Is it true we only use 10% of our brain?
Sigh. They never want to see a derivation of the Nernst equation, or ask about the use of wavelets in fMRI source localization, or want to debate whether the proliferation of pyramidal cell types when calcium binding proteins are used as a classification metric has any real functional significance. Brain and brain. What is brain? This must be how Pete Townshend felt when he tried to play selections from his jazz introspective and the punters in the front row just kept yelling out "Magic Bus! Wooo!"
And then, just to add insult to injury, just when neuroscience is all pfft like I'm so sure gag me, we find out the truth is worse than everyone thought.
Hope springs eternal, as Robert Hooke discovered. The implication being that if we were somehow able to unlock the other 90% of our brains we would all be little Einsteins, or little Mozarts, or little Schopenhauers, or whatever little it is parents pine their children to do these days. Bed Kari Byron, I guess. Not sure how being smarter helps with that, but here we are.
Let's get it out there right off: The answer is no with a but.
It's an impressively stubborn myth, to be sure. Clifford Pickover devotes a chapter in his book Strange Brains and Genius to its origins. Apparently the notion was nourished by a combination of the following:
- The cellular anatomy of the brain, which contains many small neurons that some early anatomists believed were unused or underdeveloped, suggesting a "reserve" of brain exists that could be exploited.
- The gross anatomy of the brain, large portions of which such as the brainstem are not normally under direct conscious control, suggesting a reserve of brain exists that could be exploited.
- Electrophysiology studies which have found only about 10% of the brain is active, suggesting a reserve of brain exists that could be exploited.
- Aging studies which have found you lose about 100,000 neurons per day after age 25 or so, suggesting a reserve of brain exists that could be exploited.
Pickover also lists some pure silliness, such as an off-the-cuff remark made by Einstein seized upon by ESP proponents that appeared to support the 10% notion and their cause. However, even the points listed above with grounding in real biology are not hard to dismiss. Small neurons are just as vital as big 'uns -- most inhibitory neurons are small and they do things like prevent seizures. Lots of things happen in the brainstem that are sorta important -- good luck breathing after repurposing your Botzinger complex to bend spoons. Electrophysiology suggests only about 10% of the brain is active at any given time. The candle of thought Eddie Vedder was looking for to light the name of the elderly woman behind the counter in the small town goes everywhere in the brain, just not all at once. Finally, while it's true normal aging does not necessarily result in catastrophic loss of function, go ask a 90-year-old if they miss their 25-year-old brain. There's a reason academics say their careers end at 30.
Busted, as they used to say on MythBusters (Kari -- call me!). However, just to play devil's advocate, suppose we believe the claim that we only use 10% of our brains. What does that even mean? That 90% of our neurons are sitting idle, like an army of relief pitchers trapped in the bullpen, ready to grant us telepathy and world peace if we could only find the right cocktail of ginko and peyote to get them in the game?
That hypothesis doesn't really jive with the data. After a hundred years of histology we have yet to observe any great pools of disconnected neurons sitting off by their lonesome, refusing to join in the reindeer games. And when people started poking electrodes into the cortex back in the 1950s one of the first things discovered was that neurons along a vertical line from surface to white matter all responded to the same stimulus (light flash, sound beep, skin poke, whatever). If the cell you're recording from ain't responding to a stimulus, it's because you're using the wrong stimulus. That result has held up rather well in the intervening 60 years.
In short, no bullpen. But perhaps that's taking the myth too literally. Perhaps we only use 10% of each neuron, or only 10% of the collective potential processing power of the brain?
That's closer to the realm of possibilities. The brain exhibits a remarkable capacity to recover lost function after insult -- people have survived surgical removal of an entire hemisphere -- suggesting there is indeed much untapped capacity built into it. That being said, 100% recovery is not the norm, and it's unclear what we are to make of such a reorganization anyway. If a company downsizes half its workforce and survives, were the previous employees doing nothing or are those who remain now trying to do twice the work?
The difficulty in assessing such claims is that there is still much we do not understand about normal brain function. If I tell you that 70001 is a prime number and you did not know that beforehand, was the neural circuitry now holding that information previously "unused"? Probably not. Our current understanding of memory is that the substrate is a modification of synaptic connections between neurons. But the neurons existed before the new fact and presumably they were connected to something, if for no other reason that new information must be integrated with existing information to be useful. Isolated facts may help you on Jeopardy but they don't help you escape predators or leave offspring behind.
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Real actual images of LabKitty's brain! |
So the answer to the 10% question is no. A hard-literalist interpretation gets torpedoed by the histology and electrophysiology data and a softer-functional interpretation doesn't really fit with the way new information must be integrated with old. A more-correct interpretation, spouted by amateur neurophysiologists every time this question comes up on Reddit or The View, is that we only use 10% of our brain at one time.
Well, maybe. Have a seat, 'cause I got some bad news.
In a 2003 study (Curr. Biology13:493-497) Peter Lennie of NYU took a detailed look at just how much brain (specifically cortex) could be active at one time based upon ATP energetics (ATP is what neurons crave. It's the dots to their pacman, the Redbull to their little bastards on Xbox Live). His analysis was careful and elegant, and not deserving of the violence yours truly is doing to it presently, but the gist went as follows:
- We (neurowonks) have a good estimate of how much ATP one neuron consumes from studies of rat cortex.
- We have a good estimate of how much larger and how many more neurons there are in the human cortex than rat cortex.
- We have a good estimate of how much glucose (ATP juice) the cortex consumes while humans are doing thinky stuff from functional imaging studies.
Multiplying 1 by 2 and dividing it into 3 (or whatever -- I think you get the idea) Lennie determined the maximum amount of cortex that could be active at any given time. His figure turned out to be a rather depressing 1%.
We don't even rise to the bait of the ole' 10% wives' tale. Even if we could wire up everything to everything else, and made sure none of the bulbs were burned out, and bought miles of extension cord and a mountain of those three-in-one plugs so that everyone could get juice, we still wouldn't win the annual neighborhood Christmas house decoration contest because there's not enough in the checking account to pay the electric bill, to coin a metaphor.
But LabKitty, I hear you object, what if we simply vison quest our way to a more energy-efficient brain!
Well, um, good luck with that. Evolution has been tweaking ATP efficiency for a few hundred million years, so there's prolly not a lot of wiggle room there. And if you're successful, your new thinking cap better come equipped with a heat sink. Because if you start lighting up 100% swathes of cortex, I suspect thermal dissipation is going to become a problem. Might wanna pound some nails into your skull like that guy from HellRaiser. (Please do not pound nails into your skull like that guy from HellRaiser.) Or get a complicated haircut like that guy from House Party. Or one of those ginormous head-fins the king always seems to be wearing in Chinese period dramas. As everyone from Archimedes to Chris Knight has discovered, a buff brain comes at a price.
But, hey, don't let me discourage you from finding your spirit animal. And if you're willing to endure a flaming noggin for Sudoku and spoon bending, then I say you have earned your prize.
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