Form and accuracy of voluntary ocular tracking movements in response to sinusoidally moving acoustic targets

Form and accuracy of voluntary ocular tracking in response to a horizontal sinusoidally moving auditory stimulus were examined in complete darkness. Forty young, healthy subjects participated in the study. Ocular movements under the applied experimental conditions consisted of a succession of saccades whose direction corresponded to the motion of sound. Though slight intersaccadic drifts were observed, pure smooth pursuit movements could not be recorded. A comparison of the amplitude of sound motion and the corresponding ocular motion showed the latter to be rather inaccurate. Independent of the actual amplitude of the sound motion (+/- 15 degrees up to +/- 90 degrees) the amplitude of the ocular movements, in most cases, remained constant within a range of approximately +/- 35 degrees to +/- 45 degrees. The accuracy in respect to phase relationship between target movement and ocular response was quite good. In response to sinusoidal motion of the sound, the ocular movements usually occurred simultaneously up to 0.5 Hz.