In the structural domain, we tested whether patterns within combined measurements of DMN volume [structural MRI (sMRI)] and axonal fiber bundles [diffusion MRI (dMRI)] would allow the identification of the white matter tracts with the strongest structural association with the DMN. We quantified generalizable patterns in DMN gray matter that inform about microstructural differences of white matter tracts (Johns Hopkins University atlas) across individuals. Gray matter volume was extracted in 32 DMN subregions per participant (Fig. 1) and used for pattern recognition algorithms [maximum-margin support vector regression (SVR)]. This approach could nominate the anatomical fiber tracts that were most predictive of gray matter volume estimates from within the DMN. The target diffusion measures included fractional anisotropy (FA, directional coherence), magnitude of diffusion, axial diffusivity, and radial diffusivity, as well as NODDI parameters, including tract complexity (OD), neurite density (ICVF), and extracellular water diffusion (ISOVF). After accounting for confounds (age, age2, sex, their two-way interactions, head size, and body mass), pattern search models isolated structural associations between DMN and brain-wide anatomical tracts.
