Sleep is still mysterious in many ways and scientists do not understand everything about it.
In 2005 the American Association for Advancement of Science listed 100 unanswered questions as a way of highlighting the need for most science. “Why do we sleep?” was among the questions.
- Long-term effects of short sleep and long sleep
- We experience sleep as restorative. What, exactly, is being restored?
- How memory works (and how sleep works with this).
- Reasons for sleep (biological), including function of REM sleep
Evolutionary reasons for sleep
- How hard-wired are chronotypes?
- Causes of parasomnias
- The different levels of detail that scientists study – neuronal, circuits, and behavior – how do they relate to each other.
- The biochemical substrates of not just sleep but also daytime sleepiness
- How valid is the 2-process model? Are circadian and homeostatic processes independent or linked, and if linked, how linked? Some scientific work indicates that there is a connection.
- How valid is the theory of cortical columns and the neural network switching for turning on and off sleep?
- How small can a group of neurons get and continue to go through sleep-like cycles, and how does this local sleep-like behavior differ from whole brain sleep?
Hacking of sleep – can it work. Can we isolate REM? Why sleep is divided between REM and NREM and the evolution of REM? Can we shorten sleep requirements?
- Can we use electrical stimulation of the brain as a means of treating sleep disorders or altering sleep architecture and needs.
- Can we prevent subtle aged-related changes in the brain that result in pervasive insomnia among seniors?
Why do we sleep? here is no scientific consensus on the evolutionary reasons for sleep. It’s a mystery. But you can’t resist it for long. Sleep deficit can be cured only by getting some sleep.
Only in the past few decades have scientists begin to unravel the mysteries of sleep. During the 1950s investigators first documented rapid eye movement (REM) and started to describe the brain states that make up the stages of sleep.
Further investigation into basic neurobiology, behavioral and physiological emergent systems, and epidemiology revealed much about sleep. Advances are occurring at an unprecedented rate in the 21st century and scientists are learning more about sleep. Medications have been developed to help people sleep and the discovery of orexin neuropeptides in the 1990s may soon lead to a new class of sleep medicines.
Many mysteries remain. Scientists still have an inadequate understanding of the physiology of sleep and the pathology of sleep disorders. Further, although depression and neurodegenerative diseases are associated with abnormal sleep, nobody knows if there is a cause-and-effect in place, and if so, which way it runs.