The eye movement capacity to pursue optokinetic stimuli of increasing frequency and velocity.

Changes in the mean frequency, amplitude and angular velocity of the slow phases of optokinetic nystagmus (OKN) were examined in 72 subjects when the frequency and velocity of optokinetic stimuli were step-wise increased from 1 Hz (17 degrees s-1) up to 12 Hz (204 degrees s-1). The gradual failure of the oculomotor component of visual motion perception was characterized by progressive lagging of the OKN parameters behind the increasing frequency and velocity of moving stimuli and by episodic cessation and reappearance of the OKN pattern at higher frequencies and velocities of stimuli. The frequency and velocity of stimuli at which OKN completely ceased was related to the degree of lagging of the OKN pursuit phases behind the stimuli already at low velocities of their motion.