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Cerebral white matter and basal nuclei

The white matter of the hemispheres is located deep to the cortex and consists mostly of neuronal axons. These fibers are coated with a lipid-rich (fatty) substance called myelin that gives them the light color.  The white matter fibers are organized in fasciculi (bundles) that connect the various areas of the nervous system.


There are three main types of fibers depending on the type of areas they connect:

  • Commissural fibers connect different areas between the two cerebral hemispheres.

  • Association fibers connect the different cortical areas within the same cerebral hemisphere.

  • Projection fibers connect the different cortical areas with subcortical structures.

Commissural fibers


right hemisphere