A New Theory Linking Sleep and Creativity
The two main phases of sleep might work together to boost creative problem-solving.
In 1920, the night before Easter Sunday, Otto Loewi woke up, seemingly possessed of an important idea. He wrote it down on a piece of paper and promptly returned to sleep. When he reawakened, he found that his scribbles were illegible. But fortunately, the next night, the idea returned. It was the design of a simple experiment that eventually proved something Loewi had long hypothesized: Nerve cells communicate by exchanging chemicals, or neurotransmitters. The confirmation of that idea earned him a Nobel Prize in medicine in 1936.
Almost a century later after Loewi’s fateful snoozes, many experiments have shown that sleep promotes creative problem-solving. Now, Penny Lewis from Cardiff University and two of her colleagues have collated and combined those discoveries into a new theory that explains why sleep and creativity are linked. Specifically, their idea explains how the two main phases of sleep—REM and non-REM—work together to help us find unrecognized links between what we already know, and discover out-of-the-box solutions to vexing problems.
As you start to fall asleep, you enter non-REM sleep. That includes a light phase that takes up most of the night, and a period of much heavier slumber called slow-wave sleep, or SWS, when millions of neurons fire simultaneously and strongly, like a cellular Greek chorus. “It’s something you don’t see in a wakeful state at all,” says Lewis. “You’re in a deep physiological state and you’d be unhappy if you were woken up.”
During that state, the brain replays memories. For example, the same neurons that fired when a rat ran through a maze during the day will spontaneously fire while it sleeps at night, in roughly the same order. These reruns help to consolidate and strengthen newly formed memories, integrating them into existing knowledge. But Lewis explains that they also help the brain extract generalities from specifics—an idea that others have also proposed.
“Let’s say you replay memories of birthday parties,” she says. “They all involve presents, cake, and maybe balloons. The areas of the brain that represent those things will be more strongly activated than areas that represent who was at each party, or other idiosyncrasies.” Over time, the details may fade from memory, while the gist remains. “That’s how you might form your representation of what a birthday party is.” (Some scientists have argued that dreaming is the conscious manifestation of this process; it’s effectively your brain watching itself replaying and transforming its own memories.)
This process happens all the time, but Lewis argues that it’s especially strong during SWS because of a tight connection between two parts of the brain. The first—the hippocampus—is a seahorse-shaped region in the middle of the brain that captures memories of events and places. The second—the neocortex—is the outer layer of the brain and, among other things, it’s where memories of facts, ideas, and concepts are stored. Lewis’s idea is that the hippocampus nudges the neocortex into replaying memories that are thematically related—that occur in the same place, or share some other detail. That makes it much easier for the neocortex to pull out common themes.
The other phase of sleep—REM, which stands for rapid eye movement—is very different. That Greek chorus of neurons that sang so synchronously during non-REM sleep descends into a cacophonous din, as various parts of the neocortex become activated, seemingly at random. Meanwhile, a chemical called acetylcholine—the same one that Loewi identified in his sleep-inspired work—floods the brain, disrupting the connection between the hippocampus and the neocortex, and placing both in an especially flexible state, where connections between neurons can be more easily formed, strengthened, or weakened.