From the Guidelines
White matter in the brain is primarily composed of myelinated axons, and its development is influenced by both genetic factors and environmental experiences, with proper nutrition playing a crucial role. The process of myelination begins during fetal development and continues through childhood and adolescence, with myelin formed by specialized glial cells called oligodendrocytes in the central nervous system 1. These cells wrap their cell membranes around axons in multiple layers, creating the myelin sheath that appears white due to its high lipid content. The purpose of myelin is to insulate nerve fibers and increase the speed of electrical impulse transmission between neurons. Without myelin, nerve signals would travel much more slowly, affecting brain function.
Some of the key factors that can affect white matter development and function include:
- Genetic factors, such as mutations in the CSF1R gene, which have been linked to primary microgliopathy disrupting the axon-glia integrity 1
- Environmental experiences, such as proper nutrition, particularly iron, fatty acids, and certain vitamins, which play an important role in myelination 1
- Disruptions in myelination, which can lead to various neurological disorders, highlighting the importance of this process for normal brain function and development 1
Recent studies have also highlighted the importance of white matter hyperintensities (WMHs) in cognitive decline, with baseline WMHs increasing the risk of cognitive impairment and dementia across diagnostic categories 1. The location and extent of WMHs, as well as the presence of other risk factors such as Apolipoprotein E (APOE) genotype, can also influence the risk of cognitive decline 1.
Overall, the development and maintenance of white matter is a complex process that is influenced by a range of genetic and environmental factors, and disruptions in this process can have significant consequences for brain function and cognition. Therefore, it is essential to prioritize the health and integrity of white matter through proper nutrition, lifestyle, and management of risk factors.
From the Research
Composition of White Matter
- The white matter is composed of concentrated myelinated axonal fibers extending from neuronal soma and glial cells, such as oligodendrocyte precursor cells (OPCs), oligodendrocytes, astrocytes, and microglia 2.
- Myelinated nerve fibers in the white matter are preserved in alcoholic subjects, suggesting that the loss of white matter is not due to alcohol-induced degeneration of axons in white matter 3.
Factors Affecting White Matter
- Age is a significant factor affecting white matter, with a marked loss of myelinated nerve fibers in the human brain with age, corresponding to a 10% decrease per decade or a total decrease of 45% from the age of 20 to 80 years 4.
- Sex differences also exist in the white matter and myelinated nerve fibers, with males having a larger white matter volume and total length of myelinated fibers than females in young rats, but females having a larger white matter volume and total length of myelinated fibers than males in middle-aged rats 5.
Functions of White Matter
- White matter plays a crucial role in learning, cognition, and psychiatric disorders, with myelination continuing for decades in the human brain and being modifiable by experience 6.
- Myelination affects information processing by regulating the velocity and synchrony of impulse conduction between distant cortical regions, and cell-culture studies have identified molecular mechanisms regulating myelination by electrical activity 6.