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

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

JOURNAL=Frontiers in Aging Neuroscience

VOLUME=Volume 14 - 2022

YEAR=2022

URL=https://www.frontiersin.org/journals/aging-neuroscience/articles/10.3389/fnagi.2022.951076

DOI=10.3389/fnagi.2022.951076

ISSN=1663-4365

ABSTRACT=Here, 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 (Albert et al., 2014). Structural connectivity defined by diffusion tensor imaging (DTI) measures 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 (Yeo et al., 2011). 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., Aß42/Aß40 and p-tau181), and gray matter volumes of the entorhinal cortex and hippocampus. Results revealed that sex, 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.