The human brain is complex. It enables concertos to be composed, manifestos made, and equations solved elegantly. It's also the wellspring of feelings, behaviors, experiences and the repository of memory. So it's no surprise that the brain remains a mystery.
Adding to that mystery is the contention that humans "only" employ 10 percent of their brain. If only regular folk could tap that other 90 percent they too could become savants who remember pi to the 20,000th decimal place or perhaps even a psychic.
Though an alluring idea, the "ten percent myth" is so wrong it is almost laughable, says neurologist Barry Gordon at Johns Hopkins University in Baltimore. While there’s no definitive culprit to the beginning of this legend, the notion has been linked to the American psychologist and author William James, who argued in The Energies of Men that “We are making use of only a small part of our possible mental and physical resources.” It's also been linked to Albert Einstein, who supposedly used it to explain his cosmic intellect.
The myth's durability, Gordon says, stems from people's conceptions about their own brains: their own shortcomings demonstrate the existence of untapped gray matter. This is false. What is correct however, is that at certain moments in anyone's life, such as when we are simply sitting and thinking, we may be using only 10 percent of our brain.
"It turns out though, that we use virtually every part of the brain, and that [most of] the brain is active almost all the time," Gordon adds. "Let's put it this way, the brain represents three percent of the body's weight, and uses 20 percent of the body's energy."
The average human brain weighs about three pounds and is comprised of the hefty cerebrum, which is the largest portion of the brain that performs all higher cognitive functions; the cerebellum, which controls coordination of movement and balance; and the brainstem, which maintains unconscious functions like breathing. The majority of the energy used by the brain powers the rapid firing of neurons communicating with each other. Scientists think it is such neurons firing and connecting to each other that gives rise to all the functions the brain produces. The rest of the brain’s energy is used for controlling other activities, both unconscious activities, such as heart rate, and conscious, such as driving a car.
While it's true that at any given moment all of the brain's regions are not concurrently firing, brain researchers using brain imaging technologies have shown that, like the body's muscles, most are used during a 24-hour period. "Evidence would show over a day you use 100 percent of the brain," says neurologist John Henley at the Mayo Clinic in Rochester, Minn. Even in sleep, areas such as the frontal cortex, which controls things like higher level thinking and self awareness, or the somatasensory areas, which helps people sense their surroundings, are active, Henley explains.
Take the simple act of pouring coffee in the morning. Walking towards the coffeepot, reaching for it, filling the mug with the brew, even leaving extra room for cream, the occipital and parietal lobes, motor-sensory and sensory-motor cortices, basal ganglia, cerebellum, and frontal lobes all activate. A lightning storm of neuron activity occurs almost across the entire brain in the time span of a few seconds.
"This isn't to say that if the brain were damaged that you wouldn't be able to perform daily duties," Henley continues. "There are people who have injured their brains or had parts of it removed who still live fairly normal lives, but that is because the brain has a way of compensating and making sure that what's left, takes over the activity."
Being able to map the brain's various regions and functions is part and parcel of understanding the possible side effects should a region begin to fail. Experts know that neurons that perform similar functions tend to cluster together. For example, neurons that control the thumb's movement are arranged next to those that control the forefinger. Thus, when undertaking brain surgery, neurosurgeons carefully avoid the brains neural clusters related to vision, hearing and movement, enabling the brain to maintain as much of its functions as possible.
What's not understood is how clusters of neurons from the diverse regions of the brain collaborate to form consciousness. So far, there's no evidence that there is one site for consciousness, which leads experts to believe that it is truly a collective neural effort, if not experience. Another mystery hidden within our crinkled cortices is that out of all of the brain's cells, 10 percent are neurons and 90 percent are glial cells, which encapsulate and support neurons and remain largely unknown. Ultimately, it's not that we use 10 percent of our brains, merely that we only understand about 10 percent of how it functions.
