# Auricular transcutaneous vagus nerve stimulation stabilizes event segmentation through modulation of working memory representations

## TL;DR

A study finds that stimulating the vagus nerve reduces how often people divide experiences into events, suggesting it stabilizes mental representations through GABA effects.

## Contribution

This study provides causal evidence that atVNS modulates event segmentation via GABAergic mechanisms rather than norepinephrine arousal.

## Key findings

- Active atVNS reduced the likelihood of event segmentation compared to sham stimulation.
- Neural decoding accuracy was lower during event boundaries with atVNS, indicating less distinct representations.
- Prefrontal cortex activation decreased with atVNS, supporting a GABAergic inhibitory effect on working memory.

## Abstract

Segmenting continuous experience into discrete units—event segmentation—is fundamental for situational awareness and adaptive action. Based on Event Segmentation Theory, we used auricular transcutaneous vagus nerve stimulation (atVNS) to test whether the control of event segmentation is moderated by norepinephrine and/or GABAergic systems.

Healthy adults (N = 40) completed a double-blind, counterbalanced experiment in which they watched a narrative movie and indicated perceived event boundaries under active atVNS and sham stimulation while the electroencephalogram (EEG) was recorded. Multivariate pattern analysis (MVPA) quantified the decodability of boundary interval (BI) vs no-boundary interval (NBI), and EEG source reconstruction assessed cortical activation.

Relative to sham, active atVNS reduced the likelihood of segmentation. Converging neurophysiological evidence mirrored this behavioral effect: MVPA revealed lower decoding accuracy for BI and NBI, indicating less distinct neural representational patterns. Source reconstruction showed reduced activation in the prefrontal cortex, a region involved in working memory.

Across behavioral and neural measures, atVNS stabilized ongoing event representation and restricted the updating of the current event working model, consistent with a GABAergic modulation of event segmentation. These findings extend prior work linking atVNS to working memory gating and demonstrate its impact on an ecologically relevant cognitive process—event segmentation.

Significance StatementThis study tests whether 2 neuromodulators—norepinephrine (NE) and GABA—causally change how people divide continuous experience into meaningful events—a process called event segmentation. We used auricular vagus nerve stimulation (atVNS) to nudge these systems and compared active stimulation with a sham control. Compared to sham, active atVNS reduced the probability of setting event boundaries. In parallel, the brain activity patterns before the moments of segmenting were less distinct from the no-boundary period than in the sham condition, with lower activity in prefrontal regions. Together, these converging behavioral and neural findings indicate that atVNS stabilizes ongoing event representations and restricts the updating of the current event working model, a pattern that more parsimoniously supports a GABAergic inhibitory gating account over an NE arousal account of event segmentation.

This study tests whether 2 neuromodulators—norepinephrine (NE) and GABA—causally change how people divide continuous experience into meaningful events—a process called event segmentation. We used auricular vagus nerve stimulation (atVNS) to nudge these systems and compared active stimulation with a sham control. Compared to sham, active atVNS reduced the probability of setting event boundaries. In parallel, the brain activity patterns before the moments of segmenting were less distinct from the no-boundary period than in the sham condition, with lower activity in prefrontal regions. Together, these converging behavioral and neural findings indicate that atVNS stabilizes ongoing event representations and restricts the updating of the current event working model, a pattern that more parsimoniously supports a GABAergic inhibitory gating account over an NE arousal account of event segmentation.