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Poster Session B: Wednesday, August 13, 1:00 – 4:00 pm, de Brug & E‑Hall

Construction and disruption of hippocampal cognitive graphs in human and machine

Deng Pan¹; ¹University of Oxford

Presenter: Deng Pan

Humans build internal cognitive graphs that encode the structural relationships between states, goals, and concepts, supporting flexible behaviour. Both the hippocampus (HPC) and orbitofrontal cortex (OFC) are implicated in cognitive map formation, but their distinct roles remain debated. We hypothesised that the HC encodes relational structure among states (“state–state” associations), while the OFC links each state to their goals (“state–goal” associations). To test this, participants performed a structure reversal learning task during fMRI, requiring adaptation to changing state transitions and goals. Computational modelling showed that participants utilised abstract structural knowledge for inference, and multivariate analyses revealed complementary neural representations: the HPC represented the transition structures while the OFC encoded goals. A recurrent neural network (RNN) trained via meta-reinforcement learning (meta-RL) recapitulated these patterns. Disrupting the human HPC using transcranial ultrasound stimulation (TUS) or lesioning HPC-like units in the RNN selectively impaired transition structure learning. Together, these results demonstrate complementary roles: the HPC constructs the foundation of cognitive graphs, while the OFC uses them to support goal-directed behaviour.

Topic Area: Reward, Value & Social Decision Making

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