Acute stress modulates hippocampal memory and extraction of regularities across experiences

Poster Session E - Monday, April 15, 2024, 2:30 – 4:30 pm EDT, Sheraton Hall ABC

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

Acute stress strongly influences the hippocampus. Most prior research has focused on the encoding of individual events (episodic memory), which is supported by the trisynaptic pathway (TSP; EC-DG-CA3-CA1). Recent studies show that an additional, monosynaptic pathway (MSP; EC-CA1) supports the process of extracting regularities across events (statistical learning). Rodent studies suggest that these pathways are differentially impacted by stress. We investigated this possibility in humans for the first time. Participants were first assigned to a stress group (socially evaluated cold pressor) or a control group (matched warm water) before learning. They then underwent fMRI while encoding sequences of trial-unique scenes containing temporal regularities. Namely, scene categories were arranged into pairs such that some categories (A, predictive) reliably preceded other categories (B, predictable). Participants returned the next day to complete behavioral tests of episodic memory for scene exemplars and statistical learning for category pairs. Initial results suggest that acute stress may enhance statistical learning and bias the hippocampus toward processing predictable information. In the stress group only, the prediction of upcoming B categories could be decoded from BOLD activity patterns in CA2/3/DG during presentation of A items. Behavioral evidence of statistical learning was higher and positively correlated with MSP background connectivity under stress. Stress additionally shifted patterns of episodic encoding during statistical learning, with the stress group showing stronger hippocampal subsequent memory effects for B items. These results reveal a complex impact of stress on human hippocampal processes, enhancing rapid learning of regularities while encouraging active comparison between expectations and inputs.

Topic Area: LONG-TERM MEMORY: Episodic