Fatigue

==== Mental ====  <!--Linked from [[Template:Mental processes]]-->

Mental fatigue is a temporary inability to maintain optimal cognitive performance. The onset of mental fatigue during any cognitive activity is gradual, and depends upon an individual's cognitive ability, and also upon other factors, such as sleep deprivation and overall health.

Mental fatigue has also been shown to decrease physical performance.<ref name="Marcora 2009 857–864" /> It can manifest as [[somnolence]], [[lethargy]], [[directed attention fatigue]], or disengagement. Research also suggests that mental fatigue is closely linked to the concept of [[ego depletion]], though the validity of the concept is disputed. For example, one pre-registered study of 686 participants found that after exerting mental effort, people are likely to disengage and become less interested in exerting further effort.<ref>{{cite journal | vauthors = Lin H, Saunders B, Friese M, Evans NJ, Inzlicht M | title = Strong Effort Manipulations Reduce Response Caution: A Preregistered Reinvention of the Ego-Depletion Paradigm | journal = Psychological Science | volume = 31 | issue = 5 | pages = 531–547 | date = May 2020 | pmid = 32315259 | pmc = 7238509 | doi = 10.1177/0956797620904990 }}</ref>

Decreased attention can also be described as a more or less decreased [[level of consciousness]].<ref>{{cite book|title=Difficult Diagnosis 2| vauthors  = Giannini AJ |publisher=W.B. Saunders Co.|year=1991|isbn=978-0-7216-3481-4| veditors = Taylor RB |location= Philadelphia|page=156|chapter=Fatigue, Chronic|oclc=954530793}}</ref> In any case, this can be dangerous when performing tasks that require constant concentration, such as operating large vehicles. For instance, a person who is sufficiently somnolent may experience [[microsleep]]. However, objective cognitive testing can be used to differentiate the neurocognitive deficits of brain disease from those attributable to tiredness.<ref name="pmid29355911">{{cite journal |vauthors=Possin KL, Moskowitz T, Erlhoff SJ, Rogers KM, Johnson ET, Steele NZ, Higgins JJ, Stiver J, Alioto AG, Farias ST, Miller BL, Rankin KP |title=The Brain Health Assessment for Detecting and Diagnosing Neurocognitive Disorders |journal=J Am Geriatr Soc |volume=66 |issue=1 |pages=150–156 |date=January 2018 |pmid=29355911 |pmc=5889617 |doi=10.1111/jgs.15208 |url=}}</ref><ref name="pmid30884965">{{cite journal |vauthors=Menzies V, Kelly DL, Yang GS, Starkweather A, Lyon DE |title=A systematic review of the association between fatigue and cognition in chronic noncommunicable diseases |journal=Chronic Illn |volume=17 |issue=2 |pages=129–150 |date=June 2021 |pmid=30884965 |pmc=6832772 |doi=10.1177/1742395319836472 |url=}}</ref><ref name="pmid38079429">{{cite journal |vauthors=Elliott TR, Hsiao YY, Randolph K, Urban RJ, Sheffield-Moore M, Pyles RB, Masel BE, Wexler T, Wright TJ |title=Efficient assessment of brain fog and fatigue: Development of the Fatigue and Altered Cognition Scale (FACs) |journal=PLOS ONE |volume=18 |issue=12 |pages=e0295593 |date=2023 |pmid=38079429 |pmc=10712873 |doi=10.1371/journal.pone.0295593 |doi-access=free |bibcode=2023PLoSO..1895593E |url=}}</ref><!--It would also be interesting to read more about the ways in which the [[neurocognitive]] deficits of caused by fatigue differ from those caused by tiredness-->

The [[perception]] of mental fatigue is believed to be modulated by the brain's [[reticular activating system]] (RAS).<ref name="pmid24926625">{{cite journal |vauthors=Ishii A, Tanaka M, Watanabe Y |title=Neural mechanisms of mental fatigue |journal=Rev Neurosci |volume=25 |issue=4 |pages=469–79 |date=2014 |pmid=24926625 |doi=10.1515/revneuro-2014-0028 |url=}}</ref><ref name="pmid28690375">{{cite journal |vauthors=Garcia-Rill E, Virmani T, Hyde JR, D'Onofrio S, Mahaffey S |title=Arousal and the control of perception and movement |journal=Curr Trends Neurol |volume=10 |issue= |pages=53–64 |date=2016 |pmid=28690375 |pmc=5501251 |doi= |url=}}</ref><ref name="pmid31216564">{{cite journal |vauthors=Jones BE |title=Arousal and sleep circuits |journal=Neuropsychopharmacology |volume=45 |issue=1 |pages=6–20 |date=January 2020 |pmid=31216564 |pmc=6879642 |doi=10.1038/s41386-019-0444-2 |url=}}</ref><ref name="pmid37155119">{{cite journal |vauthors=Taran S, Gros P, Gofton T, Boyd G, Briard JN, Chassé M, Singh JM |title=The reticular activating system: a narrative review of discovery, evolving understanding, and relevance to current formulations of brain death |journal=Can J Anaesth |volume=70 |issue=4 |pages=788–795 |date=April 2023 |pmid=37155119 |pmc=10203024 |doi=10.1007/s12630-023-02421-6 |url=}}</ref><ref name="pmid31751025">{{cite book|pmid=31751025|title=Neuroanatomy, Reticular Activating System|date=2024 | vauthors = Arguinchona JH, Tadi P }}</ref>

Fatigue impacts a driver's reaction time, awareness of hazards around them and their attention. Drowsy drivers are three times more likely to be involved in a car crash, and being awake over 20 hours is the equivalent of driving with a blood-alcohol concentration level of 0.08%.<ref>{{cite web |title=Drowsy Driving is Impaired Driving |url=https://www.nsc.org/road-safety/safety-topics/fatigued-driving |website=National Safety Council |access-date=31 January 2019 |archive-date=1 February 2019 |archive-url=https://web.archive.org/web/20190201014026/https://www.nsc.org/road-safety/safety-topics/fatigued-driving |url-status=live }}</ref>