Morgan Freeman has a new movie. Of course, we can say that just
about every other week. But this one contains an interesting
phrase that has been bounced around popular culture for
more than 80 years. Do we only use 10% of our brain?
Well, I’m an educator and a scientist and I am going to say something shocking – the statement that we only use 10% of our brain is correct – if you know what you’re talking about.
The brain is made up of many kinds of cells - blood vessel cells, neurons of many types, Schwann cells, astrocytes, microglia, satellite cells, and others.
The neurons are the cells that function for “thinking,” they are stimulated by a host of upstream neurons to produce an electrochemical signal (or not to) and they then influence all the neurons with which they come into close contact downstream. Billions of connections sending and receiving neural impulses that somehow come to have meaning when in the right proportions, timing and places.
None of the neurons would work without all these different types neuroglial cells, but the glial cells don’t themselves participate in the neural signaling. The numbers? Neuroglia makes up about 90% of the cell number in the brain. So – we do use about 10% of our brain to send, receive, generate and interpret neural impulses- to think in other words.
What are you saying -this isn’t what Mr. Freeman meant? Oh, he meant that we only use 10% of our neural cells or maybe 10% of their potential function. Well, then he’s utterly wrong. The eponymous character of the current movie is a young lady who is chemically stimulated so that she can use more and more of her brain. Like she wasn’t using much of it already. In fact, the unaltered Scarlett Johansson, and all of us, use 100% of our brain every day.
There's a lot we know about the human brain, and a lot we don’t know. There are portions of the brain that are dedicated, more or less, to specific functions. There is Wernicke’s area for understanding speech, the Pons contain the respiratory centers, and the motor strip is for voluntary movements, just to name a few. However, it’s not like there’s a telekinesis area that we just haven’t booted up yet and is dark on every MRI ever performed. Not every portion of the brain is firing every second, but we do use all parts.
Your inner ear plays a role to, the semicircular canal monitors your head position and sends signal to the brain to keep your head still and upright. You’re breathing – you are breathing, aren’t you? Well, there are myriad inputs and monitoring systems that maintain your breathing rate so all tissues are oxygenated. Your heart rate, your blink, the digestion of that huge burrito you had for lunch – they all require your brain.
You’re using more than 10% of you’re brain just to keep yourself standing there! Are you thinking about that fact? Well then you’re using even more of your brain. If you have a thought - like you’re saying something to yourself, your auditory system responds as if you’re hearing it from outside your body. Many parts of you’re brain are working – and you’re not even trying.
The average brain is only about 2.5-3% of our body mass, but it uses 20% of our energy reserves. Consider the energy needs if we suddenly used the other 90% of our brain. Scarlett probably consumes 1800-2000 calories a day, so her brain scarfs up about 360-400 of those calories. If she started using all her brain – it would require 3600-4000 calories just for itself.
She would have to eat like a Tour de France rider every day just to keep from starving to death. Rule the world? She’ll have to do it from an Old Country Buffet.
So she would have to eat a lot, big deal, right? But remember that our body isn’t that efficient, much of our metabolism is just converted to heat. Our bodies produce about 100 watts of power at our basal metabolic rate – that rate of function which just barely keeps us alive. Converting that to kCal/hr (by online conversion app, it’s not like I know this stuff – I’m a ten percenter at best) shows that the brain would produce about 17.196 kCal/hr.
If Lucy used 100% of her brain, then she would put out 171.96 kCal/hr. This would be enough energy (in Celsius heat units) to raise the temperature of her 3 lb. (1.4 kg) brain by 128˚ C every hour! OK, so not all of it would go to heat, but she would definitely be running about 20˚ C above the normal 37˚ C. Brain damage and death occurs with a fever of about 106 ˚F (41˚ C). Lucy’s brain would be parboiled and served up like an appetizer at one of those fancy gastropubs.
Studies shows that increased mental activity leads to
increased cellular metabolism and increased heat production
in the brain. But don’t try to pick up girls at the pub by saying
you have a fever because you’re so smart.
Believe me, it doesn’t work.
However, the system is complex. Your body has many thermoregulatory functions that would seek then to return the brain to normal temperature. But what if more thinking led to higher core temperature too? That would be great - it would be so easy to pick out the kids for the gifted/talented programs at school – just don’t use a rectal thermometer.
Contributed by Mark E. Lasbury, MS, MSEd, PhD