For basic purposes, the cerebral white matter white matter can be classified by location, or by the specific type of white matter tract. Locations include descriptions such as 'periventricular,' 'peri-atrial,' 'subcortical U fiber (in a general sense),' 'centrum semiovale.' White matter in these locations include specific tracts, most of which are challenging to distinguish on routine clinical imaging. These tracts often have complex turning/twisting/fanning morphology, and may be closely juxtaposed and entangled.

The individual tracts can be divided into three general categories: commissural (bridging the two cerebral hemispheres), projection (bridging the cerebral cortex with deep gray structures or the brain stem), and association (bridging cortex) within a single cerebral hemisphere). The basic components and course of direction of major tracts can be depicted on color FA maps from DTI data. On close inspection, some of this same information can be resolved on certain high resolution MRI techniques. The complexity and subtle features are better approximated with advanced tractography techniques (see full classic atlas and scrollable DTI sections for more details).

The primary connection between the cerebral hemispheres is the corpus callosum. Other connections include the anterior commissure, posterior commissure, and interthalamic adhesion.

The corpus callosum is comprised of the rostrum, genus, body, isthmus, and splenium. The tapetum ('carpet of the brain') consists of thin sheets extend from the splenium to cover the lateral wall of the atrium of the lateral ventricles and adjacent ventricular regions. During development, the corpus callosum develops anterior to posterior with the exception of the rostrum, which forms last. In contrast, the corpus callosum is myelinated from posterior to anterior.

-tapetum

MS-undersurface,

Susac's-snowball lesions in central corpus callosum.

Reversible lesion of the splenium of the corpus callosum.

Reference

Sarikcioglu L et al. Tapetum corpus callosi: carpet of the brain. J Hist Neurosci 2007;16(4):432-4

short subcortical U fibers

Long fibers (e.g. cingulum)