As you recall from high school biology, you're paralyzed while you dream so you don't actually hurt yourself or someone else while you dream of catching the big one or smashing the office copy machine, a la Office Space (see Inception for more). But neurologists are learning more about a condition they call REM sleep behavior disorder, in which the paralysis normally experienced during REM sleep is lost and people actually move around violently. The disorder occurs more often in men, and they've been known to hurt themselves--as well as anyone they happen to be in bed with. Odd, yes. But the real problem is that REM sleep behavior disorder behavior seems to predict the onset of diseases including Parkinson's and Lewy Body dementia by years. In some studies, 80% to 100% of people with REM sleep behavior disorder eventually develop one of these illnesses. Read more about this in Wired Science today, where they includes some interviews with scientists who study the disorder.