The interaction of otolith organ stimulation and smooth pursuit tracking.

The interaction of otolith organ stimulation and horizontal pursuit eye tracking in humans was studied in two different paradigms. In the first we measured the effects of lateral linear acceleration on ocular tracking of a retinal after-image, as compared to eye movements produced by acceleration alone (the linear VOR). The second paradigm determined the improvement in smooth oculomotor tracking presumably due to otolith input, by comparing tracking of an earth-fixed target during subject motion to tracking of target motion with the subject stationary. Subject and target motions in each case were sinusoidal. After-image tracking enhanced the gain of the linear VOR by a factor of 2 to 10. This is interpreted to mean that oculomotor efferent copy information is used to reconstruct an internal representation of target velocity, which is then tracked by the oculomotor system in the after-image condition. In the second paradigm, linear motion information transduced by the otolith organs combined with visual target information to yield improved oculomotor tracking over either system alone.