Some Things You Can Do In Your Sleep, Literally

By Alison Bruzek

Published September 11, 2014 at 1:32 PM EDT

For those who find themselves sleeping through work — you may one day find yourself working through sleep.

People who are fast asleep can correctly respond to simple verbal instructions, according to a study by researchers in France. They think this may help explain why you might wake if someone calls your name or why your alarm clock is more likely to rouse you than any other noise.

After people learned to sort words while awake, their brains were able to do the same task while asleep.

The connections between sleep, memory and learning aren't new — but the research is notable for its examination of automatic tasks. The study, published Thursday in Current Biology, first recorded the brain waves of people while they were asked to identify spoken words as either animals or objects while they were awake. After each word, the participant used one hand to push a button for animals, and the other hand to push a button for objects.

The brain map produced by the EEG showed where activity was taking place in the brain and what parts of the brain were being prepped for response. This preparation might include hearing the word elephant and then processing that an elephant is an animal. The participants did this until the task became automatic.

The researchers then lulled the participants to sleep, putting them in a dark room in a reclining chair. Researchers watched them fall into the state between light sleep and the deeper sleep known as rapid eye movement (REM). They were then told a new list of words.

This time, their hands didn't move, but their brains showed the same sorting activity as before. "In a way, what's going on is that the rule they learn and practice still is getting applied," Tristan Bekinschtein, one of the authors of the study, told Shots. The human brain continued, when triggered, to respond even through sleep.

But the researchers weren't fully satisfied, so they took it a step further. They did it all again, but instead of animals and objects, they used real words and fake words. They also waited until the participants were more fully asleep.

Again, they found that the sleeping participants showed brain activity that indicated they were processing and preparing to move their hands to correctly indicate either real words or fake words were being spoken.

"It's pretty exciting that it's happening during sleep when we have no idea," Ken Paller, a cognitive neuroscientist at Northwestern University who is unaffiliated with the study, told Shots. "We knew that words could be processed during sleep." But, Paller adds, "we didn't know how much, and so this takes it to, say, the level of preparing an action."

While this sounds like great news for those who could use a few extra hours in the day for memorizing irregular verbs or cramming for the bar exam, the researchers caution that the neural activity they found may apply only to automated tasks. They hope that future studies may look into whether any similar cognitive task begun in an awake state might continue through early sleep — like crunching calculations.

"It's a terrible thought, in the modern world," says Bekinschtein, referring to the pride people take in forgoing sleep for work. "I think, in a way, these experiments are going to empower people ... that we can do things in sleep that are useful."