It's like something out of an old-school Looney Tunes cartoon: a gorilla, sound asleep and snoring in his nest high in a tree, suddenly stands up and takes a few steps. For the gorilla, this would be a very short story with a very bad ending. Humans, on the other hand, sleepwalk all the time. It's a behavior that has fascinated and freaked us out for centuries, from the hand-wringing somnambulism of Lady Macbeth to the strange murder cases involving Ambien-induced sleepwalking.