| Popis: |
Progressive age-related changes in white matter morphometry and microstructure have been found throughout the brain. Both declines in white matter (WM) volume and deterioration of microstructural integrity have been observed. Predicting these changes across WM tracts and building an integrated model of age-related WM trajectories has proven challenging. While tractwise differences in volume and microstructural declines are common targets of investigation, there has been relatively little exploration into other attributes of tract morphology or its relation to microstructural measures in vivo. This study seeks to examine ten WM tracts for tract-wise differences in WM volume, length, the ratio of volume to length (VLR), and microstructural integrity as measured by fractional anisotropy (FA) and mean diffusivity (MD) using diffusion MRI data from the Human Connectome Project in Aging (HCP-A). From these measures, we analyzed relationships between morphometry and microstructure in the aging brain with the goal of laying the foundation for a unified model of age-related changes that relates WM microstructure/morphometry and developmental trajectories. Results indicated wide variation in rates and patterns of decline between tracts, as well as tract-specific interactions between tract VLR and microstructure. Robust sex differences were also identified. Our findings demonstrate the need for further exploration of the mechanisms behind both macro- and microstructural differences across the aging brain. |
