Editing Chronobiology

{{Short description|Study of rhythms in biological processes of living organisms}}
{{distinguish|text=[[Biochronology]], paleontological chronology of biologic events based on fossil correlation}}
{{split|Biological rhythm|date=September 2020|discuss=Talk:Chronobiology#Proposed split}}

[[File:Biological clock human.PNG|upright=1.8|thumb|Overview, including some [[Physiology|physiological]] parameters, of the human [[Circadian rhythm|circadian rhythm ("biological clock")]].]]

'''Chronobiology''' is a field of [[biology]] that examines [[Time|timing processes]], including periodic (cyclic) phenomena in living organisms, such as their adaptation to [[sun|solar]]- and [[moon|lunar]]-related rhythms.<ref name="chrono">{{cite book |author=Patricia J. DeCoursey |author2=Jay C. Dunlap |author3=Jennifer J. Loros  |title=Chronobiology |publisher=Sinauer Associates Inc. |year=2003 |isbn=978-0-87893-149-1}}</ref> These cycles are known as biological rhythms. Chronobiology comes from the ancient Greek [[wikt:χρόνος|χρόνος]] (''chrónos'', meaning "time"), and [[biology]], which pertains to the study, or science, of [[life]]. The related terms ''chronomics'' and ''chronome'' have been used in some cases to describe either the [[molecular]] mechanisms involved in chronobiological phenomena or the more quantitative aspects of chronobiology, particularly where comparison of cycles between organisms is required.

Chronobiological studies include but are not limited to comparative [[anatomy]], [[physiology]], [[genetics]], [[molecular biology]] and [[behavior]] of organisms related to their [[biological rhythm]]s.<ref name="chrono"/>  Other aspects include [[epigenetics]], development, reproduction, ecology and evolution.

==The subject==
Chronobiology studies variations of the timing and duration of biological activity in living organisms which occur for many essential biological processes. These occur (a) in animals (eating, sleeping, mating, hibernating, migration, cellular regeneration, etc.), (b) in plants (leaf movements, [[photosynthetic]] reactions, etc.), and in microbial organisms such as fungi and protozoa. They have even been found in [[bacteria]], especially among the [[cyanobacteria]] (aka blue-green algae, see [[bacterial circadian rhythms]]). The best studied rhythm in chronobiology is the [[circadian rhythm]], a roughly 24-hour cycle shown by physiological processes in all these organisms. The term ''circadian'' comes from the [[Latin]] ''circa'', meaning "around" and ''dies'', "day", meaning "approximately a day." It is regulated by [[circadian clock]]s.

The circadian rhythm regulates behaviour including timing of the activity phase. Depending on their innate active phase, organisms can be classified into one of three categories:<ref>Nelson RJ. 2005. An Introduction to Behavioral Endocrinology. Sinauer Associates, Inc.: Massachusetts. Pg587.</ref>
* [[Diurnality|Diurnal]], which describes organisms active during daytime
* [[Nocturnal]], which describes organisms active in the night
* [[Crepuscular]], which describes animals primarily active during the dawn and dusk hours (ex: domestic cats,<ref>{{Cite journal |last=Merčnik |first=Neva |last2=Prevolnik Povše |first2=Maja |last3=Škorjanc |first3=Dejan |last4=Skok |first4=Janko |date=2023-12-01 |title=Chronobiology of free-ranging domestic cats: Circadian, lunar and seasonal activity rhythms in a wildlife corridor |url=https://www.sciencedirect.com/science/article/pii/S0168159123002666 |journal=Applied Animal Behaviour Science |volume=269 |pages=106094 |doi=10.1016/j.applanim.2023.106094 |issn=0168-1591}}</ref> white-tailed deer, some bats)

While [[circadian rhythms]] are generated by [[endogenous]] processes, they can be regulated by both endogenous and exogenous signals. Other biological cycles may be regulated by exogenous signals. 

