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Tristan Loria, Joëlle Hajj, Kanji Tanaka, Katsumi Watanabe, Luc Tremblay; The deployment of spatial attention during goal-directed action alters audio-visual integration. Journal of Vision 2019;19(10):111c. doi: https://doi.org/10.1167/19.10.111c.
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The current study examined audio-visual integration processes as a function of spatial attention in the presence or absence of goal-directed aiming. Each trial began with the right index finger on a home position presented on a touch-screen monitor. Three target squares, arranged horizontally, were also displayed. On every trial, one visual flash (F) was presented while the number of auditory beeps (B) varied. The stimuli conditions were 1F (i.e., unimodal), 1F1B (i.e., bimodal congruent), and 1F2B (i.e., bimodal incongruent: fission illusion). These audio-visual cues occurred in the central target square on 70% of the trials, and in the non-target squares on 30% of the trials. After each trial, participants reported the perceived number of flashes. A response was considered correct when the reported number of flashes matched the number of actual flashes presented on that trial. In the no-movement condition, participants kept their finger on the home position for the entire trial. In the movement condition, participants performed a reaching movement to the center target square, with the stimuli presented at movement onset. When initiating a movement, deploying attention to the target’s spatial location was expected to withdraw multisensory processing resources from the non-target locations, thus yielding better perceptual accuracy of the number of flashes at target compared to the non-target locations only for the bimodal stimuli. When unimodal stimuli were presented, perceptual accuracy was worse at the non-target compared to the target locations for both the no-movement and movement conditions. For the bimodal stimuli, perceptual accuracy was worse at the non-target than the target location in the movement condition only. These results indicate that at the onset of a reaching movement, integration of congruent audio-visual cues is reduced at unattended vs. attended spatial locations, whereas integration of incongruent audio-visual cues at unattended locations enhances susceptibility to the fission illusion.
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