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Electrophysiological evidence for forward and backward time-based search through episodic memory

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

Roman M. Gutierrez¹, Jeffrey D. Johnson  ; ¹University of Missouri

A critical feature of encoding events into episodic memory is the formation of associations among stimuli as well as with the broader spatial and temporal contexts in which they occur. These associations in turn can then be used to guide strategies at the time of retrieval. Although numerous studies have characterized the neurocognitive processes involved in the associative aspects of episodic memory, a recent research area of interest has focused on how transitions across events and stimuli encoded at different times are handled. Here, our goal was to further understand how search processes during retrieval operate in a forward versus backward manner, with the specific aim to provide novel insights into the neural correlates of such processes. Scalp EEG was acquired from 24 human subjects who completed a series of short encoding-retrieval cycles, with each consisting of a list of about 8 words followed immediately by a directional cued-recall task. In the recall task, subjects were shown an encoded word from a randomly selected list position along with arrows indicating that they should search and report the two words that either came after (forward) or before (backward) the cue in the list. EEG data from 5-second cuing periods was then submitted to multivariate pattern analysis (MVPA) to identify neural activity distinguishing the forward vs. backward conditions. The main results indicated that high-frequency (gamma-band) oscillations play a role in directional recall deliberation and search, suggesting that time-based strategies might serve successful episodic memory retrieval.

Topic Area: LONG-TERM MEMORY: Episodic