The refined skull-stripped T1-weighted MRIs were then analyzed by FreeSurfer to measure supratentorial volume, refine the pial surface, and extract the midthickness surface accompanied with T1-weighted and T2-weighted intensities. Each modality was mapped from the volume to the surface space using the HCP approach based on the Connectome Workbench (Version: 1.2.3) (Glasser et al. 2013), i.e., for each vertex of the midthickness surface the average intensity value with respect to a cylinder centered on that vertex was computed. A 14.14 mm Gaussian filter kernel was also applied to those intensity values to extract their low frequency patterns.
