Structural Connectivity of Functionally Defined Episodic Memory Networks: A Large-Scale Connectome-Behavior Study

Previous task-based fMRI work in a large cohort of young adults identified nine large-scale functional brain networks whose encoding-related responsivity was robustly associated with individual differences in episodic memory. It remains unclear whether structural connectivity within these task-fMRI-defined networks explains inter-individual variability in memory performance.

We analyzed diffusion MRI data from 1,156 young adults who completed a picture-free-recall task. For each participant, we reconstructed whole-brain diffusion MRI tractography and extracted within-network connectivity for nine independent components previously defined by task-based fMRI. Edge-wise multiple regression models related within-network connectivity strength to free recall performance, controlling for age and sex. False discovery rate (FDR) correction was applied across all tested edges and networks.

No associations between within-network structural connectivity and memory performance survived FDR correction. Several edges showed nominal (uncorrected) associations with memory, corresponding to very small effect sizes (maximum r < 0.1).

In contrast to previous findings for functional responsivity during encoding, within-network structural connectivity in these functionally defined episodic memory networks is only weakly related to individual differences in memory in young healthy adults.