Temporally dissociable engagement of mesolimbic and hippocampal circuits supports memory formation during the resolution of uncertainty

Poster Session B - Sunday, April 14, 2024, 8:00 – 10:00 am EDT, Sheraton Hall ABC

Jia-Hou Poh¹, Abigail Hsiung¹, Scott Huettel¹, R. Alison Adcock¹; ¹Duke University

The engagement of the dopaminergic circuits in anticipation of uncertainty resolving information has been shown to enhance memory formation. However, studies in humans have primarily relied on paradigms where uncertainty is resolved instantaneously by an expected outcome (e.g. trivia), and it is unclear how midbrain activity may be influenced by changing informational states. Here we investigated the interaction between the midbrain and the hippocampus during a line-drawing task where information evolves over time. During fMRI scanning, participants were shown videos of single-line drawings that may (Real) or may not (Scribble) resolve into interpretable objects over 20 secs. Participants made a button press when they had a guess for what the object could be, and when they were certain of the object identity. Videos were divided into an Early and a Late phase, delineated by the button presses. Recognition test conducted 24hrs later showed that participants were more likely to recognize the real videos than the scribbles, and the recognized real videos were associated with greater activation in mesolimbic regions and the hippocampus during the initial viewing. While BOLD activity in the hippocampus and the midbrain were greater for real videos compared to scribbles, this was observed in different phases, whereby hippocampal activation was greater in the Early phase, and midbrain activation was greater in the Late phase. Our findings suggest that activation in the midbrain may reflect the expectation for outcome resolution, and this build up of expectation may be supported by early engagement of the hippocampus during exploration.

Topic Area: LONG-TERM MEMORY: Episodic