Abstract
Saccadic eye movements bring events of interest to the center of the retina, enabling detailed visual analysis. This study explored whether irrelevant auditory (experiments A, B & F), visual (C & D) or tactile signals (E & F) delivered around the onset of a visual target modulates saccade latency. Participants were instructed to execute a quick saccade toward a target stepping left or right from a fixation position. We observed an interaction between auditory beeps or tactile vibrations and the oculomotor reaction that included two components: a warning effect resulting in faster saccades when the signal and the target were presented simultaneously; and a modulation effect with shorter-or longer-latencies when auditory and tactile signals were delivered before-or after-the target onset. Combining both modalities only increased the modulation effect to a limited extent, pointing to a saturation of the multisensory interaction with the motor control. Interestingly, irrelevant visual stimuli (black background or isoluminant noise strips in peripheral vision, flashed for 10 ms) increased saccade latency whether they were presented just before or after target onset. The lack of latency reduction with visual signals suggests that the modulation observed in the auditory and tactile experiments was not related to priming effects but rather to low-level audio- and tactile-visual integration. The increase in saccade latency observed with irrelevant visual stimuli is discussed in relation to saccadic inhibition. Our results demonstrate that signals conveying no information regarding where and when a visual target would appear modulate saccadic reactivity, much like in multisensory temporal binding, but only when these signals come from a different modality.
Highlights
Our environment continuously provides information through physical signals that are transduced and processed by various sensory systems
In order to evaluate the extent of the warning effect when a beep is delivered near target onset, we performed single sample t-tests with the nscores observed in the stimulus onset asynchrony (SOA) = 0 ms condition and with the average nscores across the range of SOAs
Supposing that the same perceptual law applies to the target onset, we propose that for short SOAs the beep and the target were perceived as being simultaneous while for longer SOAs the perceived target is only shifted in time toward the beep
Summary
Our environment continuously provides information through physical signals that are transduced and processed by various sensory systems. The blowing sound would affects the moment when we visually perceive the visual counterpart of the balloon explosion, the latter being shifted in time toward the auditory signal. This could have consequences on the timing of the saccade that would be programmed to bring the retinal image of the event onto the fovea. Similar multisensory latency variations have been reported for SOAs ranging from −30 ms to +120 ms, again modulated by the spatial congruency between the sound and the visual target [20] These multisensory influences have an effect on saccades that could share similar mechanisms and combine with the gap/overlap effect [21].
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