2.5.2. Probabilistic tractography
The diffusion parameters per voxel were sampled in DTI space
with the FSL program “bedpostX”. Masks of bilateral nuclei
accumbens, caudate nuclei, and putamen were acquired from the
Harvard-Oxford subcortical atlas in FSL (Fig. 2A). All masks were
automatically registered to participant-specific DTI space, thresholded
at 0.8 to minimalize normalization-related spatial smoothing
and corrected for overlap between masks (Fig. 2B1). The masks
were visually compared with participant-specific high-resolution T1
scans (registered to DTI space) by 2 experimenters and manually
adjusted when necessary (Fig. 2B2).