For time-starved Americans, few ideas are more appealing than that of learning while sleeping. Why simply doze for eight hours when you can be learning Spanish as well?
The problem, of course, is science, which discredited the idea back in the 1950s. While tapes and CDs for prospective sleep learners are available online, studies have shown that they won't be very effective.
"The research at the time said the only thing that it did was to keep you awake," explained James McGaugh, a professor of neurobiology and behavior at the University of California, Irvine.
But for those who want to get something done while recharging their batteries, a new study suggests you may be able to accomplish something while asleep.
"Our memory systems are still active while we're asleep. Memories can be strengthened while we're asleep," said John Rudoy, a doctoral student in neuroscience at Northwestern and author of a new study appearing in the journal Science.
For the study, individuals were shown 50 objects on a computer screen and asked to remember the location. As they were shown the objects were accompanied by a related sound (for example a "meow" sound with a cat picture). They were tested on their memory and then took a nap. Half of the sounds were played while subjects napped, with their brain activity monitored.
Upon awakening, those subjects were better able to match locations of the objects whose sounds they had heard while asleep. They performed only 3 percent worse than they had on the first test with objects they heard a sound for, while they performed 18 percent worse in trying to match the location of objects whose sound they did not hear.
That effect did not occur in a different set of subjects who did the same test but did not nap, instead hearing the sounds played while still awake.
Rudoy explained that while the research suggests strengthening memories, don't count on being able to learn calculus while catching Zs.
"We show that you can strengthen existing memories while you sleep, but you can't learn new things while you sleep," he said.
Since the researchers did not look at linguistic cues, the research does not mean you can benefit from playing a tape of terms you learned during the day.
Rudoy explained that it might mean someone studying while listening to music could benefit by having that same music played while they were asleep, but even that would require further study.
Another possible application, years down the line, would be helping patients with diseases caused by negative memories retain more positive ones instead.
"You could imagine playing sounds associated with the memories you want to keep…could possibly have the desired effect," said Rudoy. "It would be great if that would work that way but we're not sure."
McGaugh said the study was novel and interesting, but more research would be needed to understand why it happened, since the study also raised some questions.
"I don't think it solves all the questions," said McGaugh. "For example, why is it that doing it with subjects who are awake did not have the same effect? What is there about the failure of this treatment while awake? To me, it's extremely puzzling."
But he said not to discount sleep's value to a learner.
"In general, there's considerable evidence suggesting that sleep promotes the fixation of long-term memories of things that were learned before going to sleep," said McGaugh.