In my last blog we discussed at length the different stages of sleep, namely non-REM and REM, the biological need for sleep to stay alive, and started discussing what some researchers believe may be the function of some portions of non-REM sleep. We reviewed how there is some evidence linking declarative memory (memory of facts and figures) to slow wave sleep and procedural memory (the ability to perform tasks like riding a bike or playing a musical instrument) to stage 2 sleep. Now for the really big question- what does REM have to do with all this? Or as a leading sleep researcher, Dr. Jerome Siegel puts it, “REM sleep is the proverbial riddle wrapped in a mystery inside an enigma”.
One interesting fact about REM sleep that shows its importance (the same is true for slow wave sleep), is that when someone is sleep deprived for a few days and has reduced REM sleep, the body tries to “repay” that debt by increasing REM sleep in the following days. If REM didn’t serve an important function, then why bother?
As we mentioned in my last blog, it would appear that an ideal time for there to be repair of the “damage” that occurs to brain during wake is during non-REM sleep. This would seem not to be the case for REM, because during REM the brain is highly active, just with an essentially paralyzed body. However, one group of brain cells actually turn themselves off during REM, these are collectively known as monoamines and include brain chemicals such as serotonin, norepinephrine, and histamine. These chemicals, or neurotransmitters (because they send signals between brain and nerve tissue), may need to be turned off to give the tissue that receives their messages time to “rest”. In other words, if the signals are constantly sent from these transmitters there is an overload of response which makes the receiving less sensitive. (This concept would be similar to the development of type 2 diabetes, that there is an overload of insulin at the receiving end, making the cells less sensitive to the effect of the insulin.) So the possibility remains that a “brain repair” is taking place during REM, as well.
One old disproved theory about REM was that the lack of REM sleep can lead to insanity. In fact, REM sleep deprivation might actually be important in treating depression. How this works is not clear, but many of the available antidepressants (such as Prozac and Zoloft) work by blocking the breakdown of the neurotransmitter serotonin.
What about memory you ask? This is a controversial topic, with some researchers feeling that REM is involved in memory while others say that there is no definite proof that any major memory function is occurring.
There is some evidence that REM sleep is extremely important for what is known as brain plasticity. Brain plasticity means that the brain retains the ability to reorganize its circuitry based on new experiences. When we learn something new, actual functional changes occur in our brains to help cement that knowledge in place.
More on this idea and how it is important to sleep in my next blog.
Published On: October 21, 2008