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Targeted Memory Reactivation During Sleep Disrupts the Temporal Structure of Episodic Memories

Poster Session E - Monday, March 9, 2026, 2:30 – 4:30 pm PDT, Fairview/Kitsilano Ballroom

Yuqi Zhang¹, Xiaoqing Hu¹; ¹The University of Hong Kong

The temporal structure of episodic memory is both constructive and malleable, dynamically shaped by experience. Notably, emotional salience not only enhances retention but may also disrupt the temporal coherence of memories. Sleep consolidation, through hippocampal-neocortical replay, likely underlies these effects. Using targeted memory reactivation (TMR), we causally tested how sleep reactivation organizes the temporal order of emotional versus neutral episodes. Thirty-eight participants completed a within-subject design. They studied 32 six-image episodes (aversive: neutral-to-negative transition; neutral: all neutral), each paired with distinct auditory cues for the first and second halves. After encoding and baseline affective/temporal tests, closed-loop TMR during N3 sleep reactivated second-half cues for half of the episodes, time-locked to slow-oscillation up-phases. Emotional and temporal memory were reassessed the next morning and one week later. We found that aversive episodes showed higher temporal precision and inflated perceived distances between events relative to neutral episodes; these differences increased after sleep. TMR produced a double dissociation: item recognition improved for both aversive and neutral episodes, while temporal-order accuracy declined. The disruption was segment-specific, limited to cued (second-half) segments and not the early neutral parts, implicating relatively independent processing across episode segments. EEG showed that TMR-evoked theta and sigma power tracked these behavioral effects. Collectively, these results indicate that sleep inflates perceived inter-event distances in aversive episodes. Critically, TMR strengthens item memory but reduces temporal fidelity. Thus, externally driven reactivation during sleep can disrupt the episodic timeline while prioritizing item-level strength.

Topic Area: LONG-TERM MEMORY: Episodic