Pupillometry tracks cognitive load and salience network activity in a working memory functional magnetic resonance imaging task. Issue 2 (8th October 2021)

• Record Type: Journal Article
• Authors: Fietz, Julia; Pöhlchen, Dorothee; Binder, Florian P.; Czisch, Michael; Sämann, Philipp G.; Spoormaker, Victor I.
• Is Part Of: Human brain mapping. Volume 43:Issue 2(2022)
• Page Start: 665
• Page End: 680
• Publication Date: 2021-10-08
• Subjects: cerebral cortex -- gyrus cinguli -- humans -- magnetic resonance imaging -- neuroimaging -- pupil -- short‐term memory; Brain mapping -- Periodicals; 611.81
• DOI: 10.1002/hbm.25678
• Languages: English
• ISSNs: 1065-9471

Abstract

Abstract: The diameter of the human pupil tracks working memory processing and is associated with activity in the frontoparietal network. At the same time, recent neuroimaging research has linked human pupil fluctuations to activity in the salience network. In this combined functional magnetic resonance imaging (fMRI)/pupillometry study, we recorded the pupil size of healthy human participants while they performed a blockwise organized working memory task (N‐back) inside an MRI scanner in order to monitor the pupil fluctuations associated neural activity during working memory processing. We first confirmed that mean pupil size closely followed working memory load. Combining this with fMRI data, we focused on blood oxygen level dependent (BOLD) correlates of mean pupil size modeled onto the task blocks as a parametric modulation. Interrogating this modulated task regressor, we were able to retrieve the frontoparietal network. Next, to fully exploit the within‐block dynamics, we divided the blocks into 1 s time bins and filled these with corresponding pupil change values (first‐order derivative of pupil size). We found that pupil change within N‐back blocks was positively correlated with BOLD amplitudes in the areas of the salience network (namely bilateral insula, and anterior cingulate cortex). Taken together, fMRI with simultaneous measurement of pupil parameters constitutes a valuable tool to dissect working memory subprocesses related to both working memory load and salience of the presented stimuli. Abstract : The present report is a combined functional magnetic resonance imaging/pupillometry study investigating neural correlates of pupil fluctuations during working memory processing. We showed that pupil size between task conditions with varying working memory load correlates with the frontoparietal network and pupil change within conditions correlates with the salience network. This combined setup allows for a differentiation between working memory subprocesses related to cognitive load and salience of the presented stimuli.