ATR and Alzheimer disease: AD reflects diffusion parallel to axonal fibers which may reflect axonal injury and RD captures perpendicular diffusion which is linked to demyelination.42 AD values of ATR_L, ATR_R, and ILF_R were inversely correlated with episodic memory, while that of IFOF_R and ILF_R had a negative correlation with MoCA and executive function, respectively.