Pupil-linked arousal signals track the temporal organization of events in memory

David Clewett,Camille Gasser,Lila Davachi

doi:10.1038/s41467-020-17851-9

David Clewett, Camille Gasser + Show 1 more

Open Access

https://doi.org/10.1038/s41467-020-17851-9

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Abstract

Everyday life unfolds continuously, yet we tend to remember past experiences as discrete event sequences or episodes. Although this phenomenon has been well documented, the neuromechanisms that support the transformation of continuous experience into distinct and memorable episodes remain unknown. Here, we show that changes in context, or event boundaries, elicit a burst of autonomic arousal, as indexed by pupil dilation. Event boundaries also lead to the segmentation of adjacent episodes in later memory, evidenced by changes in memory for the temporal duration, order, and perceptual details of recent event sequences. These subjective and objective changes in temporal memory are also related to distinct temporal features of pupil dilations to boundaries as well as to the temporal stability of more prolonged pupil-linked arousal states. Collectively, our findings suggest that pupil measures reflect both stability and change in ongoing mental context representations, which in turn shape the temporal structure of memory.

Highlights

Everyday life unfolds continuously, yet we tend to remember past experiences as discrete event sequences or episodes
Addressing how the brain transforms continuous experience into memorable episodes is foundational to our understanding of learning and memory
We provide evidence that (1) dynamic fluctuations in pupil size are sensitive to the structure of unfolding experiences, and (2) these pupil-linked autonomic arousal changes are in turn related to how those experiences become encoded and represented as discrete memories

Summary

Introduction

Everyday life unfolds continuously, yet we tend to remember past experiences as discrete event sequences or episodes. Event boundaries lead to the segmentation of adjacent episodes in later memory, evidenced by changes in memory for the temporal duration, order, and perceptual details of recent event sequences. When the surrounding context changes, such as entering a new room or being interrupted by a phone call, people tend to perceive an event boundary that defines the end of the current event and the beginning of a new one[7,8] These event boundaries have a significant impact on how we remember experiences later on by promoting more separated memory representations[1,4,5,9,10,11,12,13,14,15,16,17,18]. Emotionally arousing stimuli can enhance local item-context source memory[25,26]

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