Brain networks predicting variability in episodic memory quality

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Project Summary Episodic memory involves the construction of a complex mental representation that includes key features of an event (i.e., its people, objects, and places) and their relationships with one another. This process has been reliably associated with activity in a core network of posterior medial (PM) brain regions, including areas in medial temporal, medial parietal, and lateral parietal cortex. Yet much remains unknown about how these brain regions contribute to the specificity with which distinct event features are bound and recalled. Past investigations of memory specificity have largely focused on the contributions of individual brain regions, such as the hippocampus and lateral parietal cortex. However, recent evidence suggests that memory specificity may be explained, in part, by functional interactions among brain regions, including those in the PM network. The overarching goal of this proposal is to investigate the brain network interactions predicting the multidimensional quality of episodic memory, focusing on how distinct event features are bound into memory and the specificity with which they are represented. Our central hypothesis is that there are separable pathways through the PM network that maintain the general relational structure and specific details of an event, and that these pathways must interact to embed specific details into event memories. We will test this hypothesis by leveraging the complementary strengths of functional magnetic resonance imaging (fMRI), transcranial magnetic stimulation (TMS), and cognitive experimental design. First, we will examine variability in memory binding and specificity across events, using analytic methods to predict memory quality based on brain network interactions during encoding and retrieval (Aim 1). Second, we will test the causal role of PM network interactions in episodic memory, using a combined TMS and fMRI design to identify post-stimulation network changes and their impact on memory quality (Aim 2). Finally, we will investigate individual differences in episodic memory quality, testing whether they can be explained by differences in PM network recruitment and organization (Aim 3). The proposed research advances a novel framework for understanding the interactive pathways supporting episodic memory, with the potential to significantly transform our understanding of the brain mechanisms supporting memory for complex events. Furthermore, by building a model linking episodic memory quality to specific patterns of network activity and communication, we will be better equipped to understand the mechanisms underlying changes in memory binding and specificity often associated with psychiatric and neurological disorders.