Many other important cycles are also studied, including:
* [[Infradian rhythm]]s, which are cycles longer than a day. Examples include [[Circannual Cycle|circannual]] or annual cycles that govern migration or reproduction cycles in many plants and animals, or the human [[menstrual cycle]].
* [[Ultradian rhythm]]s, which are cycles shorter than 24 hours, such as the 90-minute [[REM cycle]], the 4-hour [[nasal cycle]], or the 3-hour cycle of [[growth hormone]] production.{{Citation needed|date=November 2023}}
* [[Tide|Tidal rhythms]], commonly observed in marine life, which follow the roughly 12.4-hour transition from high to low tide and back.
* [[Lunar rhythms]], which follow the [[lunar month]] (29.5 days). They are relevant e.g. for marine life, as the level of the tides is modulated across the lunar cycle. 

Within each cycle, the time period during which the process is more active is called the ''[[wikt:acrophase|acrophase]]''.<ref>Refinetti, Roberto (2006). ''Circadian Physiology''. CRC Press/Taylor & Francis Group. {{ISBN|0-8493-2233-2}}.  [http://www.circadian.org/dictionary.html Lay summary]</ref>  When the process is less active, the cycle is in its ''[[wikt:bathyphase|bathyphase]]'' or ''trough'' phase.  The particular moment of highest activity is the ''peak'' or ''maximum''; the lowest point is the ''nadir''.

==History==
A circadian cycle was first observed in the 18th century in the movement of plant leaves by the French scientist [[Jean-Jacques d'Ortous de Mairan]].<ref>for a description of circadian rhythms in plants by de Mairan, Linnaeus, and Darwin see [http://www.hhmi.org/biointeractive/museum/exhibit00/02_1.html] {{Webarchive|url=https://web.archive.org/web/20051225212335/http://www.hhmi.org/biointeractive/museum/exhibit00/02_1.html|date=2005-12-25}}</ref><ref>{{Cite web |title=A chronology of chronobiology |url=https://www.physoc.org/magazine-articles/a-chronology-of-chronobiology/ |access-date=2024-05-18 |website=The Physiological Society |language=en-GB}}</ref> In 1751, Swedish [[botanist]] and [[naturalist]] [[Carl Linnaeus]] (Carl von Linné) designed a [[Linnaeus' flower clock|flower clock]] using certain species of [[flowering plant]]s. By arranging the selected species in a circular pattern, he designed a clock that indicated the time of day by the flowers that were open at each given hour. For example, among members of the [[daisy family]], he used the [[Crepis|hawk's beard]] plant which opened its flowers at 6:30 am and the [[hawkbit]] which did not open its flowers until 7 am.<ref name="linnean">{{Cite web |url=http://www.linnean.org/Resources/LinneanSociety/Documents/Library-and-Archives/4-Floral%20Clock.pdf |title=The Linnean Tercentenary - Some Aspects of Linnaeus' Life - 4. Linnaeus' Floral Clock* |last=Gardiner |first=Brian G.|website=The Linnean Society |access-date=2013-12-12 |archive-url=https://web.archive.org/web/20131212123532/http://www.linnean.org/Resources/LinneanSociety/Documents/Library-and-Archives/4-Floral%20Clock.pdf |archive-date=2013-12-12 |url-status=dead }}</ref>

The 1960 symposium at [[Cold Spring Harbor Laboratory]] laid the groundwork for the field of chronobiology.<ref name="Kreitzman2004">{{cite book |author=Leon Kreitzman |author2=Russell G. Foster |title=Rhythms of life: the biological clocks that control the daily lives of every living thing |publisher=Yale University Press |location=New Haven, Conn |year=2004 |isbn=0-300-10969-5}}</ref>

It was also in 1960 that [[Patricia DeCoursey]] invented the [[phase response curve]], one of the major tools used in the field since.

