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Optimal encoding time windows for memory precision

Poster Session B - Sunday, March 8, 2026, 8:00 – 10:00 am PDT, Fairview/Kitsilano Ballroom

Troy Houser¹ (), Riley Acker¹, Dasa Zeithamova¹; ¹University of Oregon

Are there optimal times for encoding information? Animal research suggests the hippocampus naturally oscillates at a theta rhythm (~4-10 Hz), fluctuating between encoding and retrieval phases. Here, we tested whether theta rhythmicity of memory can be demonstrated using non-invasive behavioral methods in humans. To do so, we combined the mnemonic similarity task with a manipulation of stimulus onset asynchrony (i.e., the duration between a cue and object image) to obtain a behavioral timeseries of memory precision at the group level. Participants encoded a series of images, and were then tested on discriminating encoded images from similar lures. Critically, by timing the image onset at specific delays after a full-screen cue flash, the images putatively appeared at varying phases of the theta cycle, making them easier or harder to encode. Spectral analysis of the accuracy timeseries tested for frequency fluctuations across a range of frequencies (3-14 Hz). Compared to permutation-based null distributions, we found that the ability to precisely encode images fluctuated reliably at frequency of 8 Hz. These findings replicate and extend previous work reporting behavioral evidence of theta rhythmic memory fluctuations in humans and help can pave the way for new lines of inquiry into hippocampal memory traditionally relying on invasive measuments.

Topic Area: LONG-TERM MEMORY: Episodic