My post is in regard to your symptoms, rather than the concept of burn-out. I often have the same feeling: a feeling of mental dullness and a vague sensation of a fly walking on my head. I haven't seen a specialist about it yet, but in my opinion it is from lack of blood flow to my brain -- a lack of glucose and oxygen and a build-up of the byproducts of metabolism. A drink of water, eating, exercising and deep breathing seems to help, as does meditation or doing an activity that uses a different part of my brain -- something involving feeling and movement rather than reasoning. I know that I tend to have low blood pressure, and I believe that is a factor. I found a book in the library that you might find interesting. It is titled "Preventing Alzheimer's" by William Shankle and Daniel Amen, published in 2004. Good luck.