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What are White Matter Tracts?

Mary McMahon
Mary McMahon
Mary McMahon
Mary McMahon

White matter tracts are signaling pathways in the brain made from bundles of white matter, axons coated in layers of myelin. Some of these tracts are laid down during fetal development, while others develop after birth, as people begin to interact with the environment and acquire skills. A brain imaging technique known as diffusion tensor imaging allows researchers to identify white matter tracts, and doctors can use this to compare a patient's brain with known tracts to see if there are abnormalities or unusual features in someone's brain.

These tracts could be thought of as signal cables. The myelin acts as a sheath to increase electrical conductivity, allowing for very rapid transmission of signals along a white matter tract. Some tracts, known as commissual tracts, span the hemispheres of the brain to communicate information between the left and right brain. In imaging, they can be seen snaking across the middle of the brain to create complete connections.

White matter tracts are signaling pathways in the brain.
White matter tracts are signaling pathways in the brain.

Association tracts run between lobes on the same half of the brain. Different lobes may need to be able to communicate information rapidly to make sense of sensory information and cognitive processes. Projection tracts can transmit information from the brain to the rest of the body. They can be extremely long to allow for conduction of signals across great distances.

White matter tracts are made of bundles of axons coated in myelin.
White matter tracts are made of bundles of axons coated in myelin.

Research on the brain demonstrates that in young people, if a white matter tract sustains trauma, the brain may be able to remap itself. It can take over neighboring tracts to find new ways to send the information. The younger people are, the more adaptable their white matter tracts will be, explaining why young children can recover well from head trauma and invasive brain surgery, including surgery to sever the corpus callosum, the structure connecting the two halves of the brain. This surgery may be used in people with severe seizures that do not respond to more conservative treatments.

Special brain imaging techniques are used to identify and compare white matter tracts in the brain.
Special brain imaging techniques are used to identify and compare white matter tracts in the brain.

In older people, it can be more difficult to recover from damage to the white matter tracts. People with brain damage caused by medications, trauma, surgery, tumors, degenerative diseases, and so forth can experience severe cognitive deficits. Deficits may cluster together, depending on the area of the brain involved and the degree of damage. Researchers interested in dementia and cognitive degeneration study white matter tracts to learn more about how key areas of the brain communicate, and what can be done to help people with cognitive deficits.

Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a TheHealthBoard researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

Learn more...
Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a TheHealthBoard researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

Learn more...

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    • White matter tracts are signaling pathways in the brain.
      By: James Steidl
      White matter tracts are signaling pathways in the brain.
    • White matter tracts are made of bundles of axons coated in myelin.
      By: Balint Radu
      White matter tracts are made of bundles of axons coated in myelin.
    • Special brain imaging techniques are used to identify and compare white matter tracts in the brain.
      By: Mikhail Basov
      Special brain imaging techniques are used to identify and compare white matter tracts in the brain.
    • It may be more difficult for older people to recover from damage to the white matter tracts.
      By: chuugo
      It may be more difficult for older people to recover from damage to the white matter tracts.
    • Damage to white matter tracts may occur as a result of brain surgery.
      By: Kot63
      Damage to white matter tracts may occur as a result of brain surgery.
    • Degeneration of the myelin sheath is associated with multiple sclerosis.
      By: joshya
      Degeneration of the myelin sheath is associated with multiple sclerosis.