white matter


Definition of white matter 

: neural tissue especially of the brain and spinal cord that consists largely of myelinated nerve fibers bundled into tracts, has a whitish color, and typically underlies the cortical gray matter

Examples of white matter in a Sentence

Recent Examples on the Web

In 2014 a study showed that for mice, novel experiences prompt almost immediate changes in white matter—the brain’s connective tissue, or highway system. Susan Pinker, WSJ, "New Skills Build New Brain Architecture, Research Shows," 14 June 2018 When a wild rabbit is in danger, more white matter is needed for faster reflexes and for learning what to be afraid of. Elizabeth Gamillo, Science | AAAS, "Why your pet rabbit is more docile than its wild relative," 25 June 2018 While most business leaders who have spoken out have expressed strong disagreement over the immigration issue, not all view it as a black-and-white matter. Monica Rodriguez, Fortune, "Business Leaders Denounce Family Separations at U.S. Border," 19 June 2018 Eden explains that the image illustrates the white matter pathways in the brain. Lisa Wood Shapiro, WIRED, "The End of Dyslexia," 18 June 2018 After many specialist visits and tests, an MRI found damage to the nerve fibers, or white matter, in her brain. Sumathi Reddy, WSJ, "The ‘Right to Try’ Law Says Yes, the Drug Company Says No," 6 June 2018 Two of these sheets, highly folded, along with their hundreds of millions of wires—the white matter—are crammed into the skull. Christof Koch, Scientific American, "What Is Consciousness?," 8 May 2018 For example, the modeling of a hit in which a player lost consciousness shows that in that collision the corpus callosum oscillated at a higher frequency than the surrounding white matter. Adrian Cho, Science | AAAS, "Concussions originate from ringing deep inside the brain, modeling suggests," 30 Mar. 2018 Older adults with poor fitness levels have more deterioration of white matter in their brains, according to a new study, compared with their fitter peers. Amanda Macmillan, Time, "How Exercise May Help Protect Your Brain From Cognitive Decline and Dementia," 16 Feb. 2018

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'white matter.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of white matter

1674, in the meaning defined above

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Last Updated

4 Oct 2018

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The first known use of white matter was in 1674

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white matter


Medical Definition of white matter 

: neural tissue especially of the brain and spinal cord that consists largely of myelinated nerve fibers bundled into tracts, has a whitish color, and typically underlies the gray matter

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one that holds something together

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