Do theta rhythms in memory formation modulate proactive interference?

Poster Session D - Monday, April 15, 2024, 8:00 – 10:00 am EDT, Sheraton Hall ABC

Alan Peng¹ (alanjc.peng@mail.utoronto.ca), Thomas Biba^1,2, Katherine Duncan¹; ¹University of Toronto, ²Krembil Brain Institute

Computational models (Hasselmo et al., 2002; Ketz et al., 2013) posit hippocampal theta oscillations (3-12Hz) resolve interference between old and new associations by promoting pattern separation or completion at distinct theta phases. Yet it remains untested if our ability to resolve memory interference varies several times per second. Here, we test this prediction using our mnemonic dense sampling approach (Biba et al., 2024), which leverages the finding that attention-grabbing cues can make neural phase predictable across trials. By varying the encoding cue-object delay across milliseconds, we can detect sub-second rhythms in memory formation. During learning, participants classified objects based on the preceding cue color (blue: Indoor/Outdoor; orange: Size), while we varied the cue-object stimulus onset asynchrony (SOA: 300-1200ms in 33ms steps). At retrieval, participants attempted to recall the most recent task associated with each object. We manipulated interference by testing objects after they had been associated with only one task (B: Baseline) or two different tasks (PI: Proactive Interference). For both conditions, we used subsequent memory performance to construct encoding success time-courses across SOAs. Preliminary analyses (n=56 of planned N=100) confirmed worse memory in the PI condition (t=9.02, p<2.3x10-12) and revealed trends toward forming memory rhythmically for both B and PI (6Hz, ps < .05 uncorrected). Spectral analysis also revealed a trend towards individuals oscillating in their susceptibility to proactive interference (B-PI) across SOAs (9 Hz, z=2.42, p=.007, FDR-corrected p=.076). Our present findings suggest proactive interference may vary at the theta frequency, with distinct milliseconds optimized for resolving memory interference.

Topic Area: LONG-TERM MEMORY: Episodic