[[Franz Halberg]] of the [[University of Minnesota]], who coined the word ''circadian'', is widely considered the "father of American chronobiology." However, it was [[Colin Pittendrigh]] and not Halberg who was elected to lead the ''Society for Research in Biological Rhythms'' in the 1970s. Halberg wanted more emphasis on the human and medical issues while Pittendrigh had his background more in evolution and ecology. With Pittendrigh as leader, the Society members did basic research on all types of organisms, plants as well as animals. More recently it has been difficult to get funding for such research on any other organisms than mice, rats, humans<ref>{{cite web |url=http://scienceblogs.com/clock/2006/07/clocktutorial_3_fortyfive_year.php |title=ClockTutorial #2a, Forty-Five Years of Pittendrigh's Empirical Generalizations |access-date=2007-12-23 |last=Zivkovic |first=Bora |date=2006-07-03 |work=A Blog Around the Clock |publisher=ScienceBlogs}}</ref><ref>{{cite web |url=http://scienceblogs.com/clock/2006/09/clocks_in_bacteria_v_how_about.php |title=Clocks in Bacteria V |access-date=2007-12-23 |last=Zivkovic |first=Bora |date=2006-05-17 |work=A Blog Around the Clock |publisher=ScienceBlogs}}</ref> and [[Drosophila melanogaster|fruit flies]].

==The role of Retinal Ganglion cells==
===Melanopsin as a circadian photopigment===
In 2002, [[Samer Hattar|Hattar]] and his colleagues showed that [[melanopsin]] plays a key role in a variety of photic responses, including [[pupillary light reflex]], and synchronization of the [[Circadian rhythm|biological clock]] to daily light-dark cycles. He also described the role of melanopsin in [[intrinsically photosensitive retinal ganglion cell|ipRGCs]]. Using a rat melanopsin gene, a melanopsin-specific antibody, and [[Immunocytochemistry|fluorescent immunocytochemistry]], the team concluded that melanopsin is expressed in some RGCs. Using a [[Beta-galactosidase]] assay, they found that these RGC [[axons]] exit the eyes together with the [[optic nerve]] and project to the [[suprachiasmatic nucleus]] (SCN), the primary circadian pacemaker in [[mammal]]s. They also demonstrated that the RGCs containing melanopsin were intrinsically photosensitive. Hattar concluded that melanopsin is the photopigment in a small subset of RGCs that contributes to the intrinsic photosensitivity of these cells and is involved in their non-image forming functions, such as photic entrainment and pupillary light reflex.<ref name="Fly in mammalian eye" />

===Melanopsin cells relay inputs from rods and cones===
[[File:Phototransduction and ipRGCs in mammals.jpg|thumb|alt=Phototransduction and ipRGCs in mammals|Light enters the eye and hits the retinal pigmented epithelium (maroon). This excites rods (grey) and cones (blue/red). These cells synapse onto bipolar cells (pink), which stimulate ipRGCs (green) and RGCs (orange). Both RGCs and ipRGCs transmit information to the brain through the optic nerve. Furthermore, light can directly stimulate the ipRGCs through its melanopsin photopigment. The ipRGCs uniquely project to the superchiasmatic nucleus, allowing the organism to entrain to light-dark cycles.]]
Hattar, armed with the knowledge that melanopsin was the photopigment responsible for the photosensitivity of ipRGCs, set out to study the exact role of the ipRGC in [[Photoentrainment (chronobiology)|photoentrainment]]. In 2008, Hattar and his research team transplanted [[diphtheria]] toxin [[genes]] into the [[mouse]] melanopsin gene locus to create [[mutation|mutant]] mice that lacked ipRGCs. The research team found that while the mutants had little difficulty identifying visual targets, they could not entrain to light-dark cycles.  These results led Hattar and his team to conclude that ipRGCs do not affect image-forming vision, but significantly affect non-image forming functions such as photoentrainment.<ref name="Fly in mammalian eye">{{cite web|last1=Graham|first1=Dustin|title=Melanopsin Ganglion Cells: A Bit of Fly in the Mammalian Eye|url=http://webvision.med.utah.edu/book/part-ii-anatomy-and-physiology-of-the-retina/elanopsin-ganglion-cells-a-bit-of-fly-in-the-mammalian-eye/|website=Webvision The Organization of the Retina and Visual System|publisher=University of Utah School of Medicine|accessdate=9 April 2015|url-status=dead|archiveurl=https://web.archive.org/web/20110427132440/http://webvision.med.utah.edu/book/part-ii-anatomy-and-physiology-of-the-retina/elanopsin-ganglion-cells-a-bit-of-fly-in-the-mammalian-eye/|archivedate=27 April 2011}}</ref>

