The findings from the present study, which employed probabilistic tractography as well as resting state fMRI, extend our prior research in several ways. The method and region under investigation was different for our earlier study (13), which used FA extraction from a small portion of the cingulum tract; mean FA was extracted from a circumscribed area, the posterior cingulum, which is proximal to the hippocampus . In this study we employed a probabilistic tractography method that measures connectivity of the entire cingulum, rather than a specific region of this tract, and examined associations between structural and functional connectivity. Unlike our earlier analytic method, probabilistic tractography is sensitive to multi-fiber orientations at the voxel level and individual differences in tract anatomy. Also unlike our earlier studies (10, 13), the present study examined how differences in structure influence function. Consistent with our prior research (10) we found significant effects of PTSD on the cingulum; here, poorer cingulum connectivity was associated with a PTSD diagnosis. In addition, our prior studies (10, 13) used a self-report PTSD measure (PTSD Symptom Scale; (48). Here we
