Sleep is underrated. This is somewhat puzzling. What would you pay for a pill that makes you feel better, be more productive, more creative, less likely to get Alzheimer’s and perhaps even lose some weight? Sleep does all of that without any side effects and – unlike exercise, which touts some of the same benefits – requires no effort at all. Part of the reason why we don't value sleep is probably due to the fact that we’re unconscious when it happens. From the outside, it appears that not much is being accomplished during sleep. Historically, lack of movement has been one of the defining features of sleep. It can be hard to tell the difference between a person who is sound asleep and one who has died, a confusion that features prominently in classic literature including Shakespeare’s Romeo and Juliet. But appearances can be deceiving.
The brain is hard at work while you are sleeping. There is a lot going on inside, from solidifying memories (called “memory consolidation”) to mood stabilization to the removal and elimination of toxic cellular waste products. This intense activity is reflected in complex patterns of brain waves that occur throughout the night. Brain waves are the combined electrical currents of millions of neurons. These waves are measured with EEG (“electro-encephalography”), by touching wires to a person’s scalp. EEG allows scientists to classify sleep into different stages. One of these sleep stages (“REM sleep”) features brain waves that are barely distinguishable from those during waking, although muscles are – with few exceptions – paralyzed during REM sleep. It is REM sleep that is most closely associated with some cognitive benefits of sleep, like learning and creativity. REM sleep is also when people are most likely to experience dreams. So the brain is very busy during REM sleep. The discovery of REM sleep about 50 years ago was one of the most important advances in sleep science.
Sleep is actively controlled and maintained by a complex interplay and balance between many brain regions. If one or more of these brain regions get out of synch, sleep becomes fractured. For instance, it is possible for someone to wake up from REM sleep without a corresponding release from the muscle paralysis (which is maintained by a different brain area), which can lead to a truly terrifying experience (called “sleep paralysis”). Conversely, if the paralysis during REM does not kick in, the sleeper will act out their dreams, which is called REM sleep behavior disorder.
There can be no denying that sleep is an active – and actively maintained – process. Sometimes, extremely active people forego sleep in a misguided effort to get a lot done. But the human mind and body can’t accomplish much without first sleeping, actively. So if you have a lot of stuff to get done, get busy sleeping.
Even during sleep, the brain is never truly at rest.
Phases where activation (purple) and deactivations(blue) are synchronized,
like in deep sleep, alternate with phases where they are not, like in REM sleep.