Such a tight mutual control of REM-on/off areas is why the finding is so important. It means that even a tiny bit of imbalance between those two areas could switch the entire brain state from one to the other. Why slow-wave and REM? Why sleep at all?

Although we now know a lot about brain oscillation in sleep, pressing questions remain unanswered. In slow-wave sleep, most of the neurons will participate in the slow-wave oscillations. In REM sleep, most of the neurons stay in the UP state. But why? We don't need to respond to the outside world during sleep, so why waste precious energy on an UP state? Furthermore, we all spend about one third of life asleep. Is it as big of a waste of time as it seems? Even worse, sleep seems to be dangerous since we are basically helpless to respond to threats, and when we lived in the wild, this could be fatal.

However, given all these hard questions, evolutionarily sleep is still conserved throughout the animal kingdom. So much so, that even a kind of earthworm (C. elegans) has been found to sleep from time to time. To me, sleep and the oscillation states must play important functions in the success of animals-we just need to find them! Memory consolidation is a good one, but we will need to know more in order to sleep without the guilt of wasting another night. Until that time, though, let's continue to enjoy the comfort of a good night's sleep.