Pupil light response reveals the spatial coding of serial order in verbal working memory.

The nature of the mechanisms that allow us to hold temporarily arbitrary sequences of items in memory remain debated. Increasing evidence suggests that serial order is spatially coded in verbal working memory (WM). Verbal items to be remembered would be recoded into spatial tags along a horizontal template. It has been suggested that the first items would be located on the left and the last items on the right. Retrieval would be subtended by spatial attention, and oculomotor mechanisms in particular. Accordingly, eye tracking revealed that the retrieval of first items resulted in leftward eye movements and the retrieval of end items in rightward eye movements. However, the oculomotor system is not a prerequisite to shifting attention. Indeed, the focus of attention can also be shifted covertly (without eye movements). Here, we tracked covert attentional shifts during verbal WM retrieval using the pupil light response. Participants memorized sequences of 5 auditory letters, then indicated whether a probe letter was part of the sequence while fixating the center of a screen whose left and right parts were dark or bright. Covert shifts were measured by pupil dilation in response to luminance differences between the left and right sides of the screen. Results showed that retrieving first items increased pupil dilation when the dark side was on the left, while retrieving end items increased dilation when the dark side was on the right. This suggests that serial order processing in verbal WM involves spatial attentional shifts beyond those responsible for eye movements.

Affiliations

UCLouvainSSH/IPSY - Psychological Sciences Research Institute

Citations

APA
Chicago
FWB

Masson, N., Gerin, S., Geers, L., Lepoittevin, S., & Andres, M. (2025). Pupil light response reveals the spatial coding of serial order in verbal working memory. GDR2025 Vision Forum, Louvain-la-Neuve. https://hdl.handle.net/2078.5/247992