Evie Summers
Rapid Eye Movement (REM) sleep is the fourth of four stages of sleep. It is characterised by quick, random eye movement, low muscle tone, irregular breathing, elevated heart rate, and increased brain activity. Most adults need about two hours of REM sleep each night. It is also known as paradoxical sleep, as the body behaves in a similar way to when it is awake. Dreaming is associated with REM sleep, but it also plays a role in memory consolidation, emotional processing, brain development, and learning.
| Characteristics | Values |
|---|---|
| Phase | Fourth out of four stages of sleep |
| Eye movement | Rapid and random |
| Muscle tone | Low or relaxed |
| Dreams | Vivid |
| Core body and brain temperature | High |
| Skin temperature | Low |
| Brain waves | Rapid, low-voltage, desynchronized |
| Neurotransmitters | Acetylcholine, histamine, serotonin, norepinephrine |
| Sleep cycle | Occurs 4 times in a 7-hour sleep |
| Duration | 20-25% of an adult's sleep cycle |
| Functions | Memory consolidation, emotional processing, brain development, dreaming |
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What You'll Learn
REM sleep is the fourth of four stages of sleep
Rapid eye movement (REM) sleep is the fourth of four stages of sleep. It is a unique phase of sleep in humans and other mammals, birds, and some reptiles. REM sleep was first discovered in the 1950s when scientists observed infants exhibiting distinct periods of rapid eye movement during sleep.
During REM sleep, the eyes move rapidly in various directions, and dreams often occur. The body experiences a temporary loss of muscle tone, known as atonia, which may serve as a protective mechanism to prevent individuals from acting out their dreams and injuring themselves. The transition to REM sleep brings about significant physical changes, including fluctuations in respiration, thermoregulation, and circulation. The heart rate increases, and breathing becomes irregular.
In addition to dreaming, REM sleep plays a crucial role in memory consolidation, emotional processing, brain development, and learning. It typically occurs within 90 minutes of falling asleep and accounts for approximately 20-25% of an adult's sleep cycle. As the sleep cycle repeats, REM sleep occurs several times throughout the night.
REM sleep can be further subclassified into tonic and phasic modes. Tonic REM is characterised by theta rhythms in the brain, while phasic REM is marked by PGO waves and the actual rapid eye movements. During phasic REM, the processing of external stimuli is heavily inhibited, and individuals are more challenging to arouse compared to slow-wave sleep.
The absence of sensory stimulation during REM sleep can lead to hallucinations. Additionally, the brain exhibits increased electrical and chemical activity, particularly in the brain stem, with a notable abundance of the neurotransmitter acetylcholine.
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Dreaming occurs during REM sleep
During REM sleep, the brain is highly active, and brain waves become more variable. The body abruptly loses muscle tone, a state known as REM atonia, which may be a protective mechanism to prevent injury that could result from acting out dreams. The absence of visual and auditory stimulation during REM sleep can also cause hallucinations.
REM sleep typically starts within 90 minutes of falling asleep and occurs several times while a person is resting. It accounts for approximately 20-25% of an adult's sleep cycle and over 50% of an infant's. As sleep cycles continue, they shift towards a higher proportion of REM sleep.
REM sleep is involved in several important functions, including brain development, memory consolidation, emotional processing, and dreaming. Most dreams occur during REM sleep, and it is believed that the brain processes information and consolidates memories during this stage. A lack of REM sleep may negatively impact physical and mental health and impair an individual's ability to differentiate between threatening and non-threatening stimuli.
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The brain is highly active during REM sleep
Rapid eye movement (REM) sleep is one of four stages the brain moves through while sleeping. During REM sleep, the eyes move rapidly in various directions, and dreams can occur. The body abruptly loses muscle tone, a state known as REM atonia, which may be a protective mechanism to prevent injury that may result from "acting out" our dreams.
