Editing Sleep and learning (section)

==Increased learning==
Popular sayings can reflect the notion that remolded memories produce new creative associations in the morning, and that performance often improves after a time-interval that includes sleep.<ref>{{cite news| last=Neal | first=Rome | title=Sleep On It | website=CBS News | date=21 January 2004 | url=https://www.cbsnews.com/news/sleep-on-it/ | access-date=29 September 2018}}</ref> Current studies demonstrate that a healthy sleep produces a significant [[learning]]-dependent performance boost.<ref>{{cite web | title=The Role of Sleep in Memory, Learning, and Health | website=Therapeutic Literacy Center | date=25 February 2014 | url=https://therapeuticliteracycenter.com/the-role-of-sleep-in-learning-memory-and-health/ | access-date=29 September 2018 |author=Maria Bagby}}</ref><ref>{{cite news |title=To understand the big picture, give it time – and sleep |date=20 April 2007 |url=http://www.eurekalert.org/pub_releases/2007-04/bidm-tut042007.php |work=EurekAlert |access-date=23 April 2007}}</ref> The idea is that sleep helps the brain to edit its memory, looking for important patterns and extracting overarching rules which could be described as 'the gist', and integrating this with existing memory.<ref>{{cite journal | last1=Stickgold | first1=Robert | last2=Walker | first2=Matthew P | title=Sleep-dependent memory triage: evolving generalization through selective processing | journal=Nature Neuroscience | volume=16 | issue=2 | pages=139–145 | date=28 January 2013 | issn=1546-1726 | doi=10.1038/nn.3303 | pmid=23354387 | pmc=5826623 }}</ref>  The 'synaptic scaling' hypothesis suggests that sleep plays an important role in regulating learning that has taken place while awake, enabling more efficient and effective storage in the brain, making better use of space and energy.<ref name="smrv-journal.com">{{cite journal | last1=Tononi | first1=Giulio | last2=Cirelli | first2=Chiara | title=Sleep function and synaptic homeostasis | journal=Sleep Medicine Reviews | volume=10 | issue=1 | date=1 January 2006 | issn=1087-0792 | pmid=16376591 | doi=10.1016/j.smrv.2005.05.002 | pages=49–62 | s2cid=16129740 }}</ref>

Healthy sleep must include the appropriate sequence and proportion of [[NREM]] and [[REM phase]]s, which play different roles in the memory consolidation-optimization process. During a normal night of sleep, a person will alternate between periods of NREM and REM sleep. Each cycle is approximately 90 minutes long, containing a 20-30 minute bout of REM sleep.<ref name="Carlson, N. R. 2010">{{cite book|last=Carlson|first=Neil R.|title=Physiology of Behavior|edition=11th|year=2010|publisher=Allyn & Bacon|location=New York}}</ref> NREM sleep consists of sleep stages 1–4, and is where movement can be observed.  A person can still move their body when they are in NREM sleep. If someone sleeping turns, tosses, or rolls over, this indicates that they are in NREM sleep. REM sleep is characterized by the lack of muscle activity. Physiological studies have shown that aside from the occasional twitch, a person actually becomes paralyzed during REM sleep.<ref name="Carlson, N. R. 2010"/>  In [[motor skill]] learning, an interval of sleep may be critical for the expression of performance gains; without sleep these gains will be delayed.<ref>{{cite journal | last1=Korman | first1=Maria | last2=Raz | first2=Naftali | last3=Flash | first3=Tamar|author3-link=Tamar Flash | last4=Karni | first4=Avi | title=Multiple shifts in the representation of a motor sequence during the acquisition of skilled performance | journal=Proceedings of the National Academy of Sciences | volume=100 | issue=21 | date=14 October 2003 | issn=0027-8424 | pmid=14530407 | doi=10.1073/pnas.2035019100 | pages=12492–12497 |pmc=218785| bibcode=2003PNAS..10012492K | doi-access=free }}</ref>

Procedural memories are a form of nondeclarative memory, so they would most benefit from the fast-wave REM sleep.<ref name="Carlson, N. R. 2010"/> In a study,<ref>Walker, M.P. (5 October 2009). *Sleep and Cognition II: Memory (Procedural [Skills]).* Lecture given in Psychology 133 at the University of California, Berkeley, CA.</ref> [[Procedural memory|procedural memories]] have been shown to benefit from sleep.<ref>{{cite journal | last1=Walker | first1=Matthew P. | last2=Brakefield | first2=Tiffany | last3=Morgan | first3=Alexandra | last4=Hobson | first4=J.Allan | last5=Stickgold | first5=Robert | title=Practice with Sleep Makes Perfect | journal=Neuron | publisher=Elsevier BV | volume=35 | issue=1 | year=2002 | issn=0896-6273 | doi=10.1016/s0896-6273(02)00746-8 | pmid=12123620 | pages=205–211| doi-access=free }}</ref>    Subjects were tested using a tapping task, where they used their fingers to tap a specific sequence of numbers on a keyboard, and their performances were measured by accuracy and speed. This finger-tapping task was used to simulate learning a motor skill. The first group was tested, retested 12 hours later while awake, and finally tested another 12 hours later with sleep in between. The other group was tested, retested 12 hours later with sleep in between, and then retested 12 hours later while awake. The results showed that in both groups, there was only a slight improvement after a 12-hour wake session, but a significant increase in performance after each group slept. This study gives evidence that REM sleep is a significant factor in consolidating motor skill procedural memories, therefore sleep deprivation can impair performance on a motor learning task.  This memory decrement results specifically from the loss of stage 2, REM sleep.<ref>{{cite journal | last1=Walker | first1=Matthew P. | last2=Stickgold | first2=Robert | title=Sleep-Dependent Learning and Memory Consolidation | journal=Neuron | publisher=Elsevier BV | volume=44 | issue=1 | year=2004 | issn=0896-6273 | doi=10.1016/j.neuron.2004.08.031 | pages=121–133| pmid=15450165 | doi-access=free }}</ref>

