Editing Sleep (section)

=== Dreaming ===
{{Main|Dream}}
[[File:Glimpse of a dream (9391068364).jpg|thumb|Dreams often feel like waking life, yet with added surrealism.]]During sleep, especially REM sleep, humans tend to experience dreams. These are elusive and mostly unpredictable first-person experiences which seem logical and realistic to the dreamer while they are in progress, despite their frequently bizarre, irrational, and/or surreal qualities that become apparent when assessed after waking. Dreams often seamlessly incorporate concepts, situations, people, and objects within a person's mind that would not normally go together. They can include apparent sensations of all types, especially vision and movement.<ref name=HobsonEtAl2000>J. Alan Hobson, Edward F. Pace-Scott, & Robert Stickgold (2000), "Dreaming and the brain: Toward a cognitive neuroscience of conscious states", ''Behavioral and Brain Sciences'' 23.</ref>

Dreams tend to rapidly fade from memory after waking. Some people choose to keep a [[dream journal]], which they believe helps them build dream recall and facilitate the ability to experience [[lucid dreams]].

A lucid dream is a type of dream in which the dreamer becomes aware that they are dreaming while dreaming. In a preliminary study, dreamers were able to consciously [[Lucid dream#Two-way communication|communicate]] with experimenters via eye movements or facial muscle signals, and were able to comprehend complex questions and use working memory.<ref name="10.1016/j.cub.2021.01.026">{{cite journal|display-authors=3 |last1=Konkoly |first1=Karen R. |last2=Appel |first2=Kristoffer |last3=Chabani |first3=Emma |last4=Mangiaruga |first4=Anastasia |last5=Gott |first5=Jarrod |last6=Mallett |first6=Remington |last7=Caughran |first7=Bruce |last8=Witkowski |first8=Sarah |last9=Whitmore |first9=Nathan W. |last10=Mazurek |first10=Christopher Y. |last11=Berent |first11=Jonathan B. |last12=Weber |first12=Frederik D. |last13=Türker |first13=Başak |last14=Leu-Semenescu |first14=Smaranda |last15=Maranci |first15=Jean-Baptiste |last16=Pipa |first16=Gordon |last17=Arnulf |first17=Isabelle |last18=Oudiette |first18=Delphine |last19=Dresler |first19=Martin |last20=Paller |first20=Ken A. |title=Real-time dialogue between experimenters and dreamers during REM sleep |journal=Current Biology |date=18 February 2021 |volume=31 |issue=7 |pages=1417–1427.e6 |doi=10.1016/j.cub.2021.01.026 |pmid=33607035 |pmc=8162929 |language=English |issn=0960-9822|doi-access=free |bibcode=2021CBio...31E1417K }} [[File:CC-BY icon.svg|50px]] Available under [https://creativecommons.org/licenses/by/4.0/ CC BY 4.0] {{Webarchive|url=https://web.archive.org/web/20171016050101/https://creativecommons.org/licenses/by/4.0/ |date=16 October 2017 }}.</ref>

People have proposed many [[hypotheses]] about the functions of dreaming. [[Sigmund Freud]] postulated that dreams are the symbolic expression of frustrated desires that have been relegated to the [[unconscious mind]], and he used [[dream interpretation]] in the form of [[psychoanalysis]] in attempting to uncover these desires.<ref>See Freud: ''[[The Interpretation of Dreams]]''.</ref>

Counterintuitively, [[nocturnal penile tumescence|penile erections during sleep]] are not more frequent during sexual dreams than during other dreams.<ref>{{cite book| vauthors = Pinel JP |title=Biopsychology, 8th Edition|year=2011|publisher=Pearson Education, Inc.|isbn=978-0-205-83256-9|page=359}}</ref> The [[parasympathetic nervous system]] experiences increased activity during REM sleep which may cause erection of the penis or clitoris. In males, 80% to 95% of REM sleep is normally accompanied by partial to full penile erection, while only about 12% of men's dreams contain sexual content.<ref name="Saladin 2012 537">{{cite book| vauthors = Saladin KS |title=Anatomy and Physiology: The Unity of Form and Function|edition=6th|year=2012|publisher=McGraw-Hill|isbn=978-0-07-337825-1|page=537}}</ref>