Effect of labyrinthectomy on the dynamic vestibulo-ocular counterrol reflex in the rhesus monkey.

Timeline records of eyeball counterrotation to constant speed rotations about the line of sight were examined in the Rhesus monkey via a linear transformer measurement system using a contact lens. Normal monkeys exhibited a decrease in the amplitude ratio of eye-to-chair motion and an increasing phase lag between eye and chair as the frequency of the motion platform increased. Bilateral labyrinthectomy or prolonged dosage with streptomycin was found to nearly abolish the counterroll reflex. Unilateral damage to the vestibular system resulted in a decrease in the amplitude ratio of the eye-to-chair motion by approximately 50% 1 month after surgery.