Fig 1. Illustration of different underlying fibre architecture in the three measurement regions as found by histology (e.g. [58–61]: Cortico-spinal tract (CST) fibres include those with larger axon diameter and thicker myelin sheaths, which show more parallel arrangements at the level of the posterior limb of internal capsule (PLIC) and more crossing fibres at the level of the centrum semiovale (CS).
On the other hand, the frontal white matter (WM) region also contains crossing fibres, however, with thinner myelin sheaths and lesser axon diameter.