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Predictions and declarative memory encoding: two fMRI paradigms provide slim pickings for SLIMM

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

Petar Raykov¹, Kshipra Gurunandan¹, Andrea Greve¹, Richard Henson^1,2; ¹Medical Research Council Cognition and Brain Sciences Unit, University of Cambridge, ²Department of Psychiatry, University of Cambridge

Memory is often better for both highly unexpected and highly expected information. To explain this U-shape relationship between memory and expectancy, the SLIMM framework appeals to two memory systems: one involving the hippocampus and another involving the medial prefrontal cortex (MPFC). Specifically, SLIMM predicts that these two brain regions support opposite ends of the U-shape, with the hippocampus supporting memory for unexpected events, and MPFC underpinning memory for expected events. We tested these predictions in two fMRI paradigms: one examined memory for the location of objects within scenes (e.g., a toothbrush in a bathroom, either on a sink, as expected, or on top of a bin, as not expected); the second tested memory for words that completed well-known idioms either in an expected or unexpected fashion (e.g., “Don’t count your chickens before they… hatch/cook”). Both paradigms replicated the predicted behavioural U-shaped relationship between expectancy and memory performance. However, neither study found the predicted interaction between expectancy and subsequent memory (remembered vs forgotten trials) in terms of fMRI activation in the a priori defined hippocampal and MPFC regions-of-interest. We discuss the implications of these findings for SLIMM, and how our results fit within the broader literature on expectancy and memory.

Topic Area: LONG-TERM MEMORY: Episodic