Saccadic eye movements in response to visual, auditory, and bisensory stimuli

Saccadic eye movements were recorded and analyzed from eight normal human subjects. Various visual, auditory, and bisensory (visual and auditory) targets were tracked. Primary saccade latency, amplitude, duration, and peak velocity were calculated, as well as overall saccade duration (total time spent making saccades) and final eye position. Saccades made to bisensory targets employing a constant-intensity auditory component were not different from the pure visual target responses. Saccades to bisensory targets having an intermittent auditory component (with sound onset synchronous with the visual component) demonstrated a significant reduction in latency (11.3%) compared to the visual responses. The reduction occurred both for a fixed overhead sound source and for a sound source moving with the visual component. This result indicates that providing an auditory motion or localization cue alone does not reduce latency, but that a sound onset cue facilitates response time. No other response parameters were enhanced by using bisensory targets.