HOW MUCH OF THE HUMAN BRAIN IS FOR DIRECT USE IN OUR BODIES AND HOW MUCH IS JUST EXTRA?

The origin of the belief that we use only a small part of our brain is unclear. Perhaps the belief is derived from debates during the early 1800s between those who believed that brain function could be localized to particular regions of the brain and those who believed that the brain acted as a whole. These debates centered around Franz Joseph Gall (1757-1828) and Johann Spurzheim (1776-1832) who developed the field of phrenology: the idea that specific human behaviors and characteristics could be deduced by the pattern and size of bumps on the skull. Not everyone agreed with Gall and Spurzheim. Marie-Jean-Pierre Flourens in the 1700's, an outspoken critic of phrenology, believed that although the cerebral cortex, cerebellum and brainstem had separate functions, each of these areas functioned globally as a whole. Flourens supported his theories with experiments in which he removed areas of the brain (mostly in pigeons) and showed that behavioral deficits increased with size of the ablation. It is possible that over-interpretation and exaggeration of these data led to the belief that only a small portion of the brain is used. American psychologist William James wrote in 1908: “We are making use of only a small part of our possible mental and physical resources.” Albert Einstein and Margaret Mead made similar statements.

What does it mean to “use only 10% of our brains”? Does this statement imply that only 10% of our brain’s neurons are active at any one time? It is important to keep in mind that neurons are not the only type of brain cell. Although there are an estimated 100 billion neurons in the brain there are another ten to fifty times that number of glial cells. Glial cells function to: support the brain structurally, insulate axons, clean up cellular debris around neurons and regulate the chemical composition of the extra-cellular space.

Would we behave normally without 90 billion neurons and billions of glial cells? Would we be just fine if 90% of our brains were removed? In addition to clinical evidence, brain imaging methods appear to refute the 10% brain use statement. For example PET scans show that much of the brain is active during many tasks. Therefore it may appear that some areas of the brain are inactive when in fact they were active but at a lower level compared to other sites. Imagine the brain is a restaurant kitchen. If you looked in on the kitchen at one time, you may see the chef preparing a salad. However you may not know that the main course is cooking in the oven. Certainly there are redundant pathways that serve similar functions. This redundancy may be a type of “safety mechanism” should a pathway for a specific function fail. Still, functional brain imaging studies show that all parts of the brain function—even during sleep. It appears there is no hidden storehouse of untapped brain power. We use all of our brain all of the time. Be happy.