Two examples of areas identified by our statistical test (Fig 3D) that contain different pathways in S than in controls, as shown by tractography. To explain why we found statistical differences in fiber orientation, we used tractography to visualize, in S and in controls, the fibers passing through the regions of interest (ROIs) created by the statistical test. Two ROIs are shown here in red (A) and violet (B), transformed into 3D from Fig 3D. Normal fibers in S take a path through the void created by missing SLF fibers. Blue (A) and green (B) fibers are SLF fibers present in controls that were subsequently shown to be absent in S. Instead, other fibers (displayed in white) course through the same areas in S. Note that for clarity, pathways shown are the major pathways passing through the ROIs but do not encompass all fibers through these areas. (A) In controls, the major pathway passing through the ROI (red) is the classical arcuate pathway (blue), while in S, the major pathway through this area connects the parietal and frontal cortices (white). In controls, this parietofrontal pathway is located more medial (not shown in figure). (B) In controls, a part of the SLF connecting temporal to frontal lobes (green) passes through the ROI, while in S, the corticospinal tract (white) is the major pathway passing through here. In controls, the corticospinal pathway is located more medial (not shown in figure). Inset on bottom left in panel A shows superior view of an axial slice with location of ROIs (red and violet) and cysts (cyan-colored). Insets on right panels show diffusion tensor ellipsoids of S and control group within each ROI. Roughly, ellipsoids indicate the probability of diffusion in each direction within that ROI. Note the difference in principal axis direction of these ellipsoids between S and controls. Bars in ellipsoids: green=anterior, blue=superior, red=right.