The audioocular response: intersensory delay.

We reported previously that the latency of saccadic eye movements to auditory stimuli (audioocular response, AOR) was longer than to visual stimuli (Zahn, Abel, & Dell'Osso, 1978). Moreover, unlike the latency to visual stimuli, which increased as a function of the lateral distance of the stimulus from primary posi­ tion, the AOR decreased (i.e., the latency for a stimulus at 10° was longer than one at 20°). The results established that when the head and eyes were fixed at primary position, the latency to a lateral visual stimulus was directly dependent upon the retinal distance of the stimulus with respect to the fovea, whereas the AOR la­ tency was inversely dependent upon the location of the sound with respect to the midline between the ears. In order to define further the interaction of these two spatially disparate systems , the present experiment was designed to separate the retinotopic frame of reference of the visual system from the somatotopic frame of reference of the auditory system by utilizing different initial ocular fixation posi­ tions along the horizontal meridian while the head remained fixed straight ahead. If the saccadic latency to a visual stimulus depends on the distance of the image to the fovea, then there '¥ould be an increase in the latency as a function of the lateral displacement of the retinal image regardless of the starting position of the eye movement. If the saccadic latency to an auditory stimulus is dependent solely on the position of the sound with respect to the head, then there would be longer latencies at the 10° than at the 20° stimulus positions regardless of the starting position of the eye movement. These assumptions were tested in the present experiment.