Research has debunked the old adage that we use only 10% of our brain and has firmly filed it in the “urban myth” category.

Awake or asleep, whatever we are doing, all parts of our brains are active, although the activity level fluctuates.

Positron emission tomography scans of brain activity in real time are routine, and they show that there are no unused bits.

Neurologists use tiny electrodes to find individual neurons all buzzing busily regardless of activity or lack thereof, not an idle 90%.

Despite detailed investigation with the aid of electroencephalograms; magneto encephalographs; PET scanners; and functional MRI machines, there are as yet no quiet areas to be found.

Autopsies do not find degeneration of all those supposedly atrophied cells.

Brains use more energy per pound than any other parts of our bodies. Brain cells are metabolically expensive to grow, operate and maintain.

The brain, like all our other organs, has been shaped by natural selection. It is against the nature of evolution to squander resources to build and maintain a massively under- utilized organ.

The brain has distinct, localized regions for different kinds of information processing. After decades of research into mapping brain functions onto areas of the brain, we know that all areas serve some function.

Different regions of the brain are highly specialized. Some are more active than others at any given time depending on the situation. All the parts do something, and over time we use all of our brain, just as we use all of our muscles to different degrees at different times.

Studies of the effects of head injury show that there is no area of the brain that can be damaged even a small amount, let alone 90%, by disease, injury or surgery without creating some kind of diminished function, whether it be physical, mental or emotional.

There are some numerical resemblances to the myth, but of a different kind of relationship.

At any given time only 5% to 10% of the neurons are active, otherwise we would be having grand mal seizures, a cranial electrical storm where all neurons are firing.

Only 10% of brain cells are neurons. The other 90% are glial cells, which encapsulate and support neurons. Their function is largely unknown. It could be said then that we understand only about 10% of how the brain functions rather than how much of it functions.

Most of the ATP, the energy molecule produced during low activity, goes toward cell maintenance; the rest powers other brain functions. During activity housekeeping uses about a third of the ATP produced, leaving the rest for other uses.

Some of the ATP supplies the necessary energy to continuously push sodium, calcium and potassium ions through cell membranes to maintain a proper ionic balance inside and outside cells in order to recharge neurons to fire.

The complex equilibrium of unity and diversity of the brain’s functions, coupled with its complex information network, offers a glimmer of hope that someday we will understand its role in consciousness and personality.

Richard Brill is a retired professor of science at Honolulu Community College. His column runs on the first and third Fridays of the month. Email questions and comments to brill@hawaii.edu.