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Monday, August 18, 2008

Neuroscience: Yes, we do think while we are asleep

In "Sleep on It: How Snoozing Makes You Smarter" Robert Stickgold and Jeffrey M. Ellenbogen reveal, "During slumber, our brain engages in data analysis, from strengthening memories to solving problems" (Scientific American Mind - August 7, 2008):
The latest research suggests that while we are peacefully asleep our brain is busily processing the day's information. It combs through recently formed memories, stabilizing, copying and filing them, so that they will be more useful the next day. A night of sleep can make memories resistant to interference from other information and allow us to recall them for use more effectively the next morning. And sleep not only strengthens memories, it also lets the brain sift through newly formed memories, possibly even identifying what is worth keeping and selectively maintaining or enhancing these aspects of a memory. When a picture contains both emotional and unemotional elements, sleep can save the important emotional parts and let the less relevant background drift away. It can analyze collections of memories to discover relations among them or identify the gist of a memory while the unnecessary details fade-perhaps even helping us find the meaning in what we have learned.
Their research is a far cry from earlier theories that the brain shuts down when we are asleep. Apparently, sleep plays an active, not merely a passive role in learning, as a number of fascinating experiments show.

The fact that sleep plays at least a passive role in learning won't be news to anyone who has had to teach students who were up half the night partying and can't now remember their classroom number, let alone the topic we discussed in the last class. But consider this:
In a 2004 study Ullrich Wagner and others in Jan Born's laboratory at the University of L├╝beck in Germany elegantly demonstrated just how powerful sleep's processing of memories can be. They taught subjects how to solve a particular type of mathematical problem by using a long and tedious procedure and had them practice it about 100 times. The subjects were then sent away and told to come back 12 hours later, when they were instructed to try it another 200 times.

What the researchers had not told their subjects was that there is a much simpler way to solve these problems. The researchers could tell if and when subjects gained insight into this shortcut, because their speed would suddenly increase. Many of the subjects did, in fact, discover the trick during the second session. But when they got a night's worth of sleep between the two sessions, they were more than two and a half times more likely to figure it out-59 percent of the subjects who slept found the trick, compared with only 23 percent of those who stayed awake between the sessions. Somehow the sleeping brain was solving this problem, without even knowing that there was a problem to solve.
I'm not so sure the sleeping brain did not know there was a problem to solve - the prospect of waking up to another two hundred iterations of a tedious procedure must have set the little grey cells churning, so to speak.

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