From Time: Have you ever been so exhausted that you feel basi­cally half-asleep? Turns out, that may be what’s liter­ally going on in your brain, according to a new study published in Nature. In a study of rats, researchers found that when the animals were deprived of sleep, parts of their brains (specif­i­cally, neurons in two areas of the cere­bral cortex) switched into a sleep­like state, even while the rest of the brain stayed awake — and the rats them­selves appeared completely alert. · Go to Does your brain take naps while you’re awake? →