Enduring Myth

I saw the movie, “Limitless”, on Saturday night.  One of the characters says something to the effect that it’s common knowledge that we use only 20 percent of our brain.  This piece of information is one of the premises the movie is built on.  It may be understood by most people that we use only a small percentage of the brain; in fact, the widely-circulating myth is that we use only 10 percent of the brain.  Whichever of the two numbers you may subscribe to, the actual truth of the matter is that we use a heck of a lot more than 10 or 20 percent, except perhaps when we are completely relaxed.

According to neurologist, Barry Gordon, at Johns Hopkins School of Medicine in Baltimore, the 10 percent myth is so far off the mark, it’s almost laughable.  Dr. Gordon states that the myth’s durability stems from people’s conceptions about their own brains as they “see their own shortcomings as evidence of untapped gray matter. This is a false assumption. What is correct, however, is that at certain moments in anyone's life, such as when we are simply at rest and thinking, we may be using only 10 percent of our brain.” (1)

Most of the brain is active most of the time.  We use virtually every part of the brain. 

The human brain weighs about three pounds and uses 20 percent of the body's fuel or energy.  Generally speaking, it consists of the cerebrum (also termed the cortex) which is the largest portion, the cerebellum and the brain stem.  The cerebrum performs all higher cognitive functions within its various lobes.  The cerebellum controls motor function.  The brain stem governs involuntary functions like breathing.  Most of the energy used by the brain “powers the rapid firing of millions of neurons communicating with each other. Scientists think it is such neuronal firing and connecting that gives rise to all of the brain's higher functions. The rest of its energy is used for controlling other activities - both unconscious activities, such as heart rate, and conscious ones, such as driving a car.” (2)

At any given time all of the brain’s regions are not concurrently firing:  brain imaging technology has shown this to be the case.  Most regions, however, are continually active over a 24-hour period.

According to John Henley, a neurologist at the Mayo Clinic in Rochester, Minnesota, over the course of a day we use 100 percent of the brain.  While we sleep, areas such as the frontal cortex, which controls things like higher level thinking and self-awareness, or the somatosensory areas, which help people sense their surroundings, are active.

D.

(1) & (2) “Do People Only Use 10 Percent of Their Brains?”, Scientific American Mind, February 2008