Rapid Eye Movement Sleep and Good Sleep Habits

Rapid eye movement sleep (REM sleep or REMS) is a unique phase of sleep in mammals and birds, characterized by the random rapid movement of the eyes, accompanied by low muscle tone throughout the body, and the propensity of the sleeper to dream vividly. Electrical and chemical activity regulating this phase seems to originate in the brain stem and is characterized most notably by an abundance of the neurotransmitter acetylcholine, combined with a nearly complete absence of monoamine neurotransmitters histamine, serotonin, and norepinephrine. Experiences of REM sleep are not transferred to permanent memory due to the absence of norepinephrine.

What is sleep?

You may think nothing is happening when you sleep. But parts of your brain are quite active during sleep. And enough sleep (or lack of it) affects your physical and mental health. When you sleep, your body has a chance to rest and restore energy. A good night’s sleep can help you cope with stress, solve problems or recover from illness. Not getting enough sleep can lead to many health concerns, affecting how you think and feel. During the night, you cycle through two types of sleep: Non-Rapid Eye Movement (NREM) sleep and Rapid Eye Movement (REM) sleep.

What is Rapid eye movement sleep?

When you enter REM sleep, brain activity increases again, meaning sleep is not as deep. The activity levels are like when you’re awake. That’s why REM sleep is the stage where you’ll have intense dreams.

At the same time, major muscles that you normally control (such as arms and legs) can’t move. In effect, they become temporarily paralyzed.

Usually, REM sleep arrives about an hour and a half after you go to sleep. The first REM period lasts about 10 minutes. Each REM stage that follows gets longer and longer.

Percentage of Rapid eye movement sleep

The amount of REM sleep you experience changes as you age. The percentage of REM sleep:

• Is highest during infancy and early childhood.
• Declines during adolescence and young adulthood.
• Declines even more as you get older.

What else happens to the body in Rapid eye movement sleep?

Besides increased brain activity and muscle relaxation, your body goes through a series of changes during REM sleep. These changes include:

• Faster breathing.
• Increased heart rate and blood pressure.
• Penile erections.
• Rapid eye movement.

What is Non-rapid eye movement sleep?

Three stages make up Non-REM sleep:

Stage 1

This stage of light sleeping lasts for five to 10 minutes.

• Everything starts to slow down, including your eye movement and muscle activity.
• Your eyes stay closed. If you get woken from stage 1 sleep, you may feel like you haven’t slept. You may remember pieces of images.
• Sometimes, you may feel like you’re starting to fall and then experience a sudden muscle contraction. Healthcare providers call this motion hypnic myoclonic or hypnic jerk. Hypnic jerks are common and not anything to be concerned about as this occurrence is unlikely to cause any complications or side effects.

Stage 2

• This period of light sleep features periods of muscle tone (muscles partially contracting) mixed with periods of muscle relaxation.
• Your eye movement stops, your heart rate slows and your body temperature decreases.
• Brain waves become slower. Occasionally, you’ll have a burst of rapid waves called sleep spindles.
• Your body prepares to enter deep sleep.

Stage 3

• This stage is deep sleep.
• During this stage, your brain produces delta waves, very slow brain waves.
• It’s hard for someone to wake you up during this stage.
• You have no eye movement or muscle activity.
• If you’re woken up, you may feel groggy and disoriented for a few minutes.

What happens during Non-REM sleep?

During Non-REM stages, your body:

• Builds bone and muscle.
• Repairs and regenerates tissues.
• Strengthens the immune system.

As you age, you get less Non-REM sleep. Older adults get less deep sleep than younger people.

Rapid eye movement sleep Psychology

Dreaming

Rapid eye movement sleep (REM) has since its discovery been closely associated with dreaming. Waking up sleepers during a REM phase is a common experimental method for obtaining dream reports; 80% of neurotypical people can give some kind of dream report under these circumstances. Sleepers awakened from REM tend to give longer, more narrative descriptions of the dreams they were experiencing, and to estimate the duration of their dreams as longer. Lucid dreams are reported far more often in REM sleep. 

The mental events which occur during REM most commonly have dream hallmarks including narrative structure, convincingness, and incorporation of instinctual themes. Sometimes, they include elements of the dreamer’s recent experience taken directly from episodic memory. By one estimate, 80% of dreams occur during REM.

Effects of SSRIs

Previous research has shown that Selective Serotonin Reuptake Inhibitors (SSRIs) have an important effect on REM sleep neurobiology and dreaming. A study at Harvard Medical School in 2000 tested the effects of paroxetine and fluvoxamine on healthy young adult males and females for 31 days: a drug-free baseline week, 19 days on either paroxetine or fluvoxamine with morning and evening doses, and 5 days of absolute discontinuation.