===Distinct ipRGCs===
Further research has shown that ipRGCs project to different brain nuclei to control both non-image forming and image forming functions.<ref name=":0">{{Cite journal|title = Blurring the boundaries of vision: novel functions of intrinsically photosensitive retinal ganglion cells|last = Matynia|first = Anna|date = September 3, 2013|journal = Journal of Experimental Neuroscience|doi = 10.4137/JEN.S11267|pmc = 4089729|pmid=25157207|volume=7|pages=43–50}}</ref> These brain regions include the SCN, where input from ipRGCs is necessary to photoentrain circadian rhythms, and the [[pretectal area|olivary pretectal nucleus]] (OPN), where input from ipRGCs control the pupillary light reflex.<ref name=":1">{{Cite journal|title = Retinal Ganglion Cell Maps in the Brain: Implications for Visual Processing|last1 = Dhande|first1 = OS|date = November 19, 2013|journal = Current Opinion in Neurobiology|doi = 10.1016/j.conb.2013.08.006|pmc = 4086677|last2 = Huberman|first2 = AD|volume=24|issue = 1|pages=133–142|pmid=24492089}}</ref> Hattar and colleagues conducted research that demonstrated that ipRGCs project to hypothalamic, thalamic, stratal, brainstem and limbic structures.<ref>{{Cite journal|title = Neuroimaging, Cognition, Light and Circadian Rhythms|author1=Gaggioni G |author2=Maquet P |author3=Schmidt C |author4=Dijk Dj |author5=Vandealle G |date = July 8, 2014|journal = Frontiers in Systems Neuroscience|doi = 10.3389/fnsys.2014.00126|pmc = 4086398|pmid=25071478|volume=8|pages=126|doi-access=free }}</ref> Although ipRGCs were initially viewed as a uniform population, further research revealed that there are several subtypes with distinct morphology and physiology.<ref name=":0" /> Since 2011, Hattar's laboratory<ref>{{cite web|title=The Hattar Lab|url=http://hattarlab.johnshopkins.edu/pages/research.php|publisher=Johns Hopkins University|accessdate=27 December 2016|date=2014}}</ref> has contributed to these findings and has successfully distinguished subtypes of ipRGCs.<ref name=":1"/>

===Diversity of ipRGCs===
Hattar and colleges utilized [[Cre-Lox recombination|Cre-based]] strategies for labeling ipRGCs to reveal that there are at least five ipRGC subtypes that project to a number of central targets.<ref name=":1"/> Five classes of ipRGCs, M1 through M5, have been characterized to date in rodents. These classes differ in morphology, dendritic localization, melanopsin content, electrophysiological profiles, and projections.<ref name=":0"/>

===Diversity in M1 cells===
Hattar and his co-workers discovered that, even among the subtypes of ipRGC, there can be designated sets that differentially control circadian versus pupillary behavior. In experiments with M1 ipRGCs, they discovered that the transcription factor [[POU4F2|Brn3b]] is expressed by M1 ipRGCs that target the OPN, but not by ones that target the SCN. Using this knowledge, they designed an experiment to cross Melanopsin-[[Cre-Lox recombination|Cre]] mice with mice that conditionally expressed a toxin from the Brn3b locus. This allowed them to selectively ablate only the OPN projecting M1 ipRGCS, resulting in a loss of pupil reflexes. However, this did not impair circadian photo entrainment. This demonstrated that the M1 ipRGC consist of molecularly distinct subpopulations that innervate different brain regions and execute specific light-induced functions.<ref name=":1"/> This isolation of a 'labeled line' consisting of differing molecular and functional properties in a highly specific ipRGC subtype was an important first for the field. It also underscored the extent to which molecular signatures can be used to distinguish between RGC populations that would otherwise appear the same, which in turn facilitates further investigation into their specific contributions to visual processing.<ref name=":1"/>

