Miya Pearson
Sleep is composed of several stages, including rapid eye movement (REM) sleep, which is characterised by darting movements of the eyes under closed eyelids. Brain waves during REM sleep are similar to those during wakefulness.
REM sleep is associated with distinct global cortical dynamics and is controlled by the occipital cortex. Brain activity during REM sleep is dominated by the cortical activity pattern with higher activation in the occipital cortex and low activity in the somatic sensorimotor cortex.
Theta waves are slower brain waves that gradually replace alpha waves as a person transitions from a relaxed state to being asleep. They are most commonly seen during the first stage of sleep, which is the lightest sleep stage. They may also be seen during the second stage of sleep.
Theta frequency activity during REM sleep is greater in people with resilience versus post-traumatic stress disorder (PTSD).
| Characteristics | Values |
|---|---|
| Brain waves | Beta waves, Sleep spindles, K-complexes, Theta waves, Delta waves |
| Beta waves | Faster waves, the most common brain waves |
| Sleep spindles | Occur during the second stage of sleep |
| K-complexes | Sharp waves, last at least half a second |
| Theta waves | Slower brain waves, occur during the first and second stage of sleep |
| Delta waves | The slowest brain waves, occur during the third stage of sleep |
What You'll Learn
Brain waves during REM sleep
Sleep is divided into two distinct phases: REM (rapid eye movement) sleep and non-REM sleep. Each phase is characterised by unique brain wave patterns.
During REM sleep, the brain exhibits fast, tonic, and unsynchronised brain activity. This brain wave pattern is similar to the brain activity observed in wakeful individuals. REM sleep is also characterised by darting eye movements and muscle paralysis, except for the muscles that enable circulation and respiration. Dreaming occurs during this stage of sleep.
In contrast, non-REM sleep is marked by slow, synchronous delta waves, spindles, and isolated negative deflections. Non-REM sleep is further divided into three stages, each with distinct brain wave patterns.
The first stage of non-REM sleep is a transitional phase between wakefulness and sleep. During this stage, the brain exhibits alpha and theta waves. Alpha waves are low-frequency, high-amplitude brain waves that are associated with a state of relaxation. As an individual progresses through the first stage of sleep, theta wave activity increases. Theta waves are low-frequency, high-amplitude brain waves.
In the second stage of non-REM sleep, the body enters a state of deep relaxation. The brain continues to exhibit theta waves, which are interrupted by sleep spindles—brief bursts of high-frequency brain waves that are important for learning and memory.
The third stage of non-REM sleep is often referred to as deep sleep or slow-wave sleep. This stage is characterised by delta waves, which are low-frequency, high-amplitude brain waves. It is difficult to wake someone during this stage of sleep.
Throughout the night, individuals cycle through the stages of non-REM and REM sleep multiple times. The amount of REM sleep decreases with age, from about 8 hours at birth to around 45 minutes at age 70.
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Theta waves during REM sleep
Theta waves are a characteristic of hippocampal activity during both active exploratory behaviour and REM sleep. Theta waves during REM sleep have been linked to the processing of emotional memory traces. Theta waves during REM sleep are thought to drive the emotionally modulated processing of novel memory traces within the hippocampus. Theta waves during REM sleep may also mediate the integration of novel memory traces within the neocortex.
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REM sleep and memory consolidation
REM sleep has been linked to memory consolidation, with some studies suggesting that it is important for the consolidation of certain types of memory, such as procedural memory. However, the evidence for this hypothesis is weak and contradictory.
Human Studies
Human studies investigating the link between REM sleep and memory consolidation have produced mixed results. Some studies have found no change in REM sleep time after learning, while others have reported an increase in REM sleep density or duration. It is difficult to draw conclusions from these studies due to factors such as small sample sizes and the challenge of devising proper control groups.
Furthermore, studies correlating REM sleep parameters with learning ability in humans have yielded inconsistent results. While some studies suggest a link between REM sleep and intelligence, others found no correlation between REM sleep duration and intelligence in normal populations.
