Research paperTranslational otolith-ocular reflex during off-vertical axis rotation in humans

- The modulation of horizontal slow phase velocity during OVAR is larger at high frequency.
- The modulation of horizontal slow phase velocity during OVAR at high frequency is larger for near fixation distance.
- The modulation of horizontal slow phase velocity during OVAR represents a translational otolith-ocular response.

Two characteristics of otolith-ocular responses - linear vestibulo-ocular reflex and vergence - were examined during constant velocity off-vertical axis rotation (OVAR) in the dark. Sixteen subjects were rotated about their longitudinal axis when tilted 30° relative to the direction of gravity. Rotational velocities were 36 and 288/s corresponding to frequencies of 0.1 and 0.8 Hz, respectively. Subjects were asked to imagine stationary targets located at 0.5 m, 1 m, and 2 m in the straight-ahead direction. Binocular eye movements were recorded in the dark using infrared videography. The modulation of horizontal slow phase velocity during OVAR was larger at 0.8 Hz than at 0.1 Hz, and the modulation at the high frequency was larger for the near target than for the mid and far targets. These characteristics confirm that the horizontal slow phase velocity during yaw OVAR represents a translational otolith-ocular reflex in response to acceleration along the inter-aural axis that is dependent on imagined fixation distance.