Arousal-based pupil modulation is dictated by luminance

Jasmine Pan,Sam Ling,Michaela Klímová,Joseph T Mcguire

doi:10.1038/s41598-022-05280-1

Abstract

Pupillometry has become a standard measure for assessing arousal state. However, environmental factors such as luminance, a primary dictator of pupillary responses, often vary across studies. To what degree does luminance interact with arousal-driven pupillary changes? Here, we parametrically assessed luminance-driven pupillary responses across a wide-range of luminances, while concurrently manipulating cognitive arousal using auditory math problems of varying difficulty. At the group-level, our results revealed that the modulatory effect of cognitive arousal on pupil size interacts multiplicatively with luminance, with the largest effects occurring at low and mid-luminances. However, at the level of individuals, there were qualitatively distinct individual differences in the modulatory effect of cognitive arousal on luminance-driven pupillary responses. Our findings suggest that pupillometry as a measure for assessing arousal requires more careful consideration: there are ranges of luminance levels that are more ideal in observing pupillary differences between arousal conditions than others.

Highlights

Pupillometry has become a standard measure for assessing arousal state
We replicated previous work finding the modulation of pupil size by math problem difficulty[24,25,26,27,28], wherein the Hard condition produced larger pupil diameters than the Easy condition for all individual luminance levels at the group level (Fig. 4; two-tailed t-test; p < 0.05) as well as larger pupil diameters in the Hard condition compared to the Easy condition when collapsed across luminance levels for all subjects (Supplementary S3; paired t-test t(18) = 9.9118, p < 0.001)
We examined the potential interaction between cognitive arousal and luminance on pupillary responses

Summary

Introduction

Pupillometry has become a standard measure for assessing arousal state. environmental factors such as luminance, a primary dictator of pupillary responses, often vary across studies. The visually-reflexive aspects of pupillometry have been less considered in the vast majority of these studies, as the luminance levels employed, while typically isoluminant within studies, have often varied across studies [e.g., Nassar et al (screen luminance at 0.457 ± 0.010 cd/m2); McGarrigle et al (screen luminance at an intermediate level between 0.0019 cd/m2 and 123 cd/m2 calibrated for each observer)12,13] While these studies all substantiate that pupils dilate with increased levels of arousal, little is known regarding the potential interaction between arousal-driven pupillary changes and the pupillary light reflex. It is unknown whether the modulation of pupil size by arousal differs between environmental conditions of low luminance versus high luminance. There have been a large variety of stimulus and environmental conditions deployed in these studies, all assuming an Scientific Reports | (2022) 12:1390

Objectives

Methods

Results

Conclusion