Researchers from the Northwestern University have found that memories can be reactivated during sleep, strengthening their storage in the process. And you don't even have to wait for night-time sleep, you can learn even while you take a nap, provided it is of 90 minutes.
In the Northwestern study, research participants learned how to play two artificially generated musical tunes with well-timed key presses. Then while the participants took a 90-minute nap, the researchers presented one of the tunes that had been practiced, but not the other.
"Our results extend prior research by showing that external stimulation during sleep can influence a complex skill," said Ken A. Paller, professor of psychology in the Weinberg College of Arts and Sciences at Northwestern and senior author of the study.
By using EEG methods to record the brain's electrical activity, the researchers ensured that the soft musical "cues" were presented during slow-wave sleep, a stage of sleep previously linked to cementing memories. Participants made fewer errors when pressing the keys to produce the melody that had been presented while they slept, compared to the melody not presented.
"We also found that electrophysiological signals during sleep correlated with the extent to which memory improved," said lead author James Antony of the Interdepartmental Neuroscience Program at Northwestern. "These signals may thus be measuring the brain events that produce memory improvement during sleep."
The findings can be applied to areas other than music—mastering a language, for instance. You can play some sentences of the language you wish to master while you sleep. However, this works in case of things that you've already picked up and not if it's an entirely new skill. "Rather than learning something new in your sleep, we're talking about enhancing an existing memory by re-activating information recently acquired," said Paul J. Reber, associate professor of psychology at Northwestern and a co-author of the study.
The researchers say sleep-based memory processing mechanisms such as these can help a person create permanent memories of things that a person finds important.
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