Rem Sleeps: Understanding The Science Of Sleep And Dreams

Sleep is a complex and mysterious process, and while we sleep, our bodies cycle through different stages. One of these stages is REM sleep, which stands for rapid eye movement sleep. During REM sleep, our eyes move rapidly behind closed eyelids, and our brain activity is similar to when we are awake. This stage of sleep is important for memory, mental concentration, and mood regulation. It also plays a role in dreaming, with most dreams occurring during this stage. While the first REM cycle is typically the shortest, lasting about 10 minutes, each cycle that follows is longer, with the final one lasting up to an hour. Understanding REM sleep is crucial as it accounts for about 25% of our total sleep time, and insufficient REM sleep can lead to negative consequences for our overall health.

REM sleep and dreaming

Sleep is divided into two main stages: rapid eye movement (REM) sleep and non-rapid eye movement (NREM) sleep. Dreaming typically occurs during the REM stage of sleep, which is characterised by relaxed muscles, quick eye movement, irregular breathing, elevated heart rate, and increased brain activity.

During REM sleep, your eyes move rapidly behind closed eyelids, and your heart rate and breathing speed up. Your brain is highly active, and you experience temporary muscle paralysis, which prevents you from acting out your dreams. The REM stage is usually when you dream, and your deepest sleep happens during non-REM sleep.

The first cycle of REM sleep occurs about 60 to 90 minutes after falling asleep. As part of a full night's sleep, you cycle through four stages of sleep multiple times: three stages of non-REM sleep, followed by one stage of REM sleep. Each cycle through all the sleep stages takes 90 to 120 minutes to complete. With each new cycle, you spend increasing amounts of time in REM sleep, with most of your REM sleep taking place in the second half of the night.

REM sleep is important for dreaming, memory, emotional processing, and healthy brain development. Dreaming mostly happens during REM sleep, and the dreams are usually more vivid than those during non-REM sleep. Your brain processes emotions during REM sleep, and the amygdala, which is responsible for processing emotions, is activated during this stage.

Memory consolidation also occurs during REM sleep, where your brain processes new learnings and motor skills from the day, committing some to memory and deciding which ones to delete. REM sleep also plays a role in brain development, especially in newborns, who spend most of their sleep time in this stage.

In summary, REM sleep is a crucial stage of the sleep cycle, characterised by rapid eye movements and increased brain activity. It plays an essential role in dreaming, memory consolidation, emotional processing, and brain development.

REM sleep and memory

REM sleep is important for memory consolidation, the process of stabilising new information into long-term storage. During REM sleep, the brain processes new learnings and motor skills from the day, deciding which to commit to memory, which to maintain, and which to delete.

REM sleep is also when emotional memories are processed, which can help people cope with difficult experiences. The brain's amygdala, which processes emotions, is activated during REM sleep.

Memory consolidation is thought to be optimised during sleep, and while recent evidence indicates that non-rapid-eye movement sleep (NREM) is directly involved in memory consolidation, the role of REM sleep in this process has been more controversial. This is due to the difficulty in isolating neural activity during REM sleep. However, recent work using a combination of electrophysiological recording and optogenetic techniques has demonstrated that neural activity during REM sleep is required for spatial and contextual memory consolidation.

REM sleep makes up about 25% of total sleep time in adults, but babies and children need more REM sleep, and the older we get, the less we need.

REM sleep and mental health

REM sleep is important for mental health as it plays a role in emotional processing and memory consolidation. During REM sleep, the brain processes emotions and consolidates new learnings and motor skills from the day, committing some to memory and deciding which ones to delete.

REM sleep is also when most dreams occur, and these dreams are usually more vivid than those that occur during non-REM sleep. Dreams are thought to be involved in emotional processing, and the amygdala (the part of the brain that processes emotions) is activated during this stage of sleep.

A lack of REM sleep can lead to symptoms such as trouble coping with emotions, trouble concentrating, a weakened immune system, and feeling groggy in the morning.

Disturbances to REM sleep have been linked to mental health conditions including depression and anxiety. One study found that REM sleep contributed to "cognitive distortions" of anxious depression, including negative self-appraisals, biased memory processing, and unpleasant dream content. Another study found that people with post-traumatic stress disorder (PTSD) had less REM sleep atonia, impaired noradrenergic modulation, and experienced nightmares outside of REM sleep around 25% of the time.

REM Sleep Behavior Disorder (RBD) is a parasomnia in which people physically act out their dreams, and it is associated with certain mental health conditions. RBD is strongly linked to neurodegenerative disorders, and around 97% of people with isolated RBD will develop Parkinson's disease, Lewy body dementia, or multiple system atrophy within 14 years of diagnosis.

REM sleep and physical health

REM sleep is vital for physical health, especially brain health and function. During REM sleep, the brain prunes its synapses, improving memory and problem-solving abilities. REM sleep also helps the brain process emotional memories, including those associated with fear, and is thought to aid in the development of the central nervous system.

The amount of REM sleep needed varies with age. Newborns spend about half their sleep time in REM sleep, which decreases to about 20% by age 20, and 17% by age 80.

Benefits of REM sleep include improved learning, mood regulation, brain development, and protection against dementia. A study published in the journal Neurology found that for every 1% reduction in REM sleep, there was a 9% increase in the risk of dementia.

If you don't get enough REM sleep, your body will naturally increase it the next night—a phenomenon known as REM rebound. To increase REM sleep, it's important to get more sleep overall. Sticking to a sleep schedule, limiting alcohol and caffeine, staying active, and relaxing before bed can help improve sleep.

REM sleep and sleep disorders

REM sleep behaviour disorder (RBD) is a parasomnia involving dream enactment behaviour associated with a loss of atonia during REM sleep. This can cause people to shout, punch, kick, or jerk in their sleep, potentially leading to injury. RBD has been linked to antidepressant use and narcolepsy, and there is a strong correlation with comorbid neurodegenerative alpha-synucleinopathies such as Parkinson's disease, Lewy body dementia, and multiple system atrophy.

The diagnosis of RBD requires confirmation by an in-laboratory sleep study, which helps to identify abnormal behaviours during REM sleep and exclude other sleep disorders. Treatment focuses on injury prevention, the management of underlying disorders, and, in severe cases, pharmacological treatment using oral medications such as melatonin or clonazepam.

Other sleep disorders associated with abnormal REM sleep include narcolepsy, nightmare disorder, and obstructive sleep apnea. Narcolepsy involves a sudden loss of muscle tone, which may occur when a person falls into REM sleep instantly from a waking state. Nightmare disorder involves regular intense and distressing nightmares and can be brought on by stress, childhood trauma, and other frightening experiences. Obstructive sleep apnea causes lapses in breathing during sleep, often leading to a lighter sleep cycle and reduced REM sleep.

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