First, datasets were visually inspected slice-by-slice for each subject. One control was excluded due to severe motion artifact, and 5 participants (1 MJ+ALC and 4 controls) were excluded due to technical problems during scanning (final N=72). Second, datasets were corrected for head motion, eddy current distortion, and signal loss using FSL tools (FMRIB Software Library, Oxford, United Kingdom; (Smith et al., 2004)). Specifically, image acquisitions for each direction were merged into a single 4D file and aligned to the first volume using affine registration with six degrees of freedom and Fourier interpolation to correct for motion (FLIRT-FMRIB's Linear Image Registration Tool; (Jenkinson et al., 2002)). Each of the 15 direction files were then registered to the B0 image using a six-parameter registration in 2D to minimize eddy current distortions (FDT-FMRIB's Diffusion Toolbox 2.0; (Behrens et al., 2003)). Next, phase unwrapping (PRELUDE-Phase Region Expanding Labeler for Unwrapping Discrete Estimates; (Jenkinson, 2003)) and regularization (FUGUE-FMRIB's Utility for Geometrically Unwarping EPIs; (Jenkinson and Smith, 2001)) of field maps were conducted for quantifying field distortions. Resulting measurements were translated into voxel shifts, effectively assigning image intensities to correct voxel locations.
