The brain is still able to process sound and smell when you are asleep
The idea that you can learn in your sleep - perhaps getting to grips with a new language played on a CD while you slumber - is an extremely appealing one, but up until recently there's been no real evidence that it actually works. It's a difficult aspect of learning to test because researchers need to be sure the study participants are truly asleep and that they remain asleep throughout each lesson. Although many studies have shown how important sleep is to consolidating learning, studies looking at whether people can learn vocabulary while asleep have failed to show that it works. But new research from the Weizmann Institute, Israel, indicates that it is possible to learn specific simple behaviours while sleeping, so it could be that only certain types of cognitive processes can be learned during sleep.
Researchers exposed sleeping study participants to a specific tone followed by an odour. They used sounds and odours because both can be utilised without waking the participant, yet scientists know that the brain processes them and responds to them during sleep. The tones were matched with different odours - nice or unpleasant ones - and the process was repeated with the idea that the participants would learn to associate each tone with a particular type of odour. The researchers noted that individuals responded just as they would when they were awake - inhaling deeply when the odour was pleasant, but keeping inhalation brief when it was unpleasant. Then, when the participants were awake, they were exposed to the same tones but without any odours. Although they had no conscious memory of what they had heard and smelled during sleep, the study participants all inhaled deeply when the pleasant-odour tone was played, and briefly when the unpleasant tone odour was played. This indicates that the brain learned to respond to that tone.
Clearly the researchers are some way off from coming up with a way we could learn a new language in our sleep but they're keen to continue exploring their findings. "Now that we know that some kind of sleep learning is possible," says one of the study authors, research student Anat Arzi. "We want to find where the limits lie - what information can be learned during sleep and what information cannot."
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