seen as FA increases23. We further observed an increase in free water with aging (Fig 5d); the strongest increase, in the fornix (arrow), is likely due to an increase of the fraction of CSF within voxels spanning this thin tract as it atrophies. Finally, we calculated voxel-wise cross-subject correlation of age with T2 images. This analysis identified peri-ventricular areas, which are most susceptible to white matter hyperintensities known to be associated with aging (Fig 5e).
