Nice you are in pysch, good luck in you quest, but where I'm from people call me Doc. Man I haven't studied the brain since I graduated, but there are some thing I retained in my long term memory. Just because you have never heard of percentage of brain usage doesn't mean it isn't true. See you do believe in god. Yourself. You're confused , the brain and spinal cord both are made of grey and white matter. The grey matter is the outer cortex which is unmyelinated and under the cortex is the white matter which is all mylelinated nerve tissue. And this is from my long term memory. I have no reason to cite my source, I already know, not believe, know that I'm correct.
If you want to know that's up to you.