Temporal characteristics of saccadic eye movements induced by auditory stimuli.

Records of horizontal saccadic eye movements made in response to auditory stimuli in the absence of any target related visual stimuli were obtained from two normal human subjects. A band-limiting derivative filter was convolved with records of eye position to obtain estimates of eye velocity. Eye position and velocity records were analyzed off-line to determine the characteristics of the audio-ocular response (AOR). The latency of the AOR decreased with increasing target movement amplitude. The AOR also exhibited lower peak velocity and longer duration than previously reported visually induced saccades. The time at peak velocity increased as saccade amplitude increased until for eye movements with amplitudes greater than 15 degrees, time at peak velocity showed little further increase. Finally, the AOR displayed a high incidence of dynamic overshoot for abducting movements of the right eye and a low incidence of dynamic overshoot for adducting movements of the right eye. System parameters estimated using system identification techniques indicate that the pulse portion of the active state tension driving the agonist muscle is of lower magnitude for auditory saccades than for visual saccades.