Human Intelligence

Is the brain really gray?
Answered by Cristen Conger, Michael Graham Richard and 1 other
  • Cristen Conger

    Cristen Conger

  • Michael Graham Richard

    Michael Graham Richard

  • Discovery Channel

    Discovery Channel

  1. Cristen Conger Blogger, Stuff Mom Never Told You
    Our circulatory system is swimming with red blood cells and white blood cells, conveniently color-coded nicknames for erythrocytes and leukocytes, respectively. Similarly, our central nervous system splits into gray matter and white matter, delineating between neuron cell bodies and nerve fibers that serve as the body’s information superhighway. And like those handy blood cell handles, referring to gray and white brain regions rolls off the tongue much easier than their proper monikers “substantia grisea” and “substantia alba.”

    To understand how gray matter and white matter are situated in the brain, you can think of the gray matter as a type of protective neurological helmet that sits atop the axon-rich white matter. When you see a human brain, you’re looking at the gray matter that makes up the cerebral cortex. The brain’s telltale topography of curves and crevices – or sulci and gyri in science speak – wiggle their way throughout the gray matter that’s responsible for a host of vital roles including muscle coordination, sensory perceptions, memory and speech. Without the gray matter, we’d be goners in many ways, and not just in terms of basic body functions. In fact, researchers have linked gray matter deficiency to psychological disorders of bipolar disease and schizophrenia as well.

    For something that illuminates and sharpens our daily lives so much, calling this critical brain region “gray” seems somewhat ironic. Could the name instead come from its coloring? After all, the creamy hue of myelin sheaths encasing those precious axons put the “white” in white matter. And iron-fortified hemoglobin makes those red blood cells blush scarlet. Gray matter is in fact ashen, but that doesn’t mean the entire brain is gray. The living brain inside your head -- as opposed to one sitting in a lab -- is highlighted with red, white and even black, from basal ganglia. Just like it’s easier to identify substantia alba simply as white matter, describing the brain as gray is another example of neurological shorthand.

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  2. Michael Graham Richard Writer, TreeHugger
    Most people would assume that the human brain is gray because we often hear references to "gray matter" being the important component of the brain. But in reality, a live human brain is pinkish-beige and has the consistency of soft tofu, according to Dr. Katrina Firlik, a Brain surgeon who wrote about her experiences dealing with this very special organ.

    The pinkish hue is explained by blood, the transport system for nutrients and oxygen. But why isn’t the brain pinkish-gray? That’s because while "gray matter" (which contains neural cell bodies, also called the soma) is in fact gray, most of the volume of the brain is filled with connective "white matter" (axons covered by a white myelin sheath to electrically insulate them). What makes the human brain so powerful is the number of connections between our neurons, which is why it's not surprising to find that so much of our brains are filled up with “wiring” (axons) and not with the actual “CPUs” (neuron cell bodies).

    doctor looking through magnifying glass
    (John Foxx/Getty Images)

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  3. Believe it or not, the brain is mostly gray, even when its owner is alive. That's why we call it gray matter. A preserved brain is always colorless due to the fact that it is floating in a fixative like formaldehyde. However, a living brain does have areas that are red, black or white. The white area is made up of nerve fibers that connect the gray matter. Neuromelanin, a form of black pigment found in the brain, gives a black color to substantia nigra, a substance that is part of the basal ganglia. The red color comes, as you might have guessed, from the numerous blood vessels in the brain.

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