Research and studies conducted by:
Dr. Nolan Altman and Dr. Byron Bernal of the Radiology Department
Beyond the basic division of efferent and afferent fiber tracts, there is a more intricate architecture of the cerebral white matter. In addition ot the long tracts that connect the brain ot the rest of the body, there is a complicated 3D network formed by short connections among different cortical and subcortical regions. The existence of these bundles has been revealed by histochemistry and biological techniques on post-mortem specimens. Brain tracts are not identifiable by direct exam, CT or MRI scans. This difficulty explains the paucity of their description in neuroanatomy atlases and the poor understanding of their functions.
Tractography is a procedure to demonstrate the neural tracts. It utilizes special techniques of magnetic resonance imaging (MRI), and computer post-processing. The resutls are presented in two and 3D images.
The MRI sequences utilized look at the symmetry of brain water diffusion. Bundles of fiber tracts make the water diffuse asymmetrically in a tensor, the major axis parallel to the direction of the fibers. The asymmetry here is called anistropy. There is a direct relationship between the number of fibers and the degree of anistropy.