SUMMARY
This article reviewed the literature regarding structural and functional roles of white matter in health and disease. It was found that white matter has a structure consisting of bundles that work to connect areas of gray matter in the brain. These bundles also transmit nerve impulses between neurons. Myelin, the outer coating envelop acts as an insulator and permits the jumping of electrical signals instead of passing through the axon. From a functional point of view, white matter carries the messages among various areas of gray matter through the central nervous system. The white matter is called white due to the presence of the fatty material (myelin) that makes the outer layer of axons, and accelerates the transmission of nerve signals. We showed the impacts of alcohol use and other diseases such as Alzheimer disease on white matter. Taken together, white matter has central roles in health and disease.