Wiktionary
n. (context neuroanatomy English) A region of the central nervous system containing myelinated nerve fibres and no dendrites
WordNet
n. whitish nervous tissue of the CNS consisting of neurons and their myelin sheaths [syn: substantia alba]
Wikipedia
White matter, named for its relatively light appearance resulting from the lipid content of myelin, refers to axon tracts and commissures.
White matter tissue of the freshly cut brain appears pinkish white to the naked eye because myelin is composed largely of lipid tissue veined with capillaries. Its white color in prepared specimens is due to its usual preservation in formaldehyde.
White matter, long thought to be passive tissue, actively affects how the brain learns and functions. While grey matter is primarily associated with processing and cognition, white matter modulates the distribution of action potentials, acting as a relay and coordinating communication between different brain regions.
Usage examples of "white matter".
I thought it more prudent to make the oracle reply that the operation had failed because the small Count d'Aranda had watched us behind a screen.
No major fractures, probably because of the angle of the stuff he fell on, but there are a series of hairline fractures to the white matter of the spinal column.