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. 2020 Oct:94:15-23.
doi: 10.1016/j.neurobiolaging.2020.05.001. Epub 2020 May 12.

Free-water metrics in medial temporal lobe white matter tract projections relate to longitudinal cognitive decline

Derek B Archer  1 , Elizabeth E Moore  2 , Niranjana Shashikumar  2 , Logan Dumitrescu  1 , Kimberly R Pechman  2 , Bennett A Landman  3 , Katherine A Gifford  2 , Angela L Jefferson  4 , Timothy J Hohman  1
Affiliations

Free-water metrics in medial temporal lobe white matter tract projections relate to longitudinal cognitive decline

Derek B Archer et al. Neurobiol Aging. 2020 Oct.

Abstract

Although hippocampal volume has served as a long-standing predictor of cognitive decline, diffusion magnetic resonance imaging studies of white matter have shown similar relationships. Still, it remains unclear if gray matter and white matter interact to predict cognitive impairment and longitudinal decline. Here, we investigate whether free-water (FW) and FW-corrected fractional anisotropy (FAT) within medial temporal lobe white matter tracts provides meaningful contribution to cognition and cognitive decline beyond hippocampal volume. Using data from the Vanderbilt Memory & Aging Project (n = 319), we found that FW was associated with baseline memory and executive function beyond that of hippocampal volume and other comorbidities. Longitudinal analyses demonstrated significant interactions of hippocampal volume and inferior longitudinal fasciculus (p = 0.043) and cingulum bundle (p = 0.025) FAT on memory decline and with fornix FAT (p = 0.025) on decline in executive function. Results suggest that FW metrics of white matter have a unique role in cognitive decline and should be included in theoretical models of aging, cerebrovascular disease, and Alzheimer's disease.

Keywords: Cognition; Diffusion MRI; Free-water; Medial temporal lobe; Tractography.

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Conflict of interest statement

Disclosure Statement: No authors report a conflict of interest relevant to this research.

Figures

Figure 1 –
Figure 1 –. Baseline Associations with Composite Memory and Executive Function Performance.
The medial temporal lobe tract measures which were associated with memory (A) and executive function (B) performance include FW in the cingulum bundle, tapetum, uncinate fasciculus (UF), and inferior longitudinal fasciculus (ILF). The association of ILF FW with memory performance (A) and tapetum FW with executive function performance (B) is shown.
Figure 2 –
Figure 2 –. Baseline Tract x Hippocampal Interaction on Annual Change in Memory and Executive Function.
The medial temporal lobe tract measures which had a significant interaction with hippocampal volume for annual change in memory include FAT in the inferior longitudinal fasciculus (ILF) and cingulum bundle (A). For annual change in executive function performance, temporal tract measures which had a significant interaction with hippocampal volume include FAT in the fornix (B). Hippocampal neurodegeneration groups (negative, positive) are based on a previously identified cutoff value for hippocampal neurodegeneration (positive: volume ≤ 6723 mm3) (Mormino et al., 2014).
See this image and copyright information in PMC

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