HETANEWS.com – Rapid eye movement, or REM sleep, is the final phase of the four-stage cycle that occurs during sleep. Unlike non-REM sleep, the fourth phase is characterized by increased brain activity and autonomic nervous system function, which is more similar to that seen during the waking state.
Similar to the non-REM sleep stage, this sleep stage is primarily controlled by the brainstem and hypothalamus with additional contributions from the hippocampus and amygdala. In addition, REM sleep is associated with an increased occurrence of vivid dreams.
Although non-REM sleep is associated with rest and recovery, the purpose and benefits of REM sleep are still unknown. However, many theories hypothesize that REM sleep is beneficial for learning and memory formation.
What is REM Sleep?
REM sleep is the stage of active sleep characterized by increased brain wave activity, a return to autonomic functioning in the waking state, and dreams with associated paralysis.
The brain stem, especially the pons and midbrain, and the hypothalamus are the main areas of the brain that control REM sleep with hormone secreting “REM-on” and “REM-off” cells.
The most vivid, complex, and emotional dreams occur during REM sleep.
The benefits of REM sleep are uncertain, but may be related to learning and memory retention.
REM definition
REM sleep is often described as a “paradoxical” sleep state because of the increased activity following non-REM sleep. The three previous stages of sleep, known as non-REM or N1, N2, and N3, occur initially during the sleep cycle to progressively slow down bodily functions and brain activity.
However, after the occurrence of N3 sleep (the deepest sleep stage), the brain signals the onset of a more aroused state.
As the name implies, the eyes move quickly to the side during REM sleep. Autonomic functions such as heart rate, respiratory rate, and blood pressure begin to increase toward their waking values.
However, because this period is often associated with dreams, the activity of the major limb muscles is temporarily paralyzed. Twitching can still be observed in smaller muscle groups.
REM sleep is the longest period of the sleep cycle and lasts 70 to 120 minutes. As sleep duration progresses, the sleep cycle favors an increase in the time spent in REM sleep. The proportion of time spent in this phase is determined by a person’s age.
All stages of sleep are present in newborns, but babies have a much higher percentage of non-REM slow wave sleep. The REM sleep ratio gradually increases with age until it reaches 20-25% of the sleep cycle in adults.
REM and Your Brain
During REM sleep, brain wave activity as measured on the electroencephalogram (EEG) also increases, compared to the slower wave activity seen during non-REM sleep.
N1 sleep exhibits a slowing of the normal alpha wave pattern noted during the waking state. N2 sleep introduces K waves, or high-voltage long waves lasting up to 1 second, and spindle sleep, or periods of low voltage and high frequency spikes.
N3 sleep is characterized by delta waves, or high-voltage, slow, and irregular activity.
However, the EEG obtained during REM sleep shows a sleep pattern of low voltage and fast waves, some alpha waves, and transmitted muscle twitches with rapid eye movements.
These readings were also more variable than those observed during non-REM sleep, with random spiking patterns sometimes more fluctuating than visible activity while awake.
The main parts of the brain that are activated during REM sleep are the brainstem and hypothalamus. The pons and midbrain, in particular, and the hypothalamus contain specialized cells known as “REM-on” and “REM-off” cells.
To induce the transition to REM sleep, REM cells secrete hormones such as GABA, acetylcholine, and glutamate to instruct rapid eye movement, suppression of muscle activity, and autonomic changes.
REM-off cells, as the name implies, induce REM sleep by the secretion of stimulating hormones such as norepinephrine, epinephrine and histamine. The hypothalamus also contains stimulating cells known as orexin neurons, which secrete the hormone orexin.
This hormone is necessary to maintain wakefulness and wakefulness from sleep and is often reduced or absent in people with sleep disorders. The hippocampus and amygdala are also involved in REM sleep, particularly during dream periods.
This area of the brain is best known for its function in memory and emotion regulation. The EEG will show increased hippocampal and amygdala activity in the presence of high-voltage regular waves known as theta waves.
REM Dreams and Sleep
Although dreams can occur during other sleep stages, the most vivid dreams occur during REM sleep.
These dreams are often complicated and emotional experiences of an imagined life, most often associated with sadness, anger, fear, or fear.
A person can also remember dreams more easily when awakened from REM sleep than non-REM sleep. The purpose of dream content is currently not understood.
Historically, the neurologist and father of psychoanalysis Sigmund Freud stated that dreams are a representation of the subconscious mind, and therefore each dream has a very important meaning.
His dream interpretation, however, is not a universally accepted theory. The opposing hypothesis proposes that dream content is the result of random brain activity that occurs during REM sleep, not meaningful interpretive experience.
Benefits of REM Sleep
Sleep in general is necessary for health and well-being, as mild sleep deprivation increases the risk of chronic health conditions and severe sleep deprivation can cause hallucinations or even death.
Although non-REM sleep is necessary for survival, the benefits of REM sleep remain inconclusive. Studies in which participants did not sleep in REM sleep when awake showed no obvious side effects.
Some drugs, including MAO antidepressants, cause a drastic decrease in REM sleep without any problems for patients even after years of treatment.
Due to the lack of conclusive evidence, many hypotheses exist regarding the benefits of REM sleep. One of the hypothesized benefits has to do with the link between REM sleep and dreams.
This theory suggests that certain negative behaviors that must be “unlearned” are trained through dreams. Actions, events and sequences associated with frightening situations are often the subject of dreams and are therefore appropriately removed from neural networks.
REM sleep is also proposed to help transfer memories from the hippocampus to the cerebral cortex. In fact, the occurrence of non-REM and REM sleep cycles is often thought to promote the body’s physical and mental rest and aid in memory formation.
Source: thoughtco.com
