All anatomical images were processed in the following steps: (1) visual examination for structural abnormalities and artifacts caused by head motion or dental instruments; (2) bias correction to remove MRI inhomogeneities; (3) segmentation into GM, WM, and cerebrospinal fluid (39); (4) registration to the standard Montreal Neurological Institute space included in a linear affine transformation and a non-linear deformation with diffeomorphic anatomical registration through exponentiated lie algebra normalization (40); (5) homogeneity check using covariance between normalized and segmented images; and (6) spatial smoothing with an 8-mm full width at half maximum Gaussian kernel.
