Just as some people seem built to run marathons and have an easier time going for miles without tiring, others are born with a knack for memorizing things, from times tables to trivia facts. These two skills -- running and memorizing -- are not so different as it turns out. Researchers have discovered a single protein that energizes muscles and the brain, which could point to potential treatments in regenerative and developmental medicine as well as ways to address defects in learning and memory, they say.