On the function of sleep
The nice NYT article on the function of sleep follows on a recent NIH-funded Nature insight series.
Some interesting facts from the NYT article:
- Sleep patterns vary greatly. Some bats sleep 20 hours, giraffes get 2 hours. (hmmm… grad students might be evolving toward giraffes…)
- Sleep has recently been found to occur in invertebrates too. Alternatively stated: Sleep is evolutionarily very old.
- Slow wave sleep is also found in fruit flies. (Divergence from fruit flies for us was 600 million years ago.)
- Some people don’t have any REM sleep. Behaviorally, these people are entirely normal, implying that it’s purpose might not be as obvious as one had thought (ie. required for the preservation of new memories, etc.)
- If you put a bunch of ducks in a row, the ones on the inside will sleep more often with both eyes closed. The ones on the outside will sleep with one eye open and it is (always?) the eye facing outward from the huddle. They are able to “sleep” one half of the brain at a time and, apparently, this sleeping with one eye open was lost in higher mammalian evolution. Fascinating.