Rem Sleep

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"The foundation for much of what we know about sleep was gathered approximately 40 years ago by researcher, Michel Jouvet. This French scientist studied the effects of gross brain lesions and brain transections on sleep behavior and related phenomena. It was Jouvet who first suggested that a brainstem region is responsible for the initiation of events that result in the stage of sleep called REM sleep. REM sleep is a stage associated with rapid eye movements, a high degree of brain wave activity, relaxation of large muscles of the body, and increased frequency of dreams. More about the stages of sleep and how REM sleep fits into this overall picture is discussed elsewhere.

REM sleep is initiated by high amplitude, low frequency (1 Hertz, 1 per second) monophasic electrical spike activity known as the PGO wave (pons-geniculate-occipital). This electrical spike begins in the pons, spreading next to the lateral geniculate nucleus of the thalamus and then, finally, to the occipital cortex. PGO waves typically precede the onset of REM sleep and continue throughout this stage. They are synchronized with the lateral eye movements that occur during REM sleep.

The loss of REM sleep due to sleep deprivation is known to cause a rebound, during which the amount of time spent in this stage of sleep is increased until the loss is compensated for. This rebound phenomenon appears to be linked most closely with PGO wave activity. Following REM sleep deprivation, animals show PGO waves during stages 2 - 4 of sleep when they don't normally occur. They may even show up while the animal is awake and occur in association with bizarre behaviors suggesting that the animal is hallucinating.

In addition to dreaming, a number of other behavioral phenomena occur during REM sleep. An organism is more alert to its surroundings during REM sleep than during other stages of sleep. The incorporation of new memories from the day's events into long term memory (memory consolidation) may occur...
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