EVANSTON, Ill., Nov. 19 (UPI) -- U.S. scientists say they've shown sounds heard during sleep can improve later performance on a memory test, confirming the brain is active during sleep.
The Northwestern University researchers led by Professor Ken Paller and graduate student John Rudoy said they taught 12 study participants to associate 50 images with a random location on a computer screen.
Each image was also associated with a sound; for example, the image of a wine glass was associated with the sound of breaking glass. After learning the location of the objects on the screen, participants slept while scalp electrodes measured their brain activity. During sleep, sounds associated with 25 of the 50 images were softly played.
Upon awakening, participants were asked to recall the location of all 50 images. Although none of the participants reported hearing any sounds during sleep, their recall of locations was more accurate for images cued by sounds they heard during their sleep.
Postdoctoral fellow Joel Voss, one of the study's authors, said: "The study opens avenues for discovering boundaries of what can happen to memories during sleep. Can memories be distorted as well as strengthened? Can people be guided to forget unwanted memories?"
The findings appear in the journal Science.