I am not sure where that myth came from, but I think it has been used by people to indicate that the brain is capable of so much more than it is all ready being used for. Psychic powers, telekinesis, developing the theory of quantum gravity, etc. I never really bought it, either. My understanding is that brain function actually happens on the surface of the brain, and that the folding of the brain's surface is what allows a greater surface area for function.