![]() ![]() ![]() As sleep cycles continue, they shift towards a higher proportion of REM sleep. REM and non-REM sleep alternate within one sleep cycle, which lasts about 90 minutes in adult humans. The absence of visual and auditory stimulation ( sensory deprivation) during REM sleep can cause hallucinations. 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). Experiences of REM sleep are not transferred to permanent memory due to absence of norepinephrine. Electrical and chemical activity regulating this phase seems 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. 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. Rapid eye movement sleep ( REM sleep or REMS) is a unique phase of sleep in humans, mammals 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. EEG of a mouse that shows REM sleep being characterized by prominent theta-rhythm ![]() Phase of sleep characterized by random & rapid eye movements A sample hypnogram (electroencephalogram of sleep) showing sleep cycles characterized by increasing paradoxical (REM) sleep. ![]()
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