Eye, head and body movements of the guinea pig in response to optokinetic stimulation and sinusoidal oscillation in yaw.

Reflex head and eye movements were observed in the guinea pig subjected to optokinetic stimulation and whole body oscillation in the yaw axis. Optokinetic stimuli induced low velocity head movements in the direction of the stimulus with stepwise movements in the opposite direction. With motion stimuli, the head was well stabilized in space and moved to new positions in stepwise manner; in the absence of vision the head was not able to maintain a stable position. The onset of a stepwise head movement was always synchronized with a saccadic eye movement in the same direction, the coordination being similar to voluntary movement. During good head stabilization, vestibular-ocular nystagmus did not occur. The guinea pig appears to avoid nystagmus by stabilizing its head preferentially. It is likely that the vestibular ocular reflex compensates for head displacement with unity gain in the frequency range of voluntary and stepwise reflex head movement and that a close relationship exists between the control of saccadic eye movements and that of voluntary or reflex head movement.