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The Sleep That Repeats

Although sleep may feel like a blank, "turned off" time, it's actually when our bodies are doing all sorts of useful things--and so are our brains.A study at Duke University Medical center suggests that one of the things sleep is good repeating.

First, the experimenters wired different areas of some rats' brains so they could monitor electrical activity. Next they gave the rats something to play with. These were items such as a ball on a spring, a tube that dispensed cereal, a bristly brush--just the kinds of things rats love to examine at length.

That's just what they did. While the rats were exploring, the researchers noticed which regions of their brains were being activated--regions such as the hippocampus and the thalamus.

Later on, the rats went to sleep. Lo and behold, when the rats went into a stage called "slow-wave sleep," the brain activity patterns the researchers had seen when the rats were exploring the objects reappeared. Over the next two days this same activity was spotted again and again.

This result hints that in slow-wave sleep, the rats' brains were repeating information gathered during wakefulness. That looks like one stage of memory formation taking place: don't forget, the cereal is inside the tube!...The tube!...The tube!

More research needs to be done to understand exactly what is happening during other stages of sleep, as well as what this information may tell us about human sleep and learning. But the study does suggest that one thing we do when we repeat.

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