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Sreenivasan Meyyappan, Abhijit Rajan, Harrison Walker, Yuelu Liu, George Mangun, Mingzhou Ding; Cue-evoked pupillary response reveals a left visual field bias in covert spatial visual attention. Journal of Vision 2019;19(10):319a. doi: https://doi.org/10.1167/19.10.319a.
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The right hemisphere plays a dominant role in spatial cognition. Studies have shown that targets appearing in the left visual field are more effectively processed than targets appearing in the right visual field, an effect known as the left visual field bias. It is not known, however, whether such bias exists in covert visual spatial attention in which subjects direct their voluntary attention to either the left or right visual field in anticipation of target processing. We addressed this problem by measuring pupil dilation, a physiological index of effort, from subjects performing a cued visual spatial attention task where they covertly focused their attention to either the left or the right visual field based on an auditory cue. Following a random cue-to-target interval, two rectangular stimuli appeared, one in each visual field, and the subjects reported the orientation of the target in the attended visual field. The following results were found. First, reaction time was faster in the attend-left than attend-right conditions. Second, in response to the auditory cue, the pupils were significantly more dilated while covertly attending to the right visual field compared to the left visual field. Third, the difference in pupil dilation between attend-right and attend-left conditions was correlated with the difference in reaction time between the two conditions. These results (1) support the hypothesis that there is a left visual field bias in covert visual spatial attention (overcoming this bias is effortful and leads to increased pupil dilation) and (2) suggest that the left visual field bias in covert visual spatial attention and that in visual stimulus processing may share common neural substrate.
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