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Inducing representational change in the hippocampus through real-time neurofeedback

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Oct 09, 2024 version files 21.93 GB

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Abstract

When you perceive or remember something, other related things come to mind, affecting how these competing items are subsequently perceived and remembered. Such behavioral consequences are believed to result from changes in the overlap of neural representations of these items, especially in the hippocampus. According to multiple theories, hippocampal overlap should increase (integration) when there is high coactivation between cortical representations. However, prior studies used indirect proxies for coactivation, by manipulating stimulus similarity or task demands. Here we induce coactivation in the visual cortex more directly using closed-loop neurofeedback from real-time fMRI. While viewing one object, participants were rewarded for activating the representation of another object as strongly as possible. Across multiple real-time fMRI sessions, they succeeded in using the neurofeedback to induce coactivation. Compared with untrained objects, this coactivation led to memory integration in behavior and the brain: Trained objects became harder for participants to discriminate behaviorally in a categorical perception task and harder to discriminate neurally from patterns of fMRI activity in their hippocampus as a result of losing unique features. These findings demonstrate that neurofeedback can be used to alter and combine memories.