Sounds can penetrate deep sleep and enhance associated memories upon waking, new research finds.
In a study linking sounds to what is called spatial memory, researchers at Northwestern University in Chicago, US, showed 50 objects on a screen to study participants and played corresponding sounds, like a cat meowing and a tea kettle whistling. Then they played some of the sounds as participants napped.
The participants didn't consciously hear the sounds, but they still did better in tests of remembering where the objects belonged on the screen.
Mind doesn't shut down during sleep
"The research strongly suggests that we don't shut down our minds during deep sleep," said John Rudoy, lead author of the study and a neuroscience post-graduate student, in a news release issued by the university. "Rather this is an important time for consolidating memories."
"While asleep, people might process anything that happened during the day - what they ate for breakfast, television shows they watched, anything," Ken Paller, senior author of the study and professor of psychology at Weinberg College of Arts and Sciences at Northwestern, said in the statement. "But we decided which memories our volunteers would activate, guiding them to rehearse some of the locations they had learned an hour earlier."
The new study adds to the growing research that memories are processed during sleep. And it substantiates past studies showing that the brain is active during sleep, reviewing recently acquired information and integrating it with other knowledge "in a mysterious consolidation process that sustains our memory abilities when awake," the researchers said.
The study findings are published in the journal Science. - (HealthDay News, November 2009)