I've got another guest post over at Discover magazine: Is the Purpose of Sleep to Let Our Brains “Defragment,” Like a Hard Drive?
It's an expanded version of two Neuroskeptic posts(1,2) about the theory that the job of slow-wave sleep is to prune connections in the brain, connections which tend to become stronger while we're awake and might become too strong without periodic resetting.
One of the commenters on the Discover post pointed out that this idea a bit like a much older idea about sleep, from Francis Crick (of discovering-the-structure-of-DNA fame). Back in 1983, Crick and Graeme Mitchison proposed that dreaming sleep serves to help us "unlearn": The Function of Dream SleepTheir idea was a bit different, but it was really very elegant.
The sleeping brain, they said, is cut off from real sensory input, and is subject only to essentially random activity variations. However, sometimes these meaningless inputs ...
