FIG. 12.

Simulated configurations of complex fiber bundle architecture at the length scale of a single voxel (61). Note that any tract organization different from a single straight fiber population is typically referred to as “crossing fibers,” including (i) bending (e.g., uncinate fasciculus) and (ii) fanning (e.g., pyramidal projections) fiber bundles. Interdigitating fibers, as shown in (iii), might occur in the region of the centrum semiovale, where the lateral projections of the corpus callosum intersect with the corticospinal tract among others. By contrast, the configuration shown in (iv) reflects adjacent fiber bundles, such as the cingulum bundle and the body of the corpus callosum, which—by definition of the partial volume effect—are captured within a single voxel.