REM sleep or Rapid Eye Movement, is part of the sleep cycle, and in a normal nights sleep can occur a number of times, say 5 or 6 times.
As we sleep, we enter into differing levels or stages, 1 – 5, from a light sleep to a deep sleep, and theses stages will cycle round as mentioned perhaps 5 or 6 times.
Initially as we fall asleep we enter the 1st of 5 stages. This first stage is very light and is akin to being awake it is so close, and often people do not recognise stage as the body begins to relax.
The 2nd stage is a light sleep, where the heart rate slows down, the muscles relax and contract, and the body temperature begins to fall.
As sleep continues the sleep goes into the deepest stages, the 3rd and 4th, the 4th being the deepest, and the sleep will cycle between these two stages. The brain activity is very rhythmic and the body is quite still.
There are different levels of brain activity, and these are defined as:-
BETA high brain activity, awakened state
ALPHA a studious brain
THETA a daydreaming brain
DELTA low brain activity, deep sleep
It is during this Delta sleep, the 3rd and 4th stages, that the 5th stage is entered into, and this is defined as REM.
REM is characterised by quick, rapid movements of the eyes under the eyelids, and is often accompanied by the rigidity or the paralysis of the muscles, believed by sleep scientists to stop us enacting out our dreams, because it is believed that it is during REM sleep that we dream.
When the brain is monitored with an EEG, and the sleep cycle is studied with a Polysomnography (PSG), it will be seen that there is a high level of brain activity, the heart rate increases, and there could be twitching of the legs, fingers or facial muscles. Very similar to the wakeful state. This is compared to NREM (no rapid eye movement) sleep, which produces brain waves seen on an EEG that are typically slow and of high voltage, the breathing and heart rate are slow and regular, the blood pressure is low, and the sleeper is relatively still.
This REM sleep is often call paradoxical sleep, a mixture of encephalic (brain activity) states of excitement and muscular immobility.
The length of the REM sleep varies as the sleep cycle progresses, from a short 5 minute burst at the beginning to perhaps 90 minutes prior to waking naturally. This length and quality depends upon physical and psychological factors of the subject, for example depressives have shorter REM stages. Then, it depends if the subject is taking any drugs or stimulants, i.e. anti depressants such a s Prozac (click to read) tend to lengthen the REM stage. For me the herbal tea of St. John’s Wort, lengthens and gives me more intense dreams during REM, as it is a mild anti depressant.
Age also has a factor in the length of REM sleep and total amount of sleep. An infant will typically require 16 – 18 hours sleep a day, whereas a teenager will require say 9 hours, compared to and adult from 6.5 to 7.5 hours sleep. As we enter into old age, REM sleep lengthens.
Research has shown that subjects who do not have REM sleep through sleep deprivation may have memory problems, and may begin to hallucinate.
We have seen in earlier articles that the plasticity of the brain, the learning, passing short term memory to long term memory takes places in REM. We have also seen that REM clears the brain of unwanted working memory by having we can say a spring clean.
As stated above, REM sleep is believed to produce dreams. I say the word “believe” as research I have recently seen may indicate dreams are produced both in REM and NREM sleep.
For participants and people who practice hypnosis, REM phenomenon or REM signs can be clearly seen, the movement of the eyes under the eyelids, the rigidity of the body when catalepsy is induced, changes in muscle tone, changes in breathing, all producing a sleep like state that Dr. James Braid (James Braid 1796 – 1860 the Father of Hypnosis) coined the name of “hypnosis“, a sleep like state.
Once we understand hypnosis, we understand that it is not sleep, the client is fully aware of everything that is happening to them, and has full control, unlike sleep REM were the conscious mind is switched off.
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