Eeg Activity During Rem Sleep: A Visual Guide

Electroencephalography (EEG) is a non-invasive and painless method of measuring brain activity through electrical activity recordings at the scalp. It is used to study sleep, and the EEG activity during REM sleep is quite distinct from that of non-REM sleep. REM sleep is characterised by rapid eye movement, low muscle tone, and vivid dreams. The EEG trace during this stage shows low-amplitude events at a high frequency, resembling the pattern observed during wakefulness. This is in contrast to the deep, slow-wave sleep of non-REM, which is marked by large-amplitude, low-frequency events.

Low-voltage, fast brain waves

During REM sleep, EEG recordings show low-voltage, fast brain waves. This means that the brain waves are of low amplitude and high frequency. This pattern of brain activity is similar to that observed in a person who is awake.

REM sleep is characterised by random rapid movement of the eyes, low muscle tone throughout the body, and the likelihood of the sleeper to dream vividly. The brain acts as if it is somewhat awake, with cerebral neurons firing with the same overall intensity as in wakefulness. However, the body is paralysed during REM sleep.

The transition to REM sleep is marked by electrical bursts called ponto-geniculo-occipital waves (PGO waves) originating in the brain stem. The eye movements during REM sleep follow these PGO waves, which exhibit their highest amplitude upon moving into the visual cortex.

The brain waves during REM sleep are fast, low-amplitude, desynchronized neural oscillations (brain waves) that resemble the pattern seen during wakefulness. This is in contrast to the slow delta waves pattern of NREM deep sleep. An important element of this contrast is the 3–10 Hz theta rhythm in the hippocampus and 40–60 Hz gamma waves in the cortex.

During REM sleep, the brain exhibits greater activation in areas linked with emotion, memory, fear, and sex, which may relate to the experience of dreaming. The brain's energy use in REM sleep, as measured by oxygen and glucose metabolism, equals or exceeds that of a waking brain.

REM sleep is also known as paradoxical sleep due to its similarities to wakefulness.

Similar to wakefulness

During REM sleep, the brain's electrical activity is very similar to that of a person who is awake. This is why REM sleep is sometimes referred to as "paradoxical sleep".

REM sleep is characterised by fast, low-amplitude, desynchronised neural oscillation (brainwaves) that resemble the pattern seen during wakefulness. The brainwaves during REM sleep differ from the slow delta waves that are typical of NREM deep sleep. An important element of this contrast is the presence of a 3–10 Hz theta rhythm in the hippocampus and 40–60 Hz gamma waves in the cortex. These EEG activity rhythms are also observed during wakefulness.

The cortical and thalamic neurons in the waking and REM sleeping brain are more depolarised (fire more readily) than in the NREM deep sleeping brain. Human theta wave activity predominates during REM sleep in both the hippocampus and the cortex.

During REM sleep, electrical connectivity among different parts of the brain manifests differently than during wakefulness. Frontal and posterior areas are less coherent in most frequencies, which has been linked to the chaotic experience of dreaming. However, the posterior areas are more coherent with each other, as are the right and left hemispheres of the brain, especially during lucid dreams.

Brain energy use in REM sleep, as measured by oxygen and glucose metabolism, equals or exceeds energy use when awake. The rate in non-REM sleep is 11–40% lower.

The superior frontal gyrus, medial frontal areas, intraparietal sulcus, and superior parietal cortex, areas involved in sophisticated mental activity, show equal activity in REM sleep as in wakefulness. The amygdala is also active during REM sleep and may participate in generating the PGO waves that are a feature of REM sleep.

During REM sleep, the brain waves associated with this stage of sleep are very similar to those observed when a person is awake. This is the period of sleep in which dreaming occurs. It is also associated with paralysis of muscle systems in the body, except for those that make circulation and respiration possible. Therefore, no movement of voluntary muscles occurs during REM sleep in a normal individual.

Theta waves

Theta activity during REM sleep may serve as a biomarker of the capacity for adaptive emotional memory processing among trauma-exposed individuals.

Sawtooth waves

The first occurrence of sawtooth waves during sleep typically happens during the electrographic stage II period before the beginning of REM sleep. This sequence of events includes a generalized body movement, followed by muscle tone reduction, the appearance of sawtooth waves, and ending with the first REM. The overall mean onset time of sawtooth waves is 378 seconds, with a range of 169-779 seconds.

Delta waves

The progression of sleep stages throughout the night follows a predictable pattern. Typically, a person will first enter NREM1 sleep, followed by NREM2, then NREM3, before transitioning back to NREM2 and NREM1. They may then enter REM sleep before cycling back through the stages to NREM3. As the night goes on, the amount of time spent in REM sleep increases, while the time spent in deep sleep decreases.

The function of delta waves and their role in sleep is not yet fully understood. However, it is known that sleep plays a crucial role in memory consolidation and cognitive performance. Sleep deprivation can have disastrous consequences, including an increased risk of accidents and negative effects on overall health and well-being.

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