[[Declarative memory]] has also been shown to benefit from sleep, but not in the same way as procedural memory. Declarative memories benefit from the slow-waves nREM sleep.<ref name="Carlson, N. R. 2010"/> A study<ref>Walker, M.P. (7 October 2009). *Sleep and Cognition III: Memory (Declarative [Facts]).* Lecture given in Psychology 133 at the University of California, Berkeley, CA.</ref> was conducted where the subjects learned word pairs, and the results showed that sleep not only prevents the decay of memory, but also actively fixates declarative memories.<ref>{{cite journal | last1=Payne | first1=Jessica D. | last2=Tucker | first2=Matthew A. | last3=Ellenbogen | first3=Jeffrey M. | last4=Wamsley | first4=Erin J. | last5=Walker | first5=Matthew P. | last6=Schacter | first6=Daniel L. | last7=Stickgold | first7=Robert | editor-last=Mazza | editor-first=Marianna | title=Memory for Semantically Related and Unrelated Declarative Information: The Benefit of Sleep, the Cost of Wake | journal=PLOS ONE | publisher=Public Library of Science (PLoS) | volume=7 | issue=3 | date=22 March 2012 | issn=1932-6203 | doi=10.1371/journal.pone.0033079 | page=e33079 | display-authors=5| pmid=22457736 | pmc=3310860| bibcode=2012PLoSO...733079P | doi-access=free }}</ref> Two of the groups learned word pairs, then either slept or stayed awake, and were tested again. The other two groups did the same thing, except they also learned interference pairs right before being retested to try to disrupt the previously learned word pairs. The results showed that sleep was of ''some'' help in retaining the word pair associations, while against the interference pair, sleep helped ''significantly''.

After sleep, there is increased insight.  This is because sleep helps people to reanalyze their memories. The same patterns of brain activity that occur during learning have been found to occur again during sleep, only faster. One way that sleep strengthens memories is by weeding out the less successful connections between neurons in the brain.  This weeding out is essential to prevent overactivity.  The brain compensates for strengthening some synapses (connections) between neurons, by weakening others.  The weakening process occurs mostly during sleep. This weakening during sleep allows for strengthening of other connections while we are awake. Learning is the process of strengthening connections, therefore this process could be a major explanation for the benefits that sleep has on memory.<ref>{{cite book|last=Kalat|first=James W.|title=Biological Psychology|edition=10th|year=2009|publisher=Wadsworth|location=California}}</ref>

Research has shown that taking an afternoon nap increases learning capacity. A study <ref>{{cite journal | last1=Cai | first1=Denise J. | last2=Mednick | first2=Sarnoff A. | last3=Harrison | first3=Elizabeth M. | last4=Kanady | first4=Jennifer C. | last5=Mednick | first5=Sara C. | title=REM, not incubation, improves creativity by priming associative networks | journal=Proceedings of the National Academy of Sciences | volume=106 | issue=25 | date=23 June 2009 | issn=0027-8424 | pmid=19506253 | doi=10.1073/pnas.0900271106 | pages=10130–10134 |pmc=2700890| bibcode=2009PNAS..10610130C | doi-access=free }}</ref> tested two groups of subjects on a nondeclarative memory task. One group engaged in REM sleep, and one group did not (meaning that they engaged in NREM sleep). The investigators found that the subjects who engaged only in NREM sleep did not show much improvement. The subjects who engaged in REM sleep performed significantly better, indicating that REM sleep facilitated the consolidation of nondeclarative memories.<ref name="Carlson, N. R. 2010" />  A more recent study<ref>{{cite journal | last1=Holz | first1=Johannes | last2=Piosczyk | first2=Hannah | last3=Landmann | first3=Nina | last4=Feige | first4=Bernd | last5=Spiegelhalder | first5=Kai | last6=Riemann | first6=Dieter | last7=Nissen | first7=Christoph | last8=Voderholzer | first8=Ulrich | editor-last=Schmidt | editor-first=Ulrike | title=The Timing of Learning before Night-Time Sleep Differentially Affects Declarative and Procedural Long-Term Memory Consolidation in Adolescents | journal=PLOS ONE | publisher=Public Library of Science (PLoS) | volume=7 | issue=7 | date=12 July 2012 | issn=1932-6203 | doi=10.1371/journal.pone.0040963 | pmid=22808287 | pmc=3395672 | page=e40963 | bibcode=2012PLoSO...740963H |display-authors=5| doi-access=free }}</ref> demonstrated that a procedural task was learned and retained better if it was encountered immediately before going to sleep, while a declarative task was learned better in the afternoon.<ref name="smrv-journal.com"/>