==Psychological impact of light exposure==
Previous studies in circadian biology have established that exposure to light during abnormal hours leads to [[sleep deprivation]] and disruption of the circadian system, which affect mood and [[Cognition|cognitive functioning]]. While this indirect relationship had been corroborated, not much work had been done to examine whether there was a direct relationship between irregular light exposure, aberrant mood, cognitive function, normal sleep patterns and circadian oscillations. In a study published in 2012, the Hattar Laboratory was able to show that deviant light cycles directly induce [[Depression (mood)|depression]]-like symptoms and lead to impaired learning in mice, independent of [[sleep]] and circadian oscillations.<ref name=Dulcis>{{cite journal|last1=Dulcis|first1=Davide|last2=Jamshidi|first2=Pouya|last3=Leutgeb|first3=Stefan|last4=Spitzer|first4=Nicholas C.|title=Neurotransmitter Switching in the Adult Brain Regulates Behavior|journal=Science|date=26 April 2013|volume=340|issue=6131|pages=449–453|bibcode=2013Sci...340..449D|doi=10.1126/science.1234152|pmid=23620046|s2cid=44911091}}</ref>

===Effect on mood===
ipRGCs project to areas of the brain that are important for regulating circadian rhythmicity and sleep, most notably the [[Suprachiasmatic nucleus|SCN]], subparaventricular nucleus, and the ventrolateral preoptic area. In addition, ipRGCs transmit information to many areas in the [[limbic system]], which is strongly tied to emotion and memory. To examine the relationship between deviant light exposure and behavior, Hattar and his colleagues studied mice exposed to alternating 3.5-hour light and dark periods (T7 mice) and compared them with mice exposed to alternating 12-hour light and dark periods (T24 mice).  Compared to a T24 cycle, the T7 mice got the same amount of total sleep and their circadian expression of [[PER2]], an element of the SCN pacemaker, was not disrupted. Through the T7 cycle, the mice were exposed to light at all circadian phases. Light pulses presented at night lead to expression of the transcription factor [[c-Fos]] in the [[amygdala]], [[habenula|lateral habenula]], and subparaventricular nucleus further implicating light's possible influence on mood and other cognitive functions.<ref name=Masana>{{cite journal|last1=Masana|first1=MI|title=Light-induced c-fos mRNA expression in the suprachiasmatic nucleus and the retina of C3H/HeN mice.|journal=Molecular Brain Research|date= December 1996|volume=42|issue=2|pages=193–201|doi=10.1016/s0169-328x(96)00031-9|pmid=9013774}}</ref>

Mice subjected to the T7 cycle exhibited depression-like symptoms, exhibiting decreased preference for [[sucrose]] (sucrose anhedonia) and exhibiting more immobility than their T24 counterparts in the [[behavioural despair test|forced swim test (FST)]].  Additionally, T7 mice maintained rhythmicity in serum [[corticosterone]], however the levels were elevated compared to the T24 mice, a trend that is associated with depression. Chronic administration of the antidepressant [[Fluoxetine]] lowered corticosterone levels in T7 mice and reduced depression-like behavior while leaving their circadian rhythms unaffected.<ref name=Dulcis />

