What purpose does the Rapid Eye Movement stage of sleep serve? I’ve heard that people who are deprived of REM sleep but allowed to experience the other stages of sleep do not appear to suffer any ill effects.
So why did this trait evolve?
Thanks.
No-one knows. REM deprivation in animals leads to various behavioural and physiological effects (e.g., changes in learning behaviour), and ultimately death. Total REM deprivation in humans isn’t possible, AFAIK, and I doubt any study has been carried out in humans that truly pushes the envelope of sleep deprivation anywhere near that seen in animal research. Sleep deprivation (and REM deprivation) in humans does lead to measurable effects, behaviourally and physiologically - so sleep / REM are certainly doing something.
Some theories about REM suggest a role in consolidation of learning. Used to be quite a popular theory. Not sure if I still is, and TBH I don’t think this was really much more than a hypothesis, anyway.
Personally, I think REM sleep is analagous to a computer’s system scan and/or defragmentation. While the logical portion of the brain (the part that says: "this input makes no bleeping sense) is off to bed, the mind goes through all of its data.
This is factually incorrect. People who experience inadequate REM sleep because of sleep disturbance, sleep apnea, drug or alcohol abuse, etc, DO display many ill effects, including but not limited to irratability, lack of ability to concentrate, poor short term memory, depression, etc. etc.