The central nervous system is comprised of many factors, but most important are the brain and spinal cord. White matter makes up parts of the brain and spinal cord and facilitates communication between gray matter and the rest of the body. It can be found in inner layers of the cortex, optic nerves, and central and lower portions of the brain as well as the spinal cord.
White matter is made up primarily of axons of nerve cells and full of myelin, which is a whitish fatty material. It derives its name from its color appearance, which is white when exposed. It works with gray matter, a non-myelinated part of the brain responsible for sending sensory and motor stimulus to the central nervous system to create a response. An analogy of how the two types of matter work together is similar to how a computer’s central processing unit and cables work together. In this analogy, gray matter is the CPU and white matter the cables connecting the CPU to other parts.
Until recently, medical scientists and researchers did not place a great deal of emphasis on white matter. However, as conditions such as dementia and Alzheimer’s became more apparent, it became of interest to researchers. Diseased white matter can impair the central nervous system, just as broken or shorted cables would create problems with a computer network.
One disease that is predominantly associated with white matter is Multiple Sclerosis (MS). The majority of lesions associated with MS occur because of inflammation that causes destruction of the myelin surrounding the axons.
Though much is still unknown about the brain and many neurodegenerative diseases, advances in medical imaging are gradually improving the ability to study white matter and find broken connections and damage or disease these regions of the brain.