Editing Rapid eye movement sleep (section)

=== Muscle ===

'''REM atonia''', an almost complete paralysis of the body, is accomplished through the inhibition of [[motor neurons]]. When the body shifts into REM sleep, motor neurons throughout the body undergo a process called [[hyperpolarization (biology)|hyperpolarization]]:<ref>{{cite journal | vauthors = Brooks PL, Peever JH | title = Unraveling the mechanisms of REM sleep atonia | journal = Sleep | volume = 31 | issue = 11 | pages = 1492–1497 | date = November 2008 | pmid = 19226735 | pmc = 2579970 | doi = 10.1093/sleep/31.11.1492 }}</ref> their already-negative [[membrane potential]] decreases by another 2–10 [[Volt|millivolts]], thereby raising the threshold which a stimulus must overcome to excite them. Muscle inhibition may result from unavailability of monoamine neurotransmitters (restraining the abundance of acetylcholine in the brainstem) and perhaps from mechanisms used in waking muscle inhibition.<ref name="Steriade_2013" />{{rp|§10.8–9.1 309–324}} The [[medulla oblongata]], located between pons and spine, seems to have the capacity for organism-wide muscle inhibition.<ref name=LaiSiegel>{{cite book | vauthors = Lai YY, Siegel JM | date = 1999 | chapter = Muscle Atonia in REM Sleep | title = Rapid Eye Movement Sleep | publisher = CRC Press | veditors = Mallick BN, Inoué S | isbn = 978-0-8247-0322-6 }}</ref> Some localized twitching and reflexes can still occur.<ref name = "Parmeggiani_2011" />{{rp|17}} Pupils contract.<ref name=Siegel2009>{{cite journal | vauthors = Siegel JM | title = The neurobiology of sleep | journal = Seminars in Neurology | volume = 29 | issue = 4 | pages = 277–296 | date = September 2009 | pmid = 19742406 | pmc = 8809119 | doi = 10.1055/s-0029-1237118 }}</ref>

Lack of REM [[atonia]] causes [[REM behavior disorder]], where those affected physically act out their dreams,<ref name="pmid1620348">{{cite journal | vauthors = Lapierre O, Montplaisir J | title = Polysomnographic features of REM sleep behavior disorder: development of a scoring method | journal = Neurology | volume = 42 | issue = 7 | pages = 1371–1374 | date = July 1992 | pmid = 1620348 | doi = 10.1212/wnl.42.7.1371 | s2cid = 25312217 }}</ref> or conversely "dream out their acts", under an alternative theory on the relationship between muscle impulses during REM and associated mental imagery (which would also apply to people without the condition, except that commands to their muscles are suppressed).<ref name="Steriade_2013" />{{rp|§13.3.2.3 428–432}} This is different from conventional [[sleepwalking]], which takes place during slow-wave sleep, not REM.<ref name = "Jouvet_1999" />{{rp|102}} [[Narcolepsy]], by contrast, seems to involve excessive and unwanted REM atonia: [[cataplexy]] and [[excessive daytime sleepiness]] while awake, [[hypnagogic hallucinations]] before entering slow-wave sleep, or [[sleep paralysis]] while waking.<ref name="Steriade_2013" />{{rp|§13.1 396–400}} Other psychiatric disorders including depression have been linked to disproportionate REM sleep.<ref name="Steriade_2013" />{{rp|§13.2 400–415}} Patients with suspected sleep disorders are typically evaluated by [[polysomnogram]].<ref>{{cite journal | vauthors = Koval'zon VM | title = [Central mechanisms of sleep-wakefulness cycle] | journal = Fiziologiia Cheloveka | volume = 37 | issue = 4 | pages = 124–134 | date = Jul–Aug 2011 | pmid = 21950094 }}</ref><ref>{{cite web |title=Polysomnography |url= https://www.nlm.nih.gov/medlineplus/ency/article/003932.htm |access-date=2 November 2011 | work = Medline Plus | publisher = U.S. National Library of Medicine }}</ref>

Lesions of the pons to prevent atonia have induced functional "REM behavior disorder" in animals.<ref name = "Parmeggiani_2011" />{{rp|87}}