Brain Basics: Understanding Rem Sleep And Brainwaves

Sleep is divided into two distinct phases: REM (rapid eye movement) sleep and non-REM sleep. Brain waves during REM sleep are very similar to those during wakefulness. REM sleep is characterised by darting movements of the eyes under closed eyelids and is the stage of sleep in which dreaming occurs. The brainwaves during REM sleep are mixed-frequency and are thought to be linked to memory consolidation and integration.

REM sleep is characterised by brain waves similar to those during wakefulness

Sleep is composed of several different stages, each with distinct patterns of brain wave activity. These brain waves can be visualised using electroencephalography (EEG) and differentiated by their frequency and amplitude. Sleep can be divided into two distinct phases: REM sleep and non-REM (NREM) sleep.

REM sleep, or rapid-eye-movement sleep, is characterised by darting movements of the eyes under closed eyelids. Brain waves during REM sleep are very similar to those observed during wakefulness. In contrast, NREM sleep is further subdivided into three distinct stages, each distinguished by unique patterns of brain waves.

During REM sleep, the brain exhibits mixed-frequency brain wave activity, likely due to dreams. The brain waves observed during this stage are typically associated with wakefulness and include alpha and beta waves. Alpha waves are present when a person is awake but relaxed, often with their eyes closed. Beta waves are the most common daytime brain waves and are associated with engaging activities such as problem-solving and other cognitive tasks.

The presence of brain waves typically associated with wakefulness during REM sleep suggests that this stage of sleep may serve a unique function. Indeed, REM sleep has been implicated in memory consolidation, emotional processing, and regulation. If a person is deprived of REM sleep, they will spend more time in this stage when they next sleep, in what is known as REM rebound. This suggests that REM sleep is essential and regulated by the body.

Dreaming occurs during REM sleep

During REM sleep, the brain is highly active, and the body is temporarily paralysed. This is known as REM atonia, and it affects all voluntary muscles, except those that control breathing and circulation. This is why people do not act out their dreams. However, in people with REM sleep behaviour disorder, this paralysis does not occur, and they may physically respond to their dreams.

The brain waves during REM sleep are mixed-frequency, and this is likely due to the dreams occurring during this stage. Dreaming is associated with high brain activity, and the brain remains highly active throughout the entirety of sleep to facilitate memory and emotion processing, dreaming, and more.

The first REM sleep stage usually starts about 90 minutes after falling asleep, and it lasts for about 10 minutes. With each subsequent sleep cycle, the duration of REM sleep increases, lasting between 30 to 60 minutes at its longest.

The amount of REM sleep a person gets each night decreases with age, from about eight hours at birth to 45 minutes at age 70.

The brain is highly active during REM sleep

Sleep is composed of several different stages, each with distinct brain wave patterns. The two main phases are rapid eye movement (REM) sleep and non-REM (NREM) sleep.

REM sleep is characterised by darting movements of the eyes under closed eyelids. Brain waves during REM sleep are very similar to brain waves during wakefulness. The brain is highly active during REM sleep, and this is the period of sleep in which dreaming occurs. It is also associated with the paralysis of muscle systems in the body, except for those that make circulation and respiration possible.

The brain waves associated with REM sleep are called beta waves. These are the fastest brain waves, with a frequency of 15–60 Hz. Beta waves are the most common daytime brain waves and are associated with engaging activities such as problem-solving and other cognitive tasks.

In addition to beta waves, theta waves are also observed during REM sleep. Theta waves are associated with deep states of meditation and are linked to implicit learning, information processing, and memory formation.

REM sleep is associated with the consolidation of emotional memories

Research has shown that sleep plays a critical role in memory processing, and that sleep, and its varied stages, contribute to latent processes of both declarative and procedural memory consolidation. Memory can be facilitated by emotion, leading to enhanced consolidation across increasing time delays. Sleep also facilitates offline memory processing, resulting in superior recall the next day.

REM sleep is believed to foster the memory consolidation of emotional events. Emotional arousal helps to memorize pictures, and the better consolidation of negative pictures compared to neutral ones was most pronounced in the SWS-deprived group, where a normal amount of REM sleep was present. This emotional memory bias correlated with REM sleep only in the SWS-deprived group.

The extent of emotional memory facilitation was significantly correlated with the amount of REM sleep and also with right-dominant prefrontal theta power during REM. The right-sided association between theta power and emotional memory improvement was also evident when examining each electrode independently.

However, the role of REM sleep in emotional memory consolidation is not yet fully understood. Some studies have failed to establish associations between REM sleep physiology and emotional memory performance.

REM sleep may be involved in emotional processing and regulation

Sleep is composed of several different stages that can be differentiated from one another by the patterns of brain wave activity that occur during each stage. Sleep can be divided into two different general phases: REM sleep and non-REM (NREM) sleep. REM sleep is marked by rapid movements of the eyes under closed eyelids. Brain waves during REM sleep appear very similar to brain waves during wakefulness.

REM sleep has been implicated in various aspects of learning and memory. Research has shown that REM sleep may be involved in emotional processing and regulation. In such instances, REM rebound may actually represent an adaptive response to stress in nondepressed individuals by suppressing the emotional salience of aversive events that occurred in wakefulness.

REM sleep abnormalities have been implicated in several neuropsychiatric disorders including PTSD. A meta-analysis of PTSD studies using polysomnographic (PSG) prior to 2007 found increased density of eye movements during REM sleep. In a prospective study in which hospitalized trauma victims were given PSG recordings within a month of trauma exposure, fragmented REM sleep patterns were found in patients who developed PTSD compared with resilient patients.

Neural activity at theta frequencies has been implicated in learning and memory with recent evidence of changes to REM theta power following fear conditioning. In a rodent model, enhanced activity and synchronization between the hippocampus and amygdala occurred at theta frequencies during REM sleep.

REM sleep is associated with consolidation and possibly further processing of affective components of memory. Its role in PTSD remains not well understood. Given the evidence that REM sleep can have an adaptive role in emotional memory processing and that this role is impaired among those with PTSD and the critical role for activity linked to theta frequencies, researchers sought to determine whether there is a difference in relative theta power during REM sleep in trauma-exposed individuals with PTSD versus resilience.

The findings of the study support the possibility that right frontal theta activity during REM sleep distinguishes resilient individuals from those with PTSD, supporting the possibility that it is a marker of affective memory processing capacities.

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