The brain solves problems during sleep, study shows

Nobel Prize winner Otto Loewi reportedly came across the crucial idea that proved his theory of chemical neurotransmission by simply waking up to it. Dmitri Mendeleyev figured how to arrange the chemical elements into the periodic table in a dream. Samuel Taylor Coleridge wrote the deliriously beautiful "Kubla Khan" when he awoke.

The mysterious experience of waking and knowing -- not just thinking but knowing -- the solution to a problem is entirely familiar, even to the non-Nobel Prize winners among us.

An avalanche of inspirational literature, audiotapes, videos, and seminars promotes the idea that sleep leads to insight. But the evidence for a connection between the two has been entirely anecdotal -- until this week. In last week's issue of Nature, Ulrich Wagner, Jan Born and colleagues at the Universities of Lubeck and Cologne describe an experiment showing that when you sleep, your brain grinds on, engaging with problems and even solving them.

The 66 experimental subjects received intensive training in how to complete a mathematical task that could be solved by plowing through step-by-step -- or with a short-cut solution. Following the training, some slept while others stayed awake. They then were tested again. The scientists found that the sleepers were twice as likely as the nonsleepers to have an "aha" moment and jump from the beginning of the problem to the end in no time at all.

The advantage gained by the snoozers cannot be explained by exhaustion. One group of subjects trained on the problem in the evening, slept on it, and was retested the next day. Another group trained in the evening, stayed awake overnight, and was retested the next day. The third group trained in the morning, and was retested that evening. This group, just like the group that stayed awake all night, was still outperformed 2 to 1 by the subjects who had had a siesta.

But don't go back to bed just yet. Dozing your way through life's big questions requires more than Z's. Consciously wrestling with the problem first, whether for a day or a decade, is crucial in igniting unconscious problem-solving.

The researchers concluded that sleep is not just rest, at least in the traditional sense. Jan Born explains that during slumber there is a playback of recently acquired memories, in this case, what participants learned during training. He believes that part of this playback involves integrating the newly acquired information into what is already known long term. The mental shuffling and filing is an active process of reorganization that can change the perspective on a puzzle and lead to smarter solutions.

What does this mean for the United States -- a nation with one of the world's largest constituencies of insomniacs? Born and his colleagues didn't measure whether optimal nighttime problem-solving requires four hours of shut-eye or eight. So, is modern culture, with its longer and longer work hours, leading not just to a dangerously tired but ultimately a dumber America? It's not clear. We may have to sleep on it.