Funderstanding (a really neat website) defines brain-based learning:
This learning theory is based on the structure and function of the brain. As long as the brain is not prohibited from fulfilling its normal processes, learning will occur.
The key is that the brain isn't prohibited from fulfilling normal processes. Normal processes include breathing, sleeping, having adequate nutrition, and having general health. (How hard is it to think about school if you have a fever or are vomiting?)
In my experience, this is the newest of all theories. I did not study it as an undergrad (I graduated in 2001) but did as a grad student (I graduated in 2008). It is so simple and true.
I think that the cliche "an apple a day" and "you are what you eat" apply to this theory. When students eat junk for breakfast and then heavy, fried starches for lunch, they struggle to think properly. Constipated and thirsty students can't think about math equations or verbals. Sick children without access to health care will struggle. As young children learn so much, so quickly, this theory is why I advocate breastfeeding.
So... this is the start of brain-based learning. As I continue my SAHM life, I will apply brain-based learning to my children (just like I used to do with my students).