Structural and Functional Brain Connectivity Uniquely Contribute to Episodic Memory Performance in Older Adults

Kylie H Alm; Anja Soldan; Corinne Pettigrew; Andreia V Faria; Xirui Hou; Hanzhang Lu; Abhay Moghekar; Susumu Mori; Marilyn Albert; Arnold Bakker

doi:10.3389/fnagi.2022.951076

Structural and Functional Brain Connectivity Uniquely Contribute to Episodic Memory Performance in Older Adults

Front Aging Neurosci. 2022 Jul 12:14:951076. doi: 10.3389/fnagi.2022.951076. eCollection 2022.

Authors

Affiliations

¹ Department of Psychiatry and Behavioral Sciences, Johns Hopkins University School of Medicine, Baltimore, MD, United States.
² Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD, United States.
³ Department of Radiology, Johns Hopkins University School of Medicine, Baltimore, MD, United States.

Abstract

In this study, we examined the independent contributions of structural and functional connectivity markers to individual differences in episodic memory performance in 107 cognitively normal older adults from the BIOCARD study. Structural connectivity, defined by the diffusion tensor imaging (DTI) measure of radial diffusivity (RD), was obtained from two medial temporal lobe white matter tracts: the fornix and hippocampal cingulum, while functional connectivity markers were derived from network-based resting state functional magnetic resonance imaging (rsfMRI) of five large-scale brain networks: the control, default, limbic, dorsal attention, and salience/ventral attention networks. Hierarchical and stepwise linear regression methods were utilized to directly compare the relative contributions of the connectivity modalities to individual variability in a composite delayed episodic memory score, while also accounting for age, sex, cerebrospinal fluid (CSF) biomarkers of amyloid and tau pathology (i.e., Aβ₄₂/Aβ₄₀ and p-tau₁₈₁), and gray matter volumes of the entorhinal cortex and hippocampus. Results revealed that fornix RD, hippocampal cingulum RD, and salience network functional connectivity were each significant independent predictors of memory performance, while CSF markers and gray matter volumes were not. Moreover, in the stepwise model, the addition of sex, fornix RD, hippocampal cingulum RD, and salience network functional connectivity each significantly improved the overall predictive value of the model. These findings demonstrate that both DTI and rsfMRI connectivity measures uniquely contributed to the model and that the combination of structural and functional connectivity markers best accounted for individual variability in episodic memory function in cognitively normal older adults.

Keywords: diffusion tensor imaging; episodic memory; individual differences; multimodal neuroimaging; resting state functional connectivity.

Abstract

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