PRODUCTIVE DREAMS

Scientists found more evidence that we can learn during sleep

It may seem to you like time sleeping is time lost. To our brains, though, sleep is not only productive, but vital. Sleeping provides the chance for our brains to do some chemical house cleaning, which helps us feel rested, awake, and a lot less grumpy the next day.

And now, new research from the Ecole Normale Supérieure in Paris suggests that our brains are capable of both learning and suppressing information during different phases of sleep. Their work was published Aug. 8 in the journal Nature Communications.

Researchers led by Thomas Andrillon, a psychologist studying sleep, hooked up 20 participants to electroencephalograms, which measure the brain’s electrical activity. In the lab before the individuals fell asleep, researches played them white noise, similar to television static. They interspersed this noise with blips of other sounds, and asked participants to pick out when they heard distinct patterns.

Participants were then allowed to get some shuteye through the night while wearing their electroencephalograms (granted, it probably wasn’t the best sleep of their lives). Researchers tracked their phases of sleep by measuring the different patterns of electrical activity the subjects’ brains produced, all while playing them some of the same sound patterns.

The next morning, researchers played participants the white noise interspersed with blips of other sounds again. All of them were better at picking out the patterns played during rapid eye movement, or REM sleep, than they had been the night before. They didn’t remember patterns that were played during non-REM sleep (the light and dreamless sleep that occurs before REM), as well.

Previous work had suggested that our brains can perform some tasks while we sleep. For example, while completing his doctoral research, Andrillon showed that our brains can sort words into basic categories. Additionally, Israeli researchers have shown that it’s possible for us to learn different patterns of smells while sleeping. (For obvious reasons, learning visual information while sleeping is not possible.)

“Not only do we show learning possible, but that the reverse can happen,” Andrillon says. Although he can’t explain why based on their observational data, he thinks that it may be the brain’s way of sorting through and prioritizing important information. “One of the core roles of sleep is to suppress memories so you will maintain the number of memories to a reasonable level,” he says. Our ability to forget, or at least downgrade, inconsequential memories that we form throughout the day may actually make us quicker to recall and analyze the important ones.

Andrillon explained that participants learned an implicit skill—something they could do on their own, but subconsciously. Each person couldn’t tell the researchers how or why they could hear particular pattens better, they just knew it better. Ideally, future studies would look at our ability to learn explicit knowledge—things like new words, mathematical patterns, or even grammar that we can consciously recall—while we sleep.

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