Rebound nystagmus in normal subjects]

Rebound nystagmus represents a disorder of ocular movement in patients with cerebellar lesions. It was reported, however, that it occurred in normal subjects in darkness. Jerk nystagmus, amplitude of 0.5-2 deg and frequency of less than 2Hz, was evoked after prolonged eccentric fixation and fatigue within about 5 to 15 seconds in 7 normal subjects of the experiment. The nystagmus increased depending on the eccentricity and duration of gaze holding. It also depended on the orbital position 10deg left, 0 deg, 10 deg right after eccentric gaze. It is suggested that rebound nystagmus resulted from the leaky neural integrator of the brainstem, and a shift of the null position in the direction of the eccentric gaze. These two components may cause different types of nystagmus by various combinations.