Diffusion MRI Data Processing, Fibers Tractography and Group Analysis

Diffusion MRI data were corrected for subject motion, eddy current distortions, and susceptibility artefacts due to the magnetic field inhomogeneity using ExploreDTI toolbox [13]. The diffusion data were reconstructed in the MNI space using q-space diffeomorphic reconstruction to obtain the spin distribution function. A diffusion sampling length ratio of 1.25 was used, and the output resolution was 2 mm [14]. A seeding region was placed at whole brain. An ROI was placed in exactly the same location as the rostral ROI and the second ROI was placed in the subgenual part of the cingulum [15,16]. The anisotropy threshold was 0.15. The angular threshold was 30°. The step size was 1 mm. Tracks with length less than 300 mm were discarded. A total of 1,000,000 seeds were placed. Quantitative anisotropy (QA) and generalized fractional anisotropic (GFA) were derived for each participant. The analysis was conducted using publicly available software DSI Studio (http://dsi-studio.labsolver. org). Figure 1 shows the overview of method. Quantitative statistical comparison of anisotropic parameters cingulum was conducted using analysis of variance (ANOVA) (SPSS version 15: SPSS, Chicago, IL, USA).