This may come as a surprise -- accustomed as you probably are to the idea that nine-tenths of your brain's 100 billion or so neurons are wasting away in Margaritaville. But today's brain researchers, who have much more sophisticated tools than the old electrode-zappers, have discovered that the human brain doesn't seem to have any dormant regions. "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," Johns Hopkins University neurologist Barry Gordon explained to Scientific American in 2008 [source: Boyd].
If you stop to think about it, this shocking revelation is only logical. As science journalist Christopher Wanjek points out in his 2005 book "Bad Medicine," if a human needed only 10 percent of the brain to function, it's unlikely that evolution would have allowed the other 90 percent to develop. The brain, after all, is a glutton for resources. Though it amounts to only five percent of the body's weight, it consumes 20 percent of our supply of oxygen and glucose, and demands a continual supply of both to keep working [source: Wanjek]. Additionally, if a human being only needed 10 percent of his or her brain to function normally, we'd be invulnerable to brain diseases (not to mention head traumas short of decapitation). Instead, as brain researcher Barry J. Beyerstein noted in a 2004 Scientific American article, destroying far less than 90 percent of the brain can have a catastrophic effect, and there doesn't seem to be any portion of the brain that a person can lose without experiencing some sort of loss of function [source: Beyerstein]. Wanjek explains: "A person would be comatose if 90 percent of the brain -- any 90 percent -- were inactive" [source: Wanjek].
It is true that different parts of the brain do different things, and not all at the same time. But while not every single ounce of that three-pound hunk of goo inside your skull is necessarily working at any given moment, brain scans show that over a 24-hour period, pretty much the whole brain gets a workout, and most of the parts are continually active. Even when you're sleeping, regions such as the frontal cortex, which controls higher-level thinking and self-awareness, and the somatosensory areas, which help you to sense your surroundings, remain active [source: Boyd].