Diffusion-Weighted MRI Imaging Protocol

As in Hodgetts et al. (2019) (link), scanning was conducted on a GE SIGNA HDx 3T MRI system (General Electric Healthcare, Milwaukee, WI) with an eight-channel receive-only head coil. Whole-brain high angular resolution diffusion imaging data (Tuch et al., 2002 (link)) were acquired using a diffusion-weighted single-shot echo-planar imaging sequence (TE = 89 ms; voxel dimensions = 2.4 × 2.4 × 2.4 mm; FOV = 230 mm × 230 mm; acquisition matrix = 96 × 96; 60 slices aligned AC/PC with 2.4 mm thickness and no gap). Gradients were applied along 30 isotropic directions (Jones et al., 1999 (link)) with b = 1200 s/mm². Three non-diffusion-weighted images were acquired with b = 0 s/mm². Acquisitions were cardiac-gated using a peripheral pulse oximeter. T1-weighted anatomical images were acquired using a three-dimensional fast spoiled gradient-echo sequence (TR/TE = 7.8/3s; voxel dimensions = 1 mm isotropic; FOV ranging from 256 × 256 × 168 mm to 256 × 256 × 180 mm; acquisition matrix ranging from 256 × 256 x 168 to 256 × 256 x 180; flip angle = 20°). These sequences were similar to those used by Hodgetts et al. (2019) (link), with only subtle differences between the two studies (outlined in Supplementary Table 1).