Do we really only use a portion of our brains?

Anthony L. Komaroff, MD
Internal Medicine
Many parts of the body have some extra capacity built in. You can have an entire lung or kidney removed and get along fine with the one that remains. There's skin, small and large intestine, and bone marrow to spare. If the appendix, thymus, and spleen need to go, so be it. We can do without them if necessary.

But the notion that we use just 10% of our brains, or some other small percentage, isn't true. Brain scans of various kinds have shown we regularly use all of the brain. Some parts are more active at any given time or during a particular activity. Some parts may be less critical for important functions, such as breathing, speaking, understanding, or walking. And the brain is remarkably adaptable, so one part can take over, or compensate, for another. But there is no part of the brain that is known to be unused or completely unnecessary.

I'm not sure where the 10% notion came from, but I do know it gained currency before researchers had a reliable way of measuring brain activity. Even now, MRI and PET scans don't provide a perfect estimate of how much of the brain is being used at any one time. Some redundancy makes sense, but it defies logic and well-accepted scientific principles for an organ to increase in size over the course of thousands of years if 90% of it was going unused—especially considering that the brain requires a good deal of blood flow and energy to keep running.
Dr. Mehmet Oz, MD
Cardiology (Cardiovascular Disease)
Actually, we use all of our brain; we just use different parts at different times. If we didn't need all of our brains, evolution would have made sure to develop smaller ones. But of the 100 billion neurons floating around your neurological galaxy, be assured you're using every one of them.
YOU: The Owner's Manual, Updated and Expanded Edition: An Insider's Guide to the Body that Will Make You Healthier and Younger

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.