Herbie Murray
REM sleep, or rapid eye movement sleep, is the fourth and final stage of the sleep cycle. It is characterised by increased brain activity, limited muscle movement, darting eye movement, fluctuating respiration and heart rate, and vivid dreams. REM sleep is important for brain health and function, contributing to memory consolidation, improved learning, and mood regulation. During a full night's sleep, individuals cycle through different stages of sleep multiple times, with the first REM stage typically lasting around 10 minutes, and subsequent stages lengthening, with the final stage lasting up to an hour.
| Characteristics | Values |
|---|---|
| Occurrence in sleep cycle | The first REM cycle occurs about 60 to 90 minutes after falling asleep. Each cycle lasts about 80 to 100 minutes, with four to six cycles per night. |
| Proportion of sleep | REM sleep makes up about 20% of total sleep time for adults, decreasing slightly to about 17% by age 80. |
| Dreaming | REM sleep is when most dreams occur, including vivid dreams. |
| Eye movement | The eyes move rapidly behind closed eyelids. |
| Muscle movement | Muscles in the arms and legs become temporarily paralysed, preventing people from acting out their dreams. |
| Heart rate and blood pressure | Heart rate, blood pressure, and breathing increase to levels similar to those experienced when awake. |
| Brain activity | Brain activity increases, resembling wakefulness. The brain prunes its synapses, improving memory and problem-solving abilities. |
| Learning and memory | REM sleep stimulates brain areas that help with learning and memory consolidation. |
| Mood regulation | REM sleep helps the brain process emotional memories, including fear, and regulates mood. |
| Brain development | It is thought to aid in the development of the central nervous system, including the brain and spinal cord. |
| Protection against dementia | Reduced REM sleep is associated with an increased risk of developing dementia. |
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What You'll Learn
Dreaming and brain activity
During REM sleep, the brain exhibits fast, low-amplitude, desynchronised neural oscillation (brain waves) that resemble the patterns seen when awake. The brainstem plays a key role in regulating this phase, with electrical and chemical activity originating in this region. Specifically, the pontine tegmentum and locus coeruleus are involved in neural activity during REM sleep. The brainstem also gives rise to electrical bursts called "ponto-geniculo-occipital waves" (PGO waves), which mark the transition to REM sleep and bring about significant physical changes.
The cortical and thalamic neurons are more active during REM sleep than in deep non-REM sleep. Human theta wave activity is prominent in the hippocampus and cortex during this stage. The brain's electrical connectivity differs from that seen during wakefulness, with frontal and posterior areas showing less coherence in most frequencies. This altered connectivity may contribute to the chaotic nature of dreams. However, the right and left hemispheres of the brain exhibit increased coherence during REM sleep, particularly during lucid dreams.
The brain's energy usage during REM sleep, as measured by oxygen and glucose metabolism, equals or even surpasses that of wakefulness. In contrast, non-REM sleep is associated with 11-40% lower brain energy consumption.
Beyond dreaming, REM sleep is crucial for brain development and function. It aids in the development of the central nervous system, including the brain and spinal cord. During this stage, the brain prunes its synapses, enhancing memory and problem-solving abilities. REM sleep also facilitates emotional regulation by helping the brain process emotional memories, including those associated with fear.
In summary, while dreaming is a prominent feature of REM sleep, this stage involves much more than just dreaming. The increased brain activity and unique neural patterns observed during REM sleep contribute to essential functions such as memory consolidation, emotional processing, and brain development.
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Muscle paralysis
During REM sleep, the body experiences muscle paralysis, also known as sleep paralysis, whereby the muscles in the arms and legs relax and become temporarily paralysed or unable to move. This typically occurs just before falling asleep or upon waking up, and usually lasts for a few seconds to a few minutes. While the exact reason for this paralysis is not known, it is believed that this phenomenon prevents people from acting out their dreams, which can be vivid during this stage of sleep. This paralysis is a natural part of the sleep cycle, and while it can be a frightening experience, it is not harmful to one's health.
REM sleep behaviour disorder is a condition where muscle paralysis does not occur during REM sleep, allowing people to act out their dreams, which can result in physical injury. This condition can be diagnosed through a sleep study that evaluates muscle tone during sleep.
Sleep paralysis can be treated by addressing the underlying causes, which may include stress or poor sleep habits. Medication can also be used to prevent entry into the REM stage of sleep or to treat underlying mental health conditions or sleep disorders. Improving sleep habits and hygiene can also help reduce the occurrence of sleep paralysis.
While there is no way to stop a sleep paralysis episode once it is happening, it is possible to come out of it sooner by focusing on making small body movements, such as moving one finger and gradually increasing the movement. Sleep paralysis is a common experience, and most people may have at least one episode in their lifetime, often during periods of high stress or poor sleep.
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Heart rate and blood pressure increase
During REM sleep, the body experiences heightened activity that resembles wakefulness. This includes an increase in heart rate and blood pressure.
