Revealing visual working memory operations with pupillometry: Encoding, maintenance, and prioritization

Abstract

Pupillary dynamics reflect effects of distinct and important operations of visual working memory: encoding, maintenance, and prioritization. Here, we review how pupil size predicts memory performance and how it provides novel insights into the mechanisms of each operation. Visual information must first be encoded into working memory with sufficient precision. The depth of this encoding process couples to arousal‐linked baseline pupil size as well as a pupil constriction response before and after stimulus onset, respectively. Subsequently, the encoded information is maintained over time to ensure it is not lost. Pupil dilation reflects the effortful maintenance of information, wherein storing more items is accompanied by larger dilations. Lastly, the most task‐relevant information is prioritized to guide upcoming behavior, which is reflected in yet another dilatory component. Moreover, activated content in memory can be pupillometrically probed directly by tagging visual information with distinct luminance levels. Through this luminance‐tagging mechanism, pupil light responses reveal whether dark or bright items receive more attention during encoding and prioritization. Together, conceptualizing pupil responses as a sum of distinct components over time reveals insights into operations of visual working memory. From this viewpoint, pupillometry is a promising avenue to study the most vital operations through which visual working memory works.This article is categorized under: Psychology > Attention Psychology > Memory Psychology > Theory and Methods

Internal Coupling: Eye Behavior Coupled to Visual Imagery

“…Interestingly, research on the pupillary light response found it to be modulated by covert attention and visuospatial working memory (Binda & Murray, 2015;Hustá et al, 2019;Mathôt & van der Stigchel, 2015;Zokaei et al, 2019), again highlighting the profound connection between attention and eye behavior. The pupil diameter was shown to reflect phases of encoding, maintenance, and prioritization within the visuospatial working memory (Koevoet et al, 2023). This suggests that even the pupillary response is indicative of attentional shifts, whether directed towards external stimuli or internal representations.…”

“…However, pupil size is not a mere reflexive adaptation to the lighting conditions, but increasingly recognized as a read-out of different mental activities. Several lines of research have advocated for the use of pupillometry as a non-invasive tool for measuring cognitive processes, including attention, memory, and visual imagery (for reviews see Koevoet et al, 2023;Mathôt, 2020;Strauch et al, 2022). For example, pupil diameter (PD) is affected by cognitive workload, with increased workload resulting in increased PD, which is an established objective measure of workload demand (for reviews see Beatty & Lucero-Wagoner, 2000;van der Wel & van Steenbergen, 2018 Moreover, visual attention may even interfere with the PLR.…”

Top-down and bottom-up influences on pupil hippus

“…Light induces a discharge of noradrenaline in the LC which increases its activity, leading to a change in pupillary response. Moreover, the differences between the different illumination conditions could correspond to fluctuations in arousal, reflecting the tonic discharge of the locus coeruleus (37). Indeed, bottom-up processing can lead to variations in LC discharge, which acts as a feature-based filter and allows a salient stimulus to enter visual working memory when presented (38).…”

“…In this study, we were able to observe top-down and bottom-up modulations on the pupil over long periods of time. However, it would be interesting to be able to characterise attentional processing using shorter pupil signals (37). This would allow us to study more dynamic aspects of attention orientation and regulation, and thus gain a better understanding of the physiological mechanisms involved in attention modulation of the pupil at rest and during a task.…”