Acute stress modulates episodic memory and statistical learning in the hippocampus

Poster Session C - Sunday, March 30, 2025, 5:00 – 7:00 pm EDT, Back Bay Ballroom/Republic Ballroom

Irene Zhou¹ (irene.zhou@yale.edu), Yuye Huang², Zihan Bai¹, Elaine G. Wijaya¹, Lusangelis Ramos¹, Brynn E. Sherman³, Nicholas B. Turk-Browne¹, Elizabeth V. Goldfarb¹; ¹Yale University, ²Johns Hopkins University, ³University of Pennsylvania

Acute stress strongly influences the hippocampus. Prior research has focused on negative stress effects on memory for individual events (episodic memory), which is supported by the trisynaptic pathway (TSP; EC-DG-CA3-CA1). However, an additional, monosynaptic pathway (MSP; EC-CA1) supports the extraction of regularities across events (statistical learning). Based on evidence from rodent studies that these pathways are differentially affected by stress, we hypothesize that stress will facilitate statistical learning (SL). Participants were exposed to acute stress (socially evaluated cold pressor) or a control manipulation before learning. They then underwent fMRI while encoding sequences of unique scenes containing temporal regularities. Namely, scene categories were paired such that some categories (predictive; A) reliably preceded others (predictable; B). The next day, participants completed behavioral tests of episodic memory and SL. As in past work, we successfully decoded prediction of upcoming B categories in CA2/3 in both groups. Consistent with our hypothesis, stress promoted SL and enhanced prediction. With stress (but not control), MSP connectivity predicted better performance on the SL test, which was in turn associated with better episodic memory for predicted exemplars. Predictive items were also represented more categorically in the hippocampus, suggesting anticipation of category-level regularities. In only the control group, retrodiction of A categories during B items could be decoded in CA1, consistent with a bias towards prediction under stress. Together, these results show how stress alters hippocampal circuit mechanisms to prioritize statistical learning and prediction, sometimes at the expense of episodic memory, supporting active comparison between inputs and learned regularities.

Topic Area: LONG-TERM MEMORY: Episodic