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Stefan Van der Stigchel, Tessel Blom, Christiaan Olivers, Sebastiaan Mathot; The pupillary light response reflects encoding, but not maintenance, in visual working memory. Journal of Vision 2016;16(12):363. doi: https://doi.org/10.1167/16.12.363.
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© ARVO (1962-2015); The Authors (2016-present)
Traditionally, the pupillary light response (PLR) has been thought to reflect the amount of light entering the eye. However, recent studies have shown that the PLR is not just a reflexive process, but is also affected by cognitive factors, such as covert visual attention. Given that the PLR appears sensitive to higher order perceptual representations, we examined whether the pupillary light response is modulated by stimuli which are not physically present, but maintained in visual working memory. In all conditions, displays contained both bright and dark stimuli. Participants were instructed to covertly attend and encode either the bright or the dark stimuli, which then had to be maintained in visual working memory for a subsequent change-detection task. As expected, the pupil was smaller when the bright stimuli had to be encoded compared to when the dark stimuli had to be encoded. This indicates that the encoding of information into visual working memory is reflected in the PLR. However, this effect did not sustain during the maintenance phase. This was consistent across all three experiments: whether it was the shape (Experiment 1), orientation (Experiment 2), or luminance (Experiment 3) of the stimulus that was relevant for subsequent behaviour, the maintenance of the stimuli was not reflected in the PLR. A subsequent Bayesian analysis showed that pupil size was likely driven by the brightness of stimuli during encoding, but not maintenance, of visual working memory. We conclude that the content of visual working memory is not reflected in the pupil. Since the pupil has been linked to the focus of visual attention, the results also suggest that attention is not necessary for the maintenance of information in visual working memory.
Meeting abstract presented at VSS 2016
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