REM sleep is the fourth and final stage of sleep, during which people experience vivid and intense dreams. It is characterised by increased brain activity, limited muscle movement, darting eye movement, and fluctuating respiration and heart rate. The first period of REM sleep occurs about 60 to 90 minutes after falling asleep, and most adults need about two hours of REM sleep per night.
The heart rate during REM sleep can vary depending on the activity level occurring in the dream. If the dream is scary or involves physical activity, the heart rate rises as if the person were awake. This surge in activity during REM sleep may explain why vulnerable people often experience heart attacks and other events in the early morning hours, when REM sleep is more prevalent.
While the heart rate typically slows down during sleep, REM sleep is an exception. The increase in heart rate and blood pressure during REM sleep is a normal part of the body's sleep cycle. However, it is important to note that sleep problems and disorders can negatively impact heart and cardiovascular health, contributing to higher blood pressure and heart rate.
The amount of REM sleep needed changes with age. Newborns spend about half their sleep time in REM sleep, which gradually decreases to about 20% by the age of 20. As people age, the resting heart rate remains relatively stable unless they are taking medications that slow the heart rate.
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Learning and memory
Sleep has a significant impact on learning and memory. The process of sleep strengthens connections between brain regions, and some studies suggest it sharpens one's working memory. During REM sleep, the brain reviews things learned recently, deciding which items to keep in memory and which to delete. This process is called memory consolidation, and it occurs during both the non-rapid eye movement (NREM) and rapid eye movement (REM) sleep cycles. Memory consolidation is the process of preserving key memories and discarding excessive information.
The brain also sorts through various memories from the previous day during the NREM stages, filtering out important memories and eliminating other information. These selected memories become more concrete as deep NREM sleep begins, and this process continues during REM sleep. Emotional memories are also processed during the REM stage, which can help people cope with difficult experiences. Most dreaming occurs during REM sleep, and it is during this stage that the brain is highly active, interpreting and processing information from one's memories.
Research has shown that taking an afternoon nap increases learning capacity. A study tested two groups of subjects on a nondeclarative memory task. One group engaged in REM sleep, and the other did not (meaning they engaged in NREM sleep). The results showed that the group that engaged in REM sleep showed a significant increase in performance.
Additionally, the same patterns of brain activity that occur during learning have been found to recur during sleep, but at a faster rate. Sleep strengthens memories by weeding out less successful connections between neurons in the brain. This process is essential to prevent overactivity. The brain compensates for strengthening some synapses (connections) between neurons by weakening others, and this weakening process primarily occurs during sleep. This weakening allows for the strengthening of other connections while we are awake.
Overall, a good night's rest promotes good physical health and enables our brains to function properly, so getting the recommended amount of sleep each night is key to consolidating memories.
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Mood regulation
Sleep plays a crucial role in our lives, and the quality and quantity of sleep we get can significantly impact our health and well-being. One particular stage of sleep, known as REM sleep, is essential for various reasons, including mood regulation.
REM sleep, or Rapid Eye Movement sleep, is characterised by rapid eye movements, increased brain activity, and vivid dreaming. It typically occurs at the end of the night, with each REM episode lengthening during subsequent sleep cycles. During REM sleep, our brain processes emotional memories, including those associated with fear. This process of emotional regulation during REM sleep helps improve our mental concentration and overall quality of life.
The impact of REM sleep on mood regulation is significant. Studies have found that awakening during REM sleep can result in a negative mood and self-appraisal, with both men and women rating themselves less positively upon awakening from REM sleep compared to non-REM sleep. Additionally, disrupted REM sleep has been linked to a worse mood and mental health conditions such as depression and post-traumatic stress disorder (PTSD). Insomnia patients, for instance, often experience emotional dysregulation, demonstrating the correlation between REM sleep and emotional regulation.
Furthermore, REM sleep helps protect against certain mental health disorders. A study published in Neurology found that individuals who get less REM sleep may have an increased risk of developing dementia. Similarly, another study suggested that REM sleep physiology is altered in individuals with mood disorders, particularly depression. This highlights the importance of adequate REM sleep for mood regulation and overall mental health.
To optimise REM sleep for mood regulation, it is essential to prioritise overall sleep quality and quantity. Maintaining a consistent sleep schedule, limiting exposure to artificial light at night, and adopting calming rituals before bed can all contribute to improved REM sleep and, consequently, enhanced mood regulation.
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Frequently asked questions
REM stands for rapid eye movement. It is the fourth and final stage of sleep, during which most dreams occur. It is characterised by increased brain activity, limited muscle movement, darting eye movement, and fluctuating respiration and heart rate.
REM sleep plays a critical role in brain function, memory consolidation, and emotional health. It is also important for brain development, mood regulation, and protection against dementia.
Most adults need about two hours of REM sleep each night, which is approximately 20% of their total sleep time. However, this can vary depending on age and other factors. Newborns spend about half their sleep time in REM sleep, while older adults may experience a slight decrease in REM sleep with age.
