The fiber tracking was performed on native, unwarped DTI data for each of the regions of interest separately, using software distributed by Gerig et al. (2005) based on the method of Mori and colleagues (Mori and van Zijl 2002; Xu et al. 2002; Xue et al. 1999). Tracking parameters included white matter extraction threshold (minimum FA) of 0.17, fiber tracking threshold of 0.125, and maximum voxel-to-voxel coherence minimum transition smoothness threshold of 0.80 (∼37° maximum deviation between voxels), with no limit on the number of fibers. The mean FA, λL, and λT of each voxel comprising each fiber, for all fibers, were determined for the left and right cingulate bundles and for the genu and splenium of the corpus callosum.
