Editing Sleep (section)

=== Memory processing ===
{{Further|Sleep and memory|Neuroscience of sleep|Sleep and learning|Page 4=Neuroscience of sleep}}

It has been widely accepted that sleep must support the formation of long-term memory, and generally increasing previous learning and experiences recalls. However, its benefit seems to depend on the phase of sleep and the type of memory.<ref>{{cite journal | vauthors = Plihal W, Born J | title = Effects of early and late nocturnal sleep on declarative and procedural memory | journal = Journal of Cognitive Neuroscience | volume = 9 | issue = 4 | pages = 534–47 | date = July 1997 | pmid = 23968216 | doi = 10.1162/jocn.1997.9.4.534 | s2cid = 3300300 }}</ref> For example, declarative and procedural memory-recall tasks applied over early and late nocturnal sleep, as well as wakefulness controlled conditions, have been shown that declarative memory improves more during early sleep (dominated by SWS) while procedural memory during late sleep (dominated by REM sleep) does so.<ref name=":02">{{cite journal | vauthors = Rasch B, Büchel C, Gais S, Born J | title = Odor cues during slow-wave sleep prompt declarative memory consolidation | journal = Science | volume = 315 | issue = 5817 | pages = 1426–9 | date = March 2007 | pmid = 17347444 | doi = 10.1126/science.1138581 | s2cid = 19788434 | bibcode = 2007Sci...315.1426R }}</ref><ref name=":13">{{cite journal | vauthors = Born J, Wilhelm I | title = System consolidation of memory during sleep | journal = Psychological Research | volume = 76 | issue = 2 | pages = 192–203 | date = March 2012 | pmid = 21541757 | pmc = 3278619 | doi = 10.1007/s00426-011-0335-6 }}</ref>

With regard to declarative memory, the functional role of SWS has been associated with hippocampal replays of previously encoded neural patterns that seem to facilitate long-term memory consolidation.<ref name=":02" /><ref name=":13" /> This assumption is based on the active system consolidation hypothesis, which states that repeated reactivations of newly encoded information in the hippocampus during slow oscillations in NREM sleep mediate the stabilization and gradual integration of declarative memory with pre-existing knowledge networks on the cortical level.<ref>{{cite journal | vauthors = Diekelmann S, Born J | title = The memory function of sleep | journal = Nature Reviews. Neuroscience | volume = 11 | issue = 2 | pages = 114–26 | date = February 2010 | pmid = 20046194 | doi = 10.1038/nrn2762 | s2cid = 1851910 }}</ref> It assumes the hippocampus might hold information only temporarily and in a fast-learning rate, whereas the neocortex is related to long-term storage and a slow-learning rate.<ref name=":02" /><ref name=":13" /><ref name=":1">{{cite journal | vauthors = Rasch B, Born J | title = About sleep's role in memory | journal = Physiological Reviews | volume = 93 | issue = 2 | pages = 681–766 | date = April 2013 | pmid = 23589831 | pmc = 3768102 | doi = 10.1152/physrev.00032.2012 }}</ref><ref name=":22">{{cite journal | vauthors = Schreiner T, Rasch B | title = Boosting Vocabulary Learning by Verbal Cueing During Sleep | journal = Cerebral Cortex | volume = 25 | issue = 11 | pages = 4169–79 | date = November 2015 | pmid = 24962994 | doi = 10.1093/cercor/bhu139 | doi-access = free }}</ref><ref name=":52">{{cite journal | vauthors = Schreiner T, Rasch B | title = The beneficial role of memory reactivation for language learning during sleep: A review | journal = Brain and Language | volume = 167 | pages = 94–105 | date = April 2017 | pmid = 27036946 | doi = 10.1016/j.bandl.2016.02.005 | url = https://doc.rero.ch/record/323249/files/schreinerrasch2017_brainlang.pdf | s2cid = 3377186 }}</ref> This dialogue between the hippocampus and neocortex occurs in parallel with hippocampal [[Sharp waves and ripples|sharp-wave ripples]] and [[Sleep spindle|thalamo-cortical spindles]], synchrony that drives the formation of the spindle-ripple event which seems to be a prerequisite for the formation of long-term memories.<ref name=":13" /><ref name=":1" /><ref name=":52" /><ref name=":32">{{cite journal | vauthors = Ngo HV, Martinetz T, Born J, Mölle M | title = Auditory closed-loop stimulation of the sleep slow oscillation enhances memory | journal = Neuron | volume = 78 | issue = 3 | pages = 545–53 | date = May 2013 | pmid = 23583623 | doi = 10.1016/j.neuron.2013.03.006 | doi-access = free }}</ref>

Reactivation of memory also occurs during wakefulness and its function is associated with serving to update the reactivated memory with newly encoded information, whereas reactivations during SWS are presented as crucial for memory stabilization.<ref name=":13" /> Based on targeted memory reactivation (TMR) experiments that use associated memory cues to triggering memory traces during sleep, several studies have been reassuring the importance of nocturnal reactivations for the formation of persistent memories in neocortical networks, as well as highlighting the possibility of increasing people's memory performance at declarative recalls.<ref name=":02" /><ref name=":22" /><ref name=":52" /><ref name=":32" /><ref>{{cite journal | vauthors = Klinzing JG, Kugler S, Soekadar SR, Rasch B, Born J, Diekelmann S | title = Odor cueing during slow-wave sleep benefits memory independently of low cholinergic tone | journal = Psychopharmacology | volume = 235 | issue = 1 | pages = 291–299 | date = January 2018 | pmid = 29119218 | pmc = 5748395 | doi = 10.1007/s00213-017-4768-5 }}</ref>

Furthermore, nocturnal reactivation seems to share the same neural oscillatory patterns as reactivation during wakefulness, processes which might be coordinated by [[Theta wave|theta activity]].<ref name=":4">{{cite journal | vauthors = Schreiner T, Doeller CF, Jensen O, Rasch B, Staudigl T | title = Theta Phase-Coordinated Memory Reactivation Reoccurs in a Slow-Oscillatory Rhythm during NREM Sleep | journal = Cell Reports | volume = 25 | issue = 2 | pages = 296–301 | date = October 2018 | pmid = 30304670 | pmc = 6198287 | doi = 10.1016/j.celrep.2018.09.037 }}</ref> During wakefulness, theta oscillations have been often related to successful performance in memory tasks, and cued memory reactivations during sleep have been showing that theta activity is significantly stronger in subsequent recognition of cued stimuli as compared to uncued ones, possibly indicating a strengthening of memory traces and lexical integration by cuing during sleep.<ref>{{cite journal | vauthors = Schreiner T, Göldi M, Rasch B | title = Cueing vocabulary during sleep increases theta activity during later recognition testing | journal = Psychophysiology | volume = 52 | issue = 11 | pages = 1538–43 | date = November 2015 | pmid = 26235609 | doi = 10.1111/psyp.12505 }}</ref> However, the beneficial effect of TMR for memory consolidation seems to occur only if the cued memories can be related to prior knowledge.<ref>{{cite journal | vauthors = Groch S, Schreiner T, Rasch B, Huber R, Wilhelm I | title = Prior knowledge is essential for the beneficial effect of targeted memory reactivation during sleep | journal = Scientific Reports | volume = 7 | pages = 39763 | date = January 2017 | pmid = 28051138 | pmc = 5209656 | doi = 10.1038/srep39763 | bibcode = 2017NatSR...739763G | doi-access = free }}</ref>