White Matter in the Brain

Think of the brain as a computer system, and it might be easier to understand. According to the UC Davis Health System, the gray matter (nerve cells) of our brain is the computer and the white matter is the cables that connect everything together and transmit signals.

Want more of a biological explanation? White matter is tissue in the brain composed of nerve fibers. The fibers (called axons) connect nerve cells and are covered by myelin (a type of fat). The myelin is what gives white matter its white color.

Myelin speeds up the signals between the cells, enabling the brain cells to quickly send and receive messages. It also provides insulation for the fibers, preventing the brain from short-circuiting.

White matter makes up about half of the brain, with gray matter making up the other half.

Doctor studying brain scans
 Geri Lavrov Moment/Getty Images

Alzheimer's and White Matter

Some research using imaging studies has found abnormalities in people's white matter prior to the development of Alzheimer's disease symptoms.

Research has also demonstrated the presence of white matter lesions prior to mild cognitive impairment, a condition that carries an increased risk for Alzheimer's disease.

White Matter Hyperintensities

White matter hyperintensities is a term used to describe spots in the brain that show up on magnetic resonance imaging (MRIs) as bright white areas.

According to Charles DeCarli, the director of UC Davis Alzheimer's Disease Center, these areas may indicate some type of injury to the brain, perhaps due to decreased blood flow in that area.

The presence of white matter hyperintensities has been correlated with a higher risk of stroke, which can lead to vascular dementia.

White matter hyperintensities are often referred to as white matter disease.

Initially, white matter disease was thought to simply be related to aging. However, we now know there are other specific risk factors for white matter disease, which include:

  • High blood pressure
  • Smoking
  • Cardiovascular disease
  • High cholesterol. 

While white matter disease has been associated with strokes, cognitive loss, and dementia, it also has some physical and emotional symptoms such as balance problems, falls, depression, and difficulty multitasking (e.g., walking and talking.)

Increasing and Improving White Matter

Some research has found that physical exercise, in particular, cardiorespiratory activities and weight resistance training, was correlated with improved white matter integrity in the brains of those who participated in those studies.

Physical exercise has also been connected to a decreased risk of dementia as well as a slower cognitive decline in people who already have been diagnosed with Alzheimer's or another kind of dementia.

Other research found that when adults learned new skills, the amount of white matter in their brains increased. This was true for learning to read as an adult and learning to juggle.

Additionally, white matter increased relative to the number of hours that professional musicians practiced their instruments.

White matter functioning was also improved by the practice of meditation, and the difference was observed in as little as in two to four weeks.

A Word from Verywell

Historically, science hasn't paid as much attention to our brain's white matter as its gray matter.

We now know, however, how important white matter is to our overall brain health and cognitive ability, as well as how declines in white matter are correlated with impairments in brain functioning.

If you're looking for that small nudge towards a healthier lifestyle, the research about exercise, mental activity, and meditation may help motivate you toward the reward of improved body and brain health. 

7 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. National Institutes of Health, U.S. National Library of Medicine: MedlinePlus. White Matter of the Brain.

  2. Silbert LC, Dodge HH, Perkins LG, et al. Trajectory of white matter hyperintensity burden preceding mild cognitive impairmentNeurology. 2012;79(8):741-747. doi:10.1212/WNL.0b013e3182661f2b

  3. Filley CM. White matter dementiaTher Adv Neurol Disord. 2012;5(5):267-277. doi:10.1177/1756285612454323

  4. University of California Davis Health System, Department of Neurology. White Matter Matters.

  5. Voss MW, Heo S, Prakash RS, et al. The influence of aerobic fitness on cerebral white matter integrity and cognitive function in older adults: results of a one-year exercise intervention. Hum Brain Mapp. 2013;34(11):2972–2985. doi:10.1002/hbm.22119

  6. Svatkova A, Mandl RC, Scheewe TW, Cahn W, Kahn RS, Hulshoff Pol HE. Physical Exercise Keeps the Brain Connected: Biking Increases White Matter Integrity in Patients With Schizophrenia and Healthy Controls. Schizophr Bull. 2015;41(4):869–878. doi:10.1093/schbul/sbv033

  7. Posner MI, Tang Y-Y, Lynch G. Mechanisms of White Matter Change Induced By Meditation TrainingFrontiers in Psychology. 2014;5:1220. doi:10.3389/fpsyg.2014.01220.

Additional Reading

By Esther Heerema, MSW
Esther Heerema, MSW, shares practical tips gained from working with hundreds of people whose lives are touched by Alzheimer's disease and other kinds of dementia.