Changes in gain of the vestibulo-ocular reflex induced by sinusoidal visual stimulation in goldfish.

The effects of sustained sinusoidal visual stimulation on the vestibulo-ocular reflex (VOR) and the optokinetic reflex (OKR) were investigated. Goldfish were held stationary inside a striped drum rotating sinusoidally about the vertical axis for 3 h. The VOR gain, the ratio of eye to head rotational velocities, was measured in the dark with passive sinusoidal rotation of the fish and showed modest increases that were greatest at the stimulation frequency. Furthermore, the fish generated spontaneous sinusoidal eye movements at approximately the stimulation frequency, and these movements summated with the response to other frequencies of vestibular stimulation in the dark. It is hypothesized that the pathways of OK and VO stimuli converge and that the animal increases gain in a common part when it attempts to stabilize the visual image by increasing its response to the OK signal. Thus increases in gain of both OKR and VOR are produced.