(a) Fiber density in the 3-hinge patterns is higher than other locations of a brain (red color regions). The reconstructed surface is white matter surface. (b) The cross-section shows how dense fibers are projected to a 3-hinge fold. Black arrow heads in (a) and (b) highlight the same 3-hinge fold. Diffusion MRI of this subject was used to produce the streamline fibers (color curves in (b)) and the white matter surface and the fiber density map on this surface in (a). More details are referred to section “Imaging Data Analysis Method”.