===Effect on learning===
The [[hippocampus]] is a structure in the limbic system that receives projections from ipRGCs. It is required for the consolidation of [[short-term memory|short-term memories]] into [[long-term memory|long-term memories]] as well as spatial orientation and navigation. Depression and heightened serum corticosterone levels are linked to impaired hippocampal learning. Hattar and his team analyzed the T7 mice in the [[Morris water navigation task|Morris water maze (MWM)]], a spatial learning task that places a mouse in a small pool of water and tests the mouse's ability to locate and remember the location of a rescue platform located just below the waterline.  Compared to the T24 mice, the T7 mice took longer to find the platform in subsequent trials and did not exhibit a preference for the quadrant containing the platform. In addition, T7 mice exhibited impaired hippocampal [[long-term potentiation]] (LTP) when subjected to [[Theta Burst Stimulation|theta burst stimulation]] (TBS). Recognition memory was also affected, with T7 mice failing to show preference for novel objects in the novel object recognition test.<ref name=Sauer>{{cite journal|last1=Sauer|first1=Jonas-Frederic|title=Impaired fast-spiking interneuron function in a genetic mouse model of depression|journal=eLife|date=3 March 2015|volume=4|doi=10.7554/elife.04979|pmid=25735038|pmc=4374525 |doi-access=free }}</ref>

===Necessity of ipRGCs===
Mice without (Opn4<sup>aDTA/aDTA</sup> mice) are not susceptible to the negative effects of an aberrant light cycle, indicating that light information transmitted through these cells plays an important role in regulation of mood and cognitive functions such as learning and memory.<ref name=Monteggia>{{cite journal|last1=Monteggia|first1=Lisa|author-link1=Lisa Monteggia|last2=Kavalali|first2=E. T.|title=Circadian rhythms: Depression brought to light|journal=Nature|volume=491|issue=7425|pages=537–538|doi=10.1038/nature11752|pmid=23151474|year=2012|bibcode=2012Natur.491..537M|s2cid=4391543}}</ref>

==Research developments==
;Light and melatonin
More recently, [[light therapy]] and [[melatonin (medication)|melatonin]] administration have been explored by [[Alfred J. Lewy]] ([[OHSU]]), [[Josephine Arendt]] ([[University of Surrey]], UK) and other researchers as a means to reset animal and human circadian rhythms. Additionally, the presence of low-level light at night accelerates circadian re-entrainment of hamsters of all ages by 50%; this is thought to be related to simulation of moonlight.<ref>{{Cite journal | last1 = Frank | first1 = D. W. | last2 = Evans | first2 = J. A. | last3 = Gorman | first3 = M. R. | doi = 10.1177/0748730409360890 | title = Time-Dependent Effects of Dim Light at Night on Re-Entrainment and Masking of Hamster Activity Rhythms | journal = Journal of Biological Rhythms | volume = 25 | issue = 2 | pages = 103–112 | year = 2010 | pmid =  20348461| s2cid = 41985077 | doi-access = free }}</ref>

In the second half of 20th century, substantial contributions and formalizations have been made by Europeans such as [[Jürgen Aschoff]] and [[Colin Pittendrigh]], who pursued different but complementary views on the phenomenon of [[entrainment (chronobiology)|entrainment]] of the circadian system by light (parametric, continuous, tonic, gradual vs. nonparametric, discrete, phasic, instantaneous, respectively<ref>see [http://jbr.sagepub.com/cgi/reprint/15/3/195 this historical article], subscription required</ref>).

;Chronotypes
Humans can have a propensity to be morning people or evening people; these behavioral preferences are called [[chronotype]]s for which there are various assessment questionnaires and biological marker correlations.<ref>{{Cite book|title=The Power of When|last=Breus, PHD|first=Michael|publisher=Little Brown and Company|year=2016|isbn=978-0-316-39126-9}}</ref>

;Mealtimes
There is also a food-entrainable biological clock, which is not confined to the suprachiasmatic nucleus. The location of this clock has been disputed. Working with mice, however, Fuller ''et al.'' concluded that the food-entrainable clock seems to be located in the dorsomedial [[hypothalamus]]. During restricted feeding, it takes over control of such functions as activity timing, increasing the chances of the animal successfully locating food resources.<ref>{{cite journal |last=Fuller |first=Patrick M. |author2=Jun Lu |author3=Clifford B. Saper  |date=2008-05-23 |title=Differential Rescue of Light- and Food-Entrainable Circadian Rhythms |journal=Science |volume=320 |issue=5879 |pages=1074–1077 |pmid=18497298 |doi=10.1126/science.1153277 |bibcode = 2008Sci...320.1074F |pmc=3489954}}</ref>

