Why do people sleep? — Well, not just people, but all kinds of animals sleep. When you think about it, it’s actually quite a strange idea that for 1/4 to 1/3 of each day we go unconscious and are oblivious to the world around us. Scientists for years have wondered and studied what goes on when we sleep and why we do it.
Some of the best research happens through serendipity — Matthew Wilson was studying brain activity in rats as they run mazes. One day he accidently left the rats hooked up to the equipment he used to record their brain activity. The rats eventually fell asleep, and to Wilson’s surprise, he found that the brain activity while they were asleep was almost the same as the brain activity when the rats were running the maze.
Learning and consolidating — Wilson started a series of experiments to study this more. And through his experiments he has come up with a theory, not just about rats, but about people too: When you sleep and when you dream you are reworking, or consolidating, your experiences from the day. Specifically you are consolidating new memories and making new associations from the information you processed during the day. Your brain is deciding what to remember and what to let go of, or forget.
Sleep don’t cram — Of course we’ve always heard the advice to “get a good night’s sleep” before a big event, or exam. It turns out that that advice was solid. If you want to remember what you have learned the best thing to do is to go to sleep after you learn and before you need to remember it.
And if you like to read research:
Ji D, Wilson MA (2007). “Coordinated memory replay in the visual cortex and hippocampus during sleep.” Nature Neuroscience 10: 100-7.