Animal Studies
Animal studies examining the link between REM sleep and memory consolidation have also produced conflicting results. Some studies reported that REM sleep deprivation blocked consolidation, while others found no effect or even improved consolidation. The interpretation of these findings is complicated by the use of different deprivation techniques, such as the platform technique, which may introduce stress and other confounding factors.
Pharmacological and Lesion Studies
Pharmacological and brain lesion-induced suppression of REM sleep in humans generally do not result in memory deficits, providing further evidence against a critical role for REM sleep in memory consolidation. For example, the use of monoamine oxidase (MAO) inhibitors, which can completely suppress REM sleep, has not been associated with memory impairment. On the other hand, benzodiazepines, which do not significantly affect REM sleep, have been found to have deleterious effects on memory.
Neurochemical Changes
The neurochemical changes during REM sleep may also provide insights into its role in memory consolidation. The cessation of norepinephrine release during REM sleep, for example, has been linked to reduced expression of proteins associated with synaptic plasticity.
Non-REM Sleep and Memory Consolidation
While most research has focused on the role of REM sleep in memory consolidation, some studies have suggested that non-REM sleep may also be important. Synchronous discharge in the hippocampus and neocortex during non-REM sleep, for instance, has been implicated in reinforcing synaptic connections. However, more research is needed to understand the specific role of non-REM sleep in memory consolidation.
In conclusion, while sleep is crucial for optimal acquisition and performance of learned tasks, the existing evidence does not strongly support a major role for REM sleep in memory consolidation.
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REM sleep and emotional processing
REM sleep is associated with the processing of emotions and emotional memories. It is thought to play a role in emotional regulation and memory consolidation. REM sleep suppression has been found to increase general negative affect and amygdala responses to social exclusion.
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REM sleep and regulation of sleep-wake states
Sleep is composed of several different stages, each with its own unique patterns of brain wave activity. These stages can be broadly divided into two types: rapid eye movement (REM) sleep and non-rapid eye movement (NREM) sleep. During REM sleep, the eyes move rapidly in different directions, and brain activity is similar to that observed during wakefulness. Dreaming typically occurs during this stage. On the other hand, NREM sleep is characterised by slower brain activity, and the body enters a state of deep relaxation.
REM sleep is believed to play a crucial role in the regulation of sleep-wake states. It is associated with the processing of emotional experiences and the consolidation of memory. During this stage, the brain repairs itself, strengthens neural connections, and transfers short-term memories into long-term storage. The first REM cycle of the night is usually the shortest, lasting around 10 minutes, while subsequent cycles can last up to an hour.
The regulation of sleep-wake states is also influenced by the preceding stages of NREM sleep. NREM sleep is typically divided into three stages, with each stage marked by distinct patterns of brain activity. During the first stage, the body transitions from wakefulness to sleep, characterised by a decrease in muscle tension, heart rate, and body temperature. In the second stage, the body enters a deeper state of relaxation, with further reductions in heart rate and breathing. The third stage of NREM sleep is the deepest, during which the body repairs tissues, builds muscle and bone, and strengthens the immune system.
The progression through these sleep stages follows a cyclical pattern, with each cycle lasting between 90 and 120 minutes. Typically, an individual will experience four to six of these cycles throughout the night. The duration and composition of each cycle can vary depending on factors such as age, recent sleep patterns, and alcohol consumption.
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Frequently asked questions
Brain waves during REM sleep are very similar to brain waves during wakefulness. They are characterised by tonic, fast, unsynchronized activity. Brain waves during REM sleep include theta waves, beta waves, sleep spindles, K-complexes, and delta waves.
Non-REM sleep is characterised by slow, synchronous delta waves, spindles, and isolated negative deflections. Brain waves during non-REM sleep include theta waves, beta waves, sleep spindles, K-complexes, and delta waves.
The main difference between REM and non-REM sleep is that REM sleep is associated with dreaming and is characterised by rapid eye movements. Non-REM sleep is further divided into four stages, with the first being a transitional phase between wakefulness and sleep.