;Diurnal patterns on the Internet
In 2018 a study published in PLoS ONE showed how 73 psychometric indicators measured on Twitter Content follow a diurnal pattern.
<ref>{{cite journal |last=Dzogang |first=Fabon |author2=Stafford Lightman |author3= Nello Cristianini  |date=2018-06-20 |title= Diurnal Variation of Psychometric Indicators in Twitter Content |journal= PLOS ONE |volume=13 |issue=6 |pages=e0197002 |doi= 10.1371/journal.pone.0197002 |pmid=29924814 |pmc=6010242 |bibcode=2018PLoSO..1397002D |doi-access=free }}</ref> 
A followup study appeared on Chronobiology International in 2021 showed that these patterns were not disrupted by the 2020 UK lockdown.<ref>{{cite journal |last=Wang |first=Sheng |author2=Stafford Lightman |author3= Nello Cristianini  |date=2021-06-17 |title= Effect of the lockdown on diurnal patterns of emotion expression in Twitter |journal= Chronobiology International |volume=38 |issue=11 |pages=1591–1610 |doi= 10.1080/07420528.2021.1937198|pmid=34134583 |s2cid=235462661 |url=https://research-information.bris.ac.uk/en/publications/d064a56f-5da0-4210-95dc-f575acdf3b68 |hdl=1983/d064a56f-5da0-4210-95dc-f575acdf3b68 |hdl-access=free }}</ref>

;Modulators of circadian rhythms
In 2021, scientists reported the development of a light-responsive days-lasting modulator of circadian rhythms of tissues [[Casein kinase 1#Circadian rhythm|via Ck1 inhibition]]. Such modulators may be useful for chronobiology research and repair of organs that are "out of sync".<ref>{{cite news |title=Resetting the biological clock by flipping a switch |url=https://phys.org/news/2021-05-resetting-biological-clock-flipping.html |access-date=14 June 2021 |work=phys.org |language=en}}</ref><ref>{{cite journal |last1=Kolarski |first1=Dušan |last2=Miró-Vinyals |first2=Carla |last3=Sugiyama |first3=Akiko |last4=Srivastava |first4=Ashutosh |last5=Ono |first5=Daisuke |last6=Nagai |first6=Yoshiko |last7=Iida |first7=Mui |last8=Itami |first8=Kenichiro |last9=Tama |first9=Florence |last10=Szymanski |first10=Wiktor |last11=Hirota |first11=Tsuyoshi |last12=Feringa |first12=Ben L. |title=Reversible modulation of circadian time with chronophotopharmacology |journal=Nature Communications |date=2021-05-26 |volume=12 |issue=1 |pages=3164 |doi=10.1038/s41467-021-23301-x |pmid=34039965 |pmc=8155176 |bibcode=2021NatCo..12.3164K |language=en |issn=2041-1723}} [[File:CC-BY icon.svg|50px]] Available under [https://creativecommons.org/licenses/by/4.0/ CC BY 4.0].</ref>

==Other fields==
Chronobiology is an interdisciplinary field of investigation. It interacts with medical and other research fields such as [[sleep medicine]], [[endocrinology]], [[geriatrics]], [[sports medicine]], [[space medicine]], [[psychiatry]] and [[photoperiodism]].<ref>{{cite book |last=Postolache |first=Teodor T. |title=Sports Chronobiology, An Issue of Clinics in Sports Medicine |publisher=Saunders |year=2005 |isbn=978-1-4160-2769-0}}</ref><ref>{{cite book |last=Ernest Lawrence Rossi |first=David Lloyd |title=Ultradian Rhythms in Life Processes: Inquiry into Fundamental Principles of Chronobiology and Psychobiology |publisher=Springer-Verlag Berlin and Heidelberg GmbH & Co. K |year=1992 |isbn=978-3-540-19746-1}}</ref><ref>{{cite book |last=Hayes |first=D.K. |title=Chronobiology: Its Role in Clinical Medicine, General Biology, and Agriculture |publisher=John Wiley & Sons |year=1990 |isbn=978-0-471-56802-5}}</ref>

