interaural axis in the dark for an acceleration level (1 m/s2) about ten times the perception threshold with a sensitivity of about 0.035 rad/m. When sinusoidal linear acceleration is combined with optokinetic stimulation, the recorded nystagmus slow phase velocity exhibits strong periodic modulation related to subject motion. This marked effect of linear acceleration on the optokinetic nystagmus (OKN) appears at a level (0.1 m/s2) close to the acceleration perception threshold and has a 4-fold higher sensitivity than L-nystagmus. Modulation of OKN can reach a peak-to-peak amplitude as great as 20 degrees/s for a given optokinetic field size it increases with the velocity of the optokinetic stimulus, i.e. with the slow phase eye velocity. In parallel with changes in OKN slow phase velocity, linear acceleration induces a motion related decrease in the perceived velocity of the visual scene and modifications in self-motion perception. The results are interpreted in terms of a mathematical model of visual-vestibular interaction. They show that sensory interaction processes can magnify the contribution given to the control of eye movements by the otolithic system and provide a way of exploring its function at low levels of acceleration.

Visuo-vestibular interaction in the reconstruction of travelled trajectories

“…However, in this case the perception of the visual stimulus is worse with than without vestibular stimulus: the translational component is often not (well) perceived. It is known that a strong vestibular stimulus can cause the temporary perceptual freezing of a moving visual pattern (Pavard and Berthoz, 1977;Buizza, Leger, Droulez, Berthoz, and Schmid, 1980), and recent studies found physiological evidence for reciprocal cross-modal inhibition (Wenzel, Bartenstein et al, 1996;Brandt, Bartenstein et al, 1998). Also, the vestibular stimulus we imposed can temporarily decrease the retinal flow by inducing a VOR eye movement in the same direction as the optic flow in the visual stimulus: this will strongly modify the retinal flow.…”

Linear Self Motion Perception

“…When subjects are submitted to horizontal linear oscillations along the Y axis, they exhibit horizontal nystagmic eye movements. Their slow phase velocity is closely correlated to the actual linear acceleration of the head with a sensitivity of about 15°/sec/g at 0.2 Hz Buizza et al, 1980), (see Fig. 10).…”

“…(From Berthoz et a1., 1975. ) movements in linear motion perception (see however, Buizza et al, 1979Buizza et al, , 1980. It is therefore quite urgent for experiments to be done in this field.…”

“…The influence of otoliths on eye movements in the dark can be studied by indirect methods, for example comparing the gain of the vestibulo-ocular reflex during rotations about the vertical and offvertical axis (~ee for a review: Benson, 1974) and by direct methods using pure otolithic stimulation (Jongkees and Philipzoon, 1962;Niven et al, 1966;McCabe, 1964;Buizza et al, 1979Buizza et al, , 1980. Constant rotations about a vertical Z axis evoke a horizontal nystagmus, the slow phase velocity of which decays regularly to 0 with lower frequencies (time constant about 15 sec).…”

“…In addition, both vestibularly and visually induced linear motion perception are accompanied by postural readjustments (Helmholtz, 1896;Fisher and Kornmuller, 1930;Lishman and Lee, 1973;Lestienne et al, 1977) and oculomotor effects Buizza et al, 1980). These motors effects will not be reviewed here but only mentioned for some particular theoretical considerations (see for a review: Berthoz et al, 1979).…”