How Does Sleep Affect Consciousness?

It is midnight, and you have finally gotten into bed. But you are so nervous about a job interview in the morning that you are sure you will be awake all night worrying. The next thing you know, the alarm is going off at 7:00 am. Once again, your brain did that mysterious thing, and you fell asleep. What was your brain doing during those 7 hours?

People commonly think that the brain shuts itself down during sleep. In fact, many brain regions are more active when we are asleep than when we are awake. And evidence indicates that some complex thinking, such as working on difficult problems, occurs in the brain even when we are sleeping (Wamsley & Stickgold, 2019). Given that brain activity is the basis for consciousness, how conscious are we during sleep? How does our consciousness change when we dream? To answer these questions, let’s consider how aware we are of the outer world and our mental processes when we sleep.