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Postdoctorial Fellowship Award Winner

Abstract contextual representation in the human mediodorsal thalamus

Poster Session B - Sunday, March 30, 2025, 8:00 – 10:00 am EDT, Back Bay Ballroom/Republic Ballroom

Liu Mengxing1 (mengxing1844@gmail.com), Norman Lam1, Michael Halassa1, Kai Hwang2; 1Tufts University, 2The University of Iowa

Cognitive flexibility—the ability to adapt to changing environments by shifting between different thoughts and action plans, relies on mental representation of the external world (context representation) and tracking context changes. These processes organize the mapping between perceptual inputs and their meanings, yet their neural correlates remain unclear. To address this, we collected behavioral and fMRI data from human subjects performing hierarchical decision-making tasks where the context can abruptly change. Subjects had to adjust their behavior following these abrupt context changes based on feedback. Our data revealed that the BOLD signal pattern in the mediodorsal thalamus (MD) could decode the context, a low-dimensional latent variable representing the relationship between the perceptual cue and the task rule. In contrast, the prefrontal cortex (PFC), the cortical counterpart of the MD, decoded not the latent context but concrete task variables such as the perceptual cue and task rule. To further investigate context change, a hallmark of cognitive flexibility, we developed a Bayesian-based computational model to simulate human behavior during context changes, capturing the context prediction error. When this context prediction error was used as a regressor in the analysis of BOLD signals, general linear model (GLM) identified a cluster in the MD with enhanced activity corresponding to high context prediction error. To our knowledge, this is the first dataset to demonstrate that human MD encodes contextual representations and plays a role in switching across latent cue-to-rule mappings. Our results highlight the critical role of the MD in supporting cognitive flexibility in humans.

Topic Area: THINKING: Decision making

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March 29–April 1  |  2025

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