It is pretty well established that exercise can have a huge effect on brain function, specifically through increasing blood flow. Diet will as well, although the mechanisms by which this happens are probably not as well understood.

Actually, now that I think about it, there are a bunch of articles on this. I'm not familiar with the field as much, but I can point you to a free review paper that goes over the topic. http://www.ncbi.nlm.nih.gov/pubmed/22141190