Mapping Cortical Diffusion Variations with Normal Aging Using DTI: The Validity of the Tensor Interpretation

Aging-related changes in diffusion as measured by diffusion MRI (dMRI) of the white matter (WM) are often interpreted as being driven degeneration of myelinated axons and neurites, but the validity of this tensor (DTI) interpretation of the dMRI signal has never been tested in the cortex. In this study, age-related cortical diffusion variations were assessed using metrics derived from DTI and from the orthogonal-moment diffusion-tensor decomposition (DT-DOME) method. We demonstrate that the tensor interpretation of aging-related dMRI variations are most likely inadequate in the cortex.