White Matter
Overview
White matter is a component of the central nervous system (CNS) that is primarily composed of myelinated nerve fibers. These fibers, also known as axons, are responsible for the transmission of nerve signals between different parts of the CNS. White matter is named for its relatively light appearance as a result of the lipid content of myelin. In contrast to the gray matter, which is predominantly made up of neuronal cell bodies, white matter contains few neuronal cell bodies and is composed mostly of long-range myelinated axon tracts.
Structure
White matter is found in the deeper tissues of the brain (subcortical), as well as the outer part of the spinal cord. It consists of bundles of myelinated axons, which connect various grey matter areas (the locations of nerve cell bodies) of the brain to each other, and carry nerve impulses between neurons. The myelin sheath, a layer of fat that covers the axon, gives the white matter its color. It also helps to speed up the transmission of signals between neurons.
Function
The main function of white matter is to transmit signals in the form of nerve impulses between different parts of the brain, and between the brain and the spinal cord. This allows for communication between different brain regions, and between the brain and the rest of the body. The speed and efficiency of these signals are greatly increased by the myelin sheath, which acts as an insulator and prevents the electrical signals from dispersing.
Disorders
There are several disorders that can affect white matter, including multiple sclerosis, leukodystrophy, and Alzheimer's disease. These disorders can lead to a variety of symptoms, depending on the areas of the brain that are affected. Symptoms can include problems with movement, balance, vision, and cognition.
Research
Research into white matter has increased significantly in recent years, particularly with the advent of advanced imaging techniques such as diffusion MRI. These techniques have allowed scientists to study the structure and function of white matter in greater detail, and have led to new insights into how white matter changes in response to aging, disease, and injury.