Results showed that SSRI treatment decreased the average amount of dream recall frequency in comparison to baseline measurements as a result of serotonergic REM suppression. Fluvoxamine increased the length of dream reporting, the bizarreness of dreams as well as the intensity of REM sleep. These effects were the greatest during acute discontinuation compared to treatment and baseline days. However, the subjective intensity of dreaming increased, and the proclivity to enter REM sleep was decreased during SSRI treatment compared to baseline and discontinuation days.

Creativity

After waking from REM sleep, the mind seems “hyperassociative”—more receptive to semantic priming effects. People awakened from REM have performed better on tasks like anagrams and creative problem solving. Sleep aids the process by which creativity forms associative elements into new combinations that are useful or meet some requirement. This occurs in REM sleep rather than in NREM sleep.

Rather than being due to memory processes, this has been attributed to changes during REM sleep in cholinergic and noradrenergic neuromodulation. High levels of acetylcholine in the hippocampus suppress feedback from the hippocampus to the neocortex, while lower levels of acetylcholine and norepinephrine in the neocortex encourage the uncontrolled spread of associational activity within neocortical areas. 

Rapid eye movement sleep Timing

In the ultradian sleep cycle, an organism alternates between deep sleep (slow, large, synchronized brain waves) and paradoxical sleep (faster, desynchronized waves). Sleep happens in the context of the larger circadian rhythm, which influences sleepiness and physiological factors based on timekeepers within the body. Sleep can be distributed throughout the day or clustered during one part of the rhythm: in nocturnal animals, during the day, and in diurnal animals, at night. The organism returns to homeostatic regulation almost immediately after REM sleep ends.

In the weeks after a human baby is born, as its nervous system matures, neural patterns in sleep begin to show a rhythm of REM and Non-REM sleep. (In faster-developing mammals, this process occurs in utero). Infants spend more time in REM sleep than adults. The proportion of REM sleep then decreases significantly in childhood. Older people tend to sleep less overall but sleep in REM for about the same absolute time (and therefore spend a greater proportion of sleep in REM).

Rapid eye movement sleep Classification

Rapid eye movement sleep can be subclassified into tonic and phasic modes. Tonic REM is characterized by theta rhythms in the brain; phasic REM is characterized by PGO waves and actual “rapid” eye movements. Processing of external stimuli is heavily inhibited during phasic REM, and recent evidence suggests that sleepers are more difficult to arouse from phasic REM than in slow-wave sleep.

Deprivation effects of Rapid eye movement sleep

Selective REMS deprivation causes a significant increase in the number of attempts to go into the REM stage while asleep. On recovery nights, an individual will usually move to stage 3 and REM sleep more quickly and experience a REM rebound, which refers to an increase in the time spent in the REM stage over normal levels. These findings are consistent with the idea that REM sleep is biologically necessary. However, the “rebound” REM sleep usually does not last fully as long as the estimated length of the missed REM periods.

After the deprivation is complete, mild psychological disturbances, such as anxiety, irritability, hallucinations, and difficulty concentrating may develop and appetite may increase. There are also positive consequences of REM deprivation. Some symptoms of depression are found to be suppressed by REM deprivation; aggression may increase, and eating behavior may get disrupted. 

Possible functions of Rapid eye movement sleep

Some researchers argue that the perpetuation of a complex brain process such as REM sleep indicates that it serves an important function for the survival of mammalian and avian species. It fulfills important physiological needs vital for survival to the extent that prolonged REM sleep deprivation leads to death in experimental animals. In both humans and experimental animals, REM sleep loss leads to several behavioral and physiological abnormalities.

Loss of REM sleep has been noticed during various natural and experimental infections. Survivability of the experimental animals decreases when REM sleep is totally attenuated during infection; this leads to the possibility that the quality and quantity of REM sleep are generally essential for normal body physiology. Further, the existence of a “REM rebound” effect suggests the possibility of a biological need for REM sleep. While the precise function of REM sleep is not well understood.

Memory

Sleep in general aids memory. REM sleep may favor the preservation of certain types of memories: specifically, procedural memory, spatial memory, and emotional memory. In rats, REM sleep increases following intensive learning, especially several hours after, and sometimes for multiple nights.

Experimental REM sleep deprivation has sometimes inhibited memory consolidation, especially regarding complex processes (e.g. how to escape from an elaborate maze). In humans, the best evidence for REM’s improvement of memory pertains to learning of procedures—new ways of moving the body (such as trampoline jumping), and new techniques of problem solving. REM deprivation seemed to impair declarative (i.e. factual) memory only in more complex cases, such as memories of longer stories. REM sleep apparently counteracts attempts to suppress certain thoughts.

