Medial temporal lobe grey and white matter differences in late-life depression: a combined structural and multi-shell diffusion MRI analysis

Motivation: Multi-tissue characterization of structural alterations in late-life depression (LLD) is mainly based on structural MRI and diffusion tensor imaging. Goal(s): To investigate medial temporal lobe (MTL)-related structural alterations using advanced diffusion MRI (dMRI) models and their association with MTL grey matter (GM) volume. Approach: Multi-shell dMRI using constrained spherical deconvolution probabilistic tractography, diffusion kurtosis imaging and fixel-based analysis to investigate alterations in the uncinate fasciculus, cingulum bundle, and fornix. Results: Compared to controls, LLD patients showed differences in multiple dMRI metrics, with lower mean kurtosis in the uncinate fasciculus and fornix being correlated with lower MTL GM volume. Impact: Advanced multi-shell diffusion MRI modelling can identify subtle white matter microstructural differences in late-life depression. Using multimodal MRI to investigate grey and white matter differences holistically in the same population can further our understanding of the neurobiology of psychiatric disorders.