White matter microstructure in the brain can be assessed with DTI, which measures the diffusion of water molecules in tissue. Common measures of tissue integrity include indices of average diffusion (mean diffusivity; MD), and diffusion isotropy (fractional anisotropy; FA). These measures of white matter integrity reflect numerous aspects of tissue structure, including myelination, axonal integrity and fiber organization (for additional discussion see [32]). Widespread diffusion abnormalities are found among alcohol-exposed individuals (refer to Supplementary Table 4). As an example, reduced FA and increased MD are seen in the splenium and genu of the corpus callosum, respectively [33]. Typically, low FA and high MD are associated with poorer microstructural integrity, however this may not always be the case.
