Schilling, Kurt G.; Newton, Allen; Tax, Chantal M. W.; Chamberland, Maxime; Remedios, Samuel W.; Gao, Yurui; Li, Muwei; Chang, Catie; Rheault, Francois; Sepherband, Farshid; Anderson, Adam; Gore, John C.; Landman, Bennett. Scientific Reports 15 (2025): 18396. .听
The white matter in the human brain contains two important structures:听nerve fibers (axons)听that carry signals between brain areas, and听blood vessels听that deliver oxygen and nutrients. Both of these structures are听anisotropic, meaning they are directionally organized and not randomly arranged. Past studies have shown that the direction of these structures can affect how brain scans look, especially with certain types of MRI. However, it’s not well understood how closely the directions of nerve fibers and blood vessels match.听
This study looked at whether these two systems鈥攖he nerve fibers and the blood vessels鈥攖end to run in the same direction in the brain鈥檚 white matter. To do this, researchers scanned healthy young adults using two types of MRI:听diffusion MRI(which maps the direction of nerve fibers) and听susceptibility-weighted imaging听(which shows blood vessels). They then compared the orientation of fibers and vessels in different parts of the brain.听
The results showed that some brain regions had consistent blood vessel directions across individuals. However, in many areas, the blood vessels听did not line up with the main direction of nerve fibers. Still, because brain tissue often contains fibers running in more than one direction (called听crossing fibers), the vessels did line up with听at least one fiber directionin each small region of the brain. In some cases, blood vessels ran in parallel with white matter tracts (bundles of nerve fibers), but听not consistently along the entire length of those tracts, and not for all tracts.听
In summary, the study found that while the layout of blood vessels and nerve fibers in the brain鈥檚 white matter is听related, they are听not perfectly aligned. This insight could help scientists better interpret brain scans and improve our understanding of how the brain is structured, especially when studying neurological diseases.听
听
Fig. 1听
Vascular orientation in individual subjects. For three subjects, SWI images are shown in two orientations showing the full field of view and a zoomed-in region of interest. Overlaid vectors represent the dominant direction of vasculature in each 2听mm region, and are color coded based on orientation, with red, green, and blue representing vasculature oriented in the left/right, anterior/posterior, and superior/inferior directions, respectively. Vasculature is clearly discernable in all imaging views, and orientations visually match the directionality observed in the images.听