==See also==
* [[Bacterial circadian rhythms]]
* [[Biological clock (aging)]]
* [[Circadian rhythm]]
* [[Circannual cycle]]
* [[Circaseptan]], 7-day biological cycle
* [[Familial sleep traits]]
* [[Frank A. Brown, Jr.]]
* [[Hitoshi Okamura]]
* [[Light effects on circadian rhythm]]
* [[Photoperiodism]]
* [[Suprachiasmatic nucleus]]
* [[Scotobiology]]
* [[Time perception]]
* [[Malcolm von Schantz]]

==References==
{{Reflist}}

==Further reading==
{{Refbegin|colwidth=40em}}
* Hastings, Michael, "''[http://bmj.bmjjournals.com/cgi/content/full/317/7174/1704 The brain, circadian rhythms, and clock genes]''". Clinical review" ''BMJ'' 1998;317:1704-1707 19 December.
* U.S. Congress, Office of Technology Assessment, "''[http://www.princeton.edu/~ota/disk1/1991/9108/9108.PDF Biological Rhythms: Implications for the Worker]''". U.S. Government Printing Office, September 1991. Washington, DC. OTA-BA-463. NTIS PB92-117589
* Ashikari, M., Higuchi, S., Ishikawa, F., and Tsunetsugu, Y., "''[http://www.cam.ac.uk/societies/cujif/abstract/020825.htm Interdisciplinary Symposium on 'Human Beings and Environments': Approaches from Biological Anthropology, Social Anthropology and Developmental Psychology]''". Sunday, 25 August 2002
*"''Biorhythm experiment management plan''", NASA, Ames Research Center. Moffett Field, 1983.
* "''Biological Rhythms and Human Adaptation to the Environment''". US Army Medical Research and Materiel Command (AMRMC), US Army Research Institute of Environmental Medicine.
* Ebert, D., K.P. Ebmeier, T. Rechlin, and W.P. Kaschka, "''Biological Rhythms and Behavior''", ''Advances in Biological Psychiatry''. ISSN 0378-7354
* Horne, J.A. (Jim) & Östberg, Olov (1976). A Self-Assessment Questionnaire to determine Morningness-Eveningness in Human Circadian Rhythms. International Journal of Chronobiology, 4, 97–110.
* Roenneberg, Till, Cologne (2010). Wie wir ticken – Die Bedeutung der Chronobiologie für unser Leben, Dumont, {{ISBN|978-3-8321-9520-5}}.
* [http://www.linnean.org/ The Linnean Society of London]
{{Refend}}

==External links==
{{Commons category}}
{{Refbegin|}}
*[http://halbergchronobiologycenter.umn.edu Halberg Chronobiology Center] at the [[University of Minnesota]], founded by [[Franz Halberg]], the "Father of Chronobiology"
*The [[University of Virginia]] offers an [https://web.archive.org/web/20030602130556/http://www.cbt.virginia.edu/tutorial/TUTORIALMAIN.html online tutorial] on chronobiology.
*See the [[Science Museum of Virginia]] publication [https://web.archive.org/web/20051228024848/http://www.smv.org/jil/mll/ktwo/MLLK-2TL-CA-canpla.pdf Can plants tell time?]
*The [http://www.manchester.ac.uk/ University of Manchester] has an informative [https://web.archive.org/web/20071207231902/http://cal.man.ac.uk/student_projects/1999/sanders/home.htm Biological Clock Web Site]
*[https://web.archive.org/web/20080127013416/http://www.psych.uni-goettingen.de/home/ertel/ertel-dir/myresearch/1retrospect/ S Ertel's analysis of Chizhevsky's work]
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[[Category:Chronobiology| ]]
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