Neural ontogeny

REM sleep prevails most after birth and diminishes with age. According to the “ontogenetic hypothesis”, REM aids the developing brain by providing the neural stimulation that newborns need to form mature neural connections.

Sleep deprivation studies have shown that deprivation early in life can result in behavioral problems, permanent sleep disruption, and decreased brain mass. The strongest evidence for the ontogenetic hypothesis comes from experiments on REM deprivation, and from the development of the visual system in the lateral geniculate nucleus and primary visual cortex.

Defensive immobilization

Ioannis Tsoukalas of Stockholm University has hypothesized that REM sleep is an evolutionary transformation of a well-known defensive mechanism, the tonic immobility reflex.

This reflex, also known as animal hypnosis or death feigning, functions as the last line of defense against an attacking predator and consists of the total immobilization of the animal so that it appears dead. Tsoukalas argues that the neurophysiology and phenomenology of this reaction show striking similarities to REM sleep; for example, both reactions exhibit brainstem control, cholinergic neurotransmission, paralysis, hippocampal theta rhythm, and thermoregulatory changes.

Shift of gaze

According to the “scanning hypothesis”, the directional properties of REM sleep are related to a shift of gaze in dream imagery. Against this hypothesis is that such eye movements occur in those born blind and in fetuses in spite of lack of vision.

Also, binocular REMs are non-conjugated (i.e. the two eyes do not point in the same direction at a time) and so lack a fixation point. In support of this theory, research finds that in goal-oriented dreams, eye gaze is directed towards the dream action, determined from correlations in the eye and body movements of REM sleep behavior disorder patients who enact their dreams.

Oxygen supply to the cornea

Dr. David M. Maurice, an eye specialist and former adjunct professor at Columbia University, proposed that REM sleep was associated with oxygen supply to the cornea and that aqueous humor, the liquid between cornea and iris, was stagnant if not stirred. Among the supportive evidence, he calculated that if aqueous humor was stagnant, oxygen from the iris had to reach the cornea by diffusion through aqueous humor, which was not sufficient.

According to the theory, when the organism is awake, eye movement (or cool environmental temperature) enables the aqueous humor to circulate. When the organism is sleeping, REM provides the much-needed stir to the aqueous humor. This theory is consistent with the observation that fetuses, as well as eye-sealed newborn animals, spend much time in REM sleep, and that during normal sleep, a person’s REM sleep episodes become progressively longer and deeper into the night. 

Other theories

Another theory suggests that monoamine shutdown is required so that the monoamine receptors in the brain can recover to regain full sensitivity.

The sentinel hypothesis of REM sleep was put forward by Frederick Snyder in 1966. It is based upon the observation that REM sleep in several mammals (the rat, the hedgehog, the rabbit, and the rhesus monkey) is followed by a brief awakening. This does not occur for either cats or humans, although humans are more likely to wake from REM sleep than from NREM sleep. Snyder hypothesized that REM sleep activates an animal periodically, to scan the environment for possible predators. 

What are good sleep habits?

Good sleep habits, also called good sleep hygiene, are practices to help you get enough quality sleep.

Dos

• Have a sleep schedule: Go to sleep and wake up around the same time every day, even on weekends and vacations.
• Clear your mind before bed: Make a to-do list early in the evening, so you won’t stay awake in bed and worry about the next day.
• Create a good sleep environment: Make sure your bed and pillows are comfortable. Turn down the lights and avoid loud sounds. Keep the room at a comfortable temperature.
• Exercise every day: Stay active but try to avoid exercising during the few hours right before bed.
• Relax: Before bed, take a warm bath, read or do another relaxing activity.
• See your healthcare provider: If you’ve been having trouble sleeping or feel extra drowsy during the day, talk to your provider. There are many treatments available for sleep disorders.

Don’ts

• Consume caffeine, nicotine, and alcohol late in the day: These substances can interfere with your ability to fall and stay asleep.
• Lie in bed awake: It’s better to do a soothing activity, like reading, until you feel tired.
• Nap during the day: A short nap (less than 30 minutes) is OK if you’re very sleepy. But try to avoid naps after 3 p.m.
• Think negative thoughts: Try to avoid a negative mindset when going to bed, such as, “If I don’t get enough sleep now, I won’t get through my day tomorrow!”
• Use electronics right before bed: Electronics, such as your phone or tablet, can interfere with your body’s production of melatonin. This hormone gets released before bed to help you feel tired.

Siddha remedies for Good sleep

 

Reference: https://en.wikipedia.org/wiki/Rapid_eye_movement_sleep