MythBusters and the ultimate neuromyth

The myth that you only use 10% of your brain is pervasive, but I never expected to see it on MythBusters. After all, it’s a very – dare I say it? – cerebral myth. I didn’t see much chance for blowing stuff up.

On this week’s episode of MythBusters, it was tested and busted. But I was puzzled by the way they interpreted their results to bust it.

For the second test, they gave Grant and Tori questions while they recorded the brain using magnetoencephalography. (Forgive me if I write that as MEG from here on in.) This is a brain imaging technique that isn’t used as commonly as, say, functional magnetic resonance imaging (fMRI), but as far as I can understand, the logic of how it works is somewhat similar.

In brain imaging studies, brain “activation” is usually the difference between a task where you’re asked to do something, and a control situation where you’re asked to do as little as you can. The important thing is that you’re making a comparison to some baseline activity. And that baseline isn’t zero. I fully admit that I may be misunderstanding this, and MEG may just be that much different than fMRI.

The segment made it sound like we use only about 30% of our brain, rather than 30% of our brain was more active than normal when given these tasks.

It’s like comparing your heart rate during exercise to your resting heart rate. Your resting heart rate isn’t zero, because if it was, you’d be dead.

In some sense, I suppose it doesn’t matter, since the original myth is about how much of our brains we “use” – which is a surprisingly slippery wording. And it’s still good to have information out there that might help make a dent in the undisputed heavyweight champion of neuromyths.

I’m do worry, though, that people will end up thinking that 70% of our brain is just filler. It isn’t.

P.S.—The dramatic tablecloth pull on the same episode also flubbed the explanation of the physics.