Illustration of the process by which the altered white matter mask, ROIALT, was generated. Pair-wise (by session) permutation t-tests (50,000 permutations) were conducted for all follow-up sessions (NCA: Retest; FBA: In1, In2, Post) with baseline (NCA: Test; FBA: Pre) to identify voxels exhibiting a statistically-significant change (pFWE < 0.05) at that follow-up session. The resulting sets of voxels for each follow-up session were merged to produce the altered white matter mask. See text (Group-level altered WM mask) for details.