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Jasmine Pan, Michaela Klímová, Joseph McGuire, Sam Ling; Luminance dictates arousal-based pupil modulation. Journal of Vision 2021;21(9):2159. doi: https://doi.org/10.1167/jov.21.9.2159.
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© ARVO (1962-2015); The Authors (2016-present)
Pupils constrict and dilate in response to changes in retinal illumination, as well as in response to endogenous factors such as arousal state. However, the interaction between luminance and arousal state on pupillary responses remains relatively unknown. In this study, we sought to examine this interaction by parametrically assessing luminance-driven pupillary responses while concurrently manipulating arousal. To measure the pupillary light response profile, participants viewed a display that varied in luminance. To modulate cognitive arousal, participants concurrently performed a task comprised of auditory math problems, for which cognitive effort was manipulated using Easy (low arousal) and Hard (high arousal) problem sets. Replicating previous work, we found that participants all exhibited nonlinear pupillary light reflexes. To quantify the pupillary light function, and its changes with arousal level, we fit the pupillometry data with a hyperbolic ratio function. At the group-level, our results revealed that the greatest overall modulatory effect of arousal on the pupillary light function occurred at low and mid-luminances—indicating that the modulatory effect of arousal on pupil size multiplicatively interacts with luminance. However, we found that at the level of individual participants, there were qualitatively distinct individual differences in the modulatory effect of arousal on the pupillary light function. These findings have the potential to reshape interpretation of previous pupillometry work, while offering insight and suggestions into the selection of optimal luminances in future pupillometry work.
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