The brain spends energy in rebuilding, rewiring, and renewing itself. According to Dr. Edlund in The Power of Rest, this includes rebuilding the rest of the body. (Remember, everything starts and ends in the brain.) Except for some brief periods of sleep, cells and organs in the body continually communicate with the brain. Yes, this is below your level of consciousness, but it is happening nevertheless. Dr. Marcus Raichle coined the term “default mode,” a label to describe the electrical and blood flow patterns seen when the brain is passively resting. Although a tremendous amount seems to be going on in default mode, scientists don’t quite know what most of it is—at least not yet.