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Rapid eye movement sleep

Physiology: – REM sleep is characterized by rapid eye movements and low muscle tone. – REM sleep is also known as paradoxical sleep due to […]

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Physiology:
– REM sleep is characterized by rapid eye movements and low muscle tone.
– REM sleep is also known as paradoxical sleep due to similarities with wakefulness.
– During REM sleep, brain activity resembles wakefulness with fast, desynchronized brainwaves.
– Theta rhythm in the hippocampus and gamma waves in the cortex are observed during REM sleep.
– Brain energy use in REM sleep equals or exceeds waking levels.

Electrical activity in the brain:
– EEG during REM sleep shows fast, low amplitude, desynchronized neural oscillations.
– Theta wave activity predominates in the hippocampus and cortex during REM sleep.
– Connectivity among brain regions differs in REM sleep compared to wakefulness.
– Brain energy use in REM sleep equals or exceeds waking levels.
– Frontal and posterior brain areas show different coherence levels during REM sleep.

Brain stem:
– REM sleep neural activity originates in the brain stem, especially the pontine tegmentum.
– REM sleep is preceded by PGO waves originating in the brain stem.
– PGO waves cause rapid eye movements in REM sleep.
– PGO waves occur in clusters every 6 seconds during the transition to REM sleep.
– PGO waves exhibit high amplitude in the visual cortex.

Forebrain:
– PET scans show limbic and paralimbic systems are more activated during REM sleep.
– Areas activated during REM sleep are inversely related to non-REM sleep.
– The anterior paralimbic REM activation area is linked to emotion, memory, fear, and sex.
– Superior frontal gyrus, medial frontal areas, and other regions show equal activity in REM sleep as in wakefulness.
– The amygdala is active during REM sleep and may contribute to generating PGO waves.

Rapid eye movement sleep (Wikipedia)

Rapid eye movement sleep (REM sleep or REMS) is a unique phase of sleep in mammals (including humans) and birds, characterized by random rapid movement of the eyes, accompanied by low muscle tone throughout the body, and the propensity of the sleeper to dream vividly.

A sample hypnogram (electroencephalogram of sleep) showing sleep cycles characterized by increasing paradoxical (REM) sleep
EEG of a mouse that shows REM sleep being characterized by prominent theta-rhythm

The REM phase is also known as paradoxical sleep (PS) and sometimes desynchronized sleep or dreamy sleep, because of physiological similarities to waking states including rapid, low-voltage desynchronized brain waves. Electrical and chemical activity regulating this phase seem to originate in the brain stem, and is characterized most notably by an abundance of the neurotransmitter acetylcholine, combined with a nearly complete absence of monoamine neurotransmitters histamine, serotonin and norepinephrine. Experiences of REM sleep are not transferred to permanent memory due to absence of norepinephrine.

REM sleep is physiologically different from the other phases of sleep, which are collectively referred to as non-REM sleep (NREM sleep, NREMS, synchronized sleep). The absence of visual and auditory stimulation (sensory deprivation) during REM sleep can cause hallucinations.[failed verification] REM and non-REM sleep alternate within one sleep cycle, which lasts about 90 minutes in adult humans. As sleep cycles continue, they shift towards a higher proportion of REM sleep. The transition to REM sleep brings marked physical changes, beginning with electrical bursts called "ponto-geniculo-occipital waves" (PGO waves) originating in the brain stem. REM sleep occurs 4 times in a 7-hour sleep. Organisms in REM sleep suspend central homeostasis, allowing large fluctuations in respiration, thermoregulation and circulation which do not occur in any other modes of sleeping or waking. The body abruptly loses muscle tone, a state known as REM atonia.

In 1953, Professor Nathaniel Kleitman and his student Eugene Aserinsky defined rapid eye movement and linked it to dreams. REM sleep was further described by researchers, including William Dement and Michel Jouvet. Many experiments have involved awakening test subjects whenever they begin to enter the REM phase, thereby producing a state known as REM deprivation. Subjects allowed to sleep normally again usually experience a modest REM rebound. Techniques of neurosurgery, chemical injection, electroencephalography, positron emission tomography, and reports of dreamers upon waking have all been used to study this phase of sleep.

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