A team at Northwestern University in the US found that memories can be reactivated during sleep and their storage can be strengthened in the process.
In the study, published in journal Nature Neuroscience, participants learned how to play two artificially generated musical tunes with well-timed key presses. Then they took a 90-minute nap, during which the researchers played one of the tunes that had been practiced.
By using EEG methods to record the brain's electrical activity, the team ensured that the soft musical "cues" were presented during slow-wave sleep, a stage of sleep previously linked to cementing memories.
It's found participants made few errors when pressing the keys to produce the melody that had been presented while they slept, compared to the melody not presented.
"Our study extends past research by showing that external stimulation during sleep can influence a complex skill," said senior study author Prof Ken Paller.
James Antony, who led the study, said: "We also found that electrophysiological signals during sleep correlated with the extent to which memory improved. These signals may thus be measuring the brain events that produce memory improvement during sleep."
The age-old myth that you can learn a foreign language while you sleep is sure to come to mind, said study co-author Paul Reber. "The critical difference is that our research shows that memory is strengthened for something you've already learned," he said.
"Rather than learning something new in your sleep, we're talking about enhancing an existing memory by re-activating information recently acquired," he noted.
The study, the researchers hoped, will help them learn more about the basic brain mechanisms that transpire during sleep to help preserve memory storage.
"These same mechanisms may not only allow an abundance of memories to be maintained throughout a lifetime, but they may also allow memory storage to be enriched through the generation of novel connections among memories," Paller said.
