White matter is a normal part of the brain, and the brain is divided into white matter and gray matter. Gray matter is generally concentrated in the cerebral cortex, where neuronal bodies are located, and white matter is generally concentrated in the centrum semiovale, basal ganglia, where neuronal axons and myelin sheaths are concentrated, and where the conduction tracts are located. White matter disease, ischemic changes in the white matter, and demyelination of the white matter are often described as a series of imaging changes caused by lesions in the myelin sheath of the white matter or damage to the axons. Since the white matter of the brain is related to nerve conduction, neurological dysfunction can occur when the brain is damaged. Cognitive decline, such as impaired memory, can occur when symptoms are mild, and affective disorders and organic psychiatric disorders can occur when symptoms are more severe.