What Is Gray Matter?

Mary McMahon
Mary McMahon

Gray matter or grey matter is a type of neural tissue which is found in the brain and spinal cord. It is named after its distinctive brownish-gray color, in contrast with white matter, another type of neural tissue which appears white because it is coated in myelin sheathes. Many people associate gray matter with intelligence and intellect, because it is a major component in the brain, leading to slang terms like “use those gray cells.”

Gray matter is a major component of the brain.
Gray matter is a major component of the brain.

This type of neural tissue is composed primarily of cell bodies, along with their dendrites. White matter, by contrast, is made from nerve fibers. The purpose is to pass along sensory input, gathering information from the sensory organs and other cells and ensuring that it gets where it needs to go. The speed of communication is determined by the white matter, so one could think of the gray and white matter as the central processing unit of the brain.

High levels of gray matter typically mean high levels of intelligence.
High levels of gray matter typically mean high levels of intelligence.

People associate gray matter with intelligence for a good reason: when a brain is autopsied, it appears to be composed entirely of gray matter. Even before people understood the workings of the body, they recognized that the brain was clearly different, and many surmised that all of those gray cells had to be doing something. This tissue also requires a lot of energy, using about 20% of the body's energy at any given time and taking advantage of a copious blood supply.

Musicians typically have large Broca's Areas, which are composed of gray matter.
Musicians typically have large Broca's Areas, which are composed of gray matter.

Curiously, some ancient cultures notably did not attribute very much importance to the brain. The Egyptians, for example, discarded the brain during preparations for burial, believing it to be largely useless. They believed that intellect and the soul were centered in the heart, and some other cultures had a similar belief.

Imaging studies may be helpful in detecting amounts of gray matter in a human's brain.
Imaging studies may be helpful in detecting amounts of gray matter in a human's brain.

Research on the brain has shown that people have differing amounts of gray matter. The more dense the tissue in a particular region of the brain, the more intelligence or skill the brain's owner is likely to have. People with unusually high levels of intelligence or unique skills tend to have notably high levels of gray matter in the parts of their brains which correlate to their ability. Skilled musicians, for example, have an unusually large Broca's Area.

Incidentally, for those who are wondering why the brain is covered in a network of grooves and ridges, the answer is that these folds increase the surface area of the brain, maximizing the number of neurons which can be packed into this area. The alternative would be to have a massive smooth brain, which would require an absurdly large skull. In addition to looking preposterous, a big skull would be potentially dangerous to the host organism, and extremely impractical during birth.

Gray matter is found in both the brain and spinal cord.
Gray matter is found in both the brain and spinal cord.
Mary McMahon
Mary McMahon

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

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Discussion Comments


Gray matter forms connections within the brain based on need and usage. If, for example, you never learned to talk or walk, the gray matter in those regions of the brain would be diminished as you mature. The brain assimilates skills through repetition and studies, causing the gray matter to form connections within these regions. Gray matter cannot be injected into these areas of the brain to increase capability or capacity. Only in performing the skills can lead to these connections. On the other hand, if skills could be implanted in the brain over time through electromagnetic stimuli at the same wave length as that individual's gray matter, it would allow the skills and knowledge to be assimilated in a retrograde manner, but still requiring practical application of said skills to maintain the skills!

Mind you, we're within the realm of science fiction on this though, according to the majority!


I'm not sure how injecting 'skills' would be bad. You'd only be injecting knowledge/skills that have already been learned. If I wanted a physics injection I'd know as much as the best physicists out there. If the whole world knew as much we'd have rapid advancement of information and social development.

It can't go wrong. It's like saying that we should have never given the public access to schools.


Ever read "Flowers for Algernon"? The scientists in the book tried to manipulate the human brain with tests and a procedure to manually make the man smarter. It had bad effects in the book, but it was fiction. Still, though, it's a costly area to look into. Maybe we need more musicians? Or jugglers. Coordination such as that of jugglers increases the amount of gray matter in a person's brain.


Actually, your body is created with more than enough brain cells, so much in fact, that your brain selectively "prunes" out unessential neurons. This process is driven by practical optimization and allocation of resources.


it would certainly be something to have intelligence manually injected, but even if gray matter could be implanted, those cells wouldn't contain anything inside them, and at least so far, there's no way to put information into those cells.



If people could have intelligence "injected" as you say, what would stop the whole world from getting mental upgrades? Who knows what that would mean for societies on earth, it could result in brilliant and conniving people everywhere causing immense damage. Maybe we should be happy for a "gray matter quota."


It seems to me that some people have a "quota" of gray matter, in that they can have a high count in one area of their brain but lack in another. This would explain the phenomena of brilliant autistic people and eccentric and socially tactless geniuses. They have a high gray matter count in a particular area but lack in social intelligence.


I wonder if gray matter could one day be injected to increase people's overall intelligence. If someone is deficient in a certain area of the brain, perhaps they could increase their gray cell count in that area.

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