REM sleep is characterised by increased brain activity, with brain waves becoming more variable. The brain processes information and consolidates memories during sleep, and a lack of REM sleep may reduce a person's ability to differentiate between threatening and non-threatening stimuli. This stage of sleep may also play a role in learning, memory, mood, and brain development.
The transition to REM sleep brings about marked physical changes, including an increase in heart rate, irregular breathing, and fluctuations in thermoregulation and circulation. The core body and brain temperatures increase, while the skin temperature decreases. Organisms in REM sleep suspend central homeostasis, allowing these fluctuations to occur.
The electrical bursts that precede REM sleep are called ponto-geniculo-occipital waves (PGO waves) and originate in the brain stem. The brain stem, particularly the pontine tegmentum and locus coeruleus, is also the source of the electrical and chemical activity regulating this phase of sleep. This phase is characterised by an abundance of the neurotransmitter acetylcholine and a near absence of monoamine neurotransmitters such as serotonin and norepinephrine.
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REM sleep can be subclassified into tonic and phasic modes
Rapid eye movement (REM) sleep is a unique phase of sleep in humans and other mammals, reptiles, and birds. It is characterised by the random rapid movement of the eyes, low muscle tone throughout the body, and the propensity of the sleeper to dream vividly.
During REM sleep, the eyes move rapidly behind closed eyes, the heart rate speeds up, and breathing becomes irregular. The brain is highly active during this stage, and the body operates similarly to how it does when awake. Researchers have hypothesised that the temporary loss of muscle tone during REM sleep is a protective measure to prevent people from acting out their dreams and injuring themselves.
REM sleep plays a role in memory consolidation, emotional processing, brain development, and dreaming. It is involved in a host of important functions, and selective REM sleep deprivation causes a significant increase in attempts to enter the REM stage during sleep.
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The absence of sensory stimulation during REM sleep can cause hallucinations
Rapid eye movement (REM) sleep is a unique phase of sleep in humans and other mammals, birds, and reptiles like the Australian bearded dragon. It is characterised by rapid movement of the eyes, low muscle tone, irregular breathing, elevated heart rate, and increased brain activity. The first cycle of REM sleep occurs about 60 to 90 minutes after falling asleep. During REM sleep, the body suspends homeostasis, allowing for large fluctuations in respiration, thermoregulation, and circulation.
Sleep paralysis, a condition where a person is temporarily paralysed but perceptually alert, is often associated with hypnagogic hallucinations. These hallucinations can occur during the transition from REM sleep to wakefulness and may involve sensing the presence of another person in the room or even on their chest. About 80% of people may experience hallucinations if they are severely sleep-deprived.
Hypnagogic hallucinations differ from nightmares as they are not associated with fear and do not involve a story or interaction. They often involve moving shapes, colours, and images, as well as background sounds. While the exact cause of hypnagogic hallucinations is unknown, they are believed to be related to disruptions in multisensory processing and the interpretation of visual stimuli.
In summary, the absence of sensory stimulation during REM sleep can lead to hallucinations due to the heightened brain activity and the lack of external stimuli to ground the individual in their surroundings. This can result in the perception of things that are not actually present, known as hallucinations. While hypnagogic hallucinations associated with sleep paralysis are typically harmless, chronic sleep deprivation and underlying mental health issues can contribute to more severe hallucinations and sleep disorders.
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Frequently asked questions
REM stands for rapid eye movement sleep, which is a unique phase of sleep in mammals (including humans) and birds. It is characterised by random rapid movement of the eyes, low muscle tone throughout the body, and the propensity of the sleeper to dream vividly.
During REM sleep, your eyes move rapidly behind your closed eyes, your heart rate speeds up, and your breathing becomes irregular. Your brain is highly active during this stage, and brain waves become more variable. Most adults need about two hours of REM sleep each night.
A lack of REM sleep may have adverse implications for physical and mental health. Research suggests that a lack of REM sleep may reduce a person's ability to differentiate between threatening and non-threatening stimuli and respond accordingly. It may also increase a person's risk of experiencing migraines in the days following sleep deprivation.
