Untermensch

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Untermensch 

Cover of the Nazi propaganda brochure "Der Untermensch" ("The Subhuman"), 1942. The SS booklet depicted the natives of the Soviet Union as "subhumans".

Untermensch (German pronunciation: [ˈʔʊntɐˌmɛnʃ] ^ⓘ; plural: Untermenschen) is a German-language word literally meaning 'underhuman or 'subhuman', which was extensively used by Germany's Nazi Party to refer to their opponents and non-Aryan people they deemed as inferior. It was mainly used against "the masses from the East", that is Jews, Roma, and Slavs (mainly ethnic Poles, Belarusians, Ukrainians, Russians and Serbs).

The term was also applied to "Mischling" (persons of mixed "Aryan" and non-Aryan ancestry) and black people. The physically and mentally disabled, homosexuals, transgender, political dissidents and—on rare instances—POWs from Western Allied armies, were also considered Untermenschen and were to be exterminated in the Holocaust. According to the Generalplan Ost, the Slavic population of East-Central Europe was to be reduced in part through mass murder in the Holocaust for Lebensraum, with a significant number expelled farther east to Siberia and used as forced labour in the Reich. These concepts were an important part of the Nazi racial policy.

Etymology

The term "under man" was introduced by the American author and Ku Klux Klan member Lothrop Stoddard in his 1922 book The Revolt Against Civilization: The Menace of the Under-man. Stoddard applies the term to those whom he considers unable to flourish in civilization due to their inferior heredity ("The word inferior has, however, been so often employed as a synonym for degenerate that it tends to produce confusion of thought, and to avoid this I have coined a term which seems to describe collectively all those kinds of persons whom I have just discussed. This term is The Under-Man—the man who measures under the standards of capacity and adaptability imposed by the social order in which he lives". (p. 23)). Therefore, the term has no racial connotations. Indeed, in his book Stoddard maintains that without eugenics any and all civilizations—irrespective of race, time and geography—have been, are and inevitably will be prone to gradual degradation. The Nazi Party later used the term in propaganda, possibly influenced in part from the title of the book's German edition Der Kulturumsturz: Die Drohung des Untermenschen (1925).

Austro-Hungarian postcard made in 1914 which features the rhyming slogan "Serbia must die!" Such images were representative of the social attitudes underlying the concept of untermensch.

The German word Untermensch had been used in earlier periods, but it had not been used in a racial sense; for example, it was used in the 1899 novel Der Stechlin by Theodor Fontane. Since most writers who employed the term did not address the question of when and how the word entered the German language, in English, Untermensch is usually translated as "subhuman". The leading Nazi who attributed the concept of the East-European "under man" to Stoddard was Alfred Rosenberg who, referring to communists of the Soviet Russia, wrote in his Der Mythus des zwanzigsten Jahrhunderts (1930) that "this is the kind of human being that Lothrop Stoddard has called the 'under man.'" ["...den Lothrop Stoddard als 'Untermenschen' bezeichnete."] Despite Nazi official support for The Myth of the Twentieth Century and Rosenberg's prominent role in promoting Nazi ideology, Adolf Hitler declared that it was not to be considered the official ideology of the Nazi Party, and he privately described the book as "mysticism" and "nonsense". Albert Speer claimed that Goebbels mocked Alfred Rosenberg. Goebbels also called the book a "philosophical belch".

It is possible that Stoddard constructed his "under man" as an opposite of Friedrich Nietzsche's Übermensch (superman) concept. Stoddard does not explicitly say this, but he critically refers to the "superman" idea at the end of his book (p. 262). Wordplays with Nietzsche's term seem to have been used repeatedly as early as the 19th century and, due to the German linguistic trait of being able to combine prefixes and roots almost at will in order to create new words, this development can be considered logical. For instance, German author Theodor Fontane contrasts the Übermensch/Untermensch word pair in chapter 33 of his novel Der Stechlin. Nietzsche used the term Untermensch at least once in contrast to Übermensch in Die fröhliche Wissenschaft (1882). Earlier examples of Untermensch include Romanticist Jean Paul using the term in his novel Hesperus (1795) in reference to an Orangutan (Chapter "8. Hundposttag").

Nazi propaganda

In a speech which he delivered to the Bavarian regional parliament in 1927, the Nazi Party propagandist Julius Streicher, publisher of Der Stürmer, used the term Untermensch referring to the communists of the German Bavarian Soviet Republic:

It happened at the time of the [Bavarian] Soviet Republic: When the unleashed subhumans rambled murdering through the streets, the deputies hid behind a chimney in the Bavarian parliament.

A chart used to illustrate the Nazi Nuremberg Laws introduced in 1935

The Nazi party and thereafter also the regime (1933–1945) repeatedly used the term Untermensch in writings and speeches which they directed against the Jews. In the pamphlet "The SS as an Anti-Bolshevist Fighting Organization", published in 1936, Himmler wrote:

We shall take care that never again in Germany, the heart of Europe, will the Jewish-Bolshevik revolution of subhumans be able to be kindled either from within or through emissaries from without.

In his speech "Weltgefahr des Bolschewismus" ("World danger of Bolshevism") in 1936, Joseph Goebbels said that "subhumans exist in every people as a leavening agent". At the 1935 Nazi party congress rally at Nuremberg, Goebbels also declared that, “Bolshevism is the declaration of war by Jewish-led international subhumans against culture itself."

The most notorious example of the usage of the term Untermensch by the Nazis is a Schutzstaffel (SS) brochure entitled "Der Untermensch [de]", distributed by the Reich Security Main Office under the directives of Heinrich Himmler. Published in 1942 after the start of Operation Barbarossa, it is around 50 pages long and consists, for the most part, of photos portraying the natives of Eastern Europe in an extremely negative way. Nearly four million copies of the pamphlet were printed in the German language and distributed across German-occupied territories. The contents of the "Der Untermensch" brochure extensively emphasized Himmler's racist demonization of Russians as "bestial untermenschen" and Jews as "the decisive leader of untermenschen". It was translated into Greek, French, Dutch, Danish, Bulgarian, Hungarian, Czech and seven other languages. It gives the following definition of an Untermensch:

The subhuman is a biological creature, crafted by nature, which has hands, legs, eyes and mouth, even the semblance of a brain. Nevertheless, this terrible creature is only a partial human being. Although it has features similar to a human, the subhuman is lower on the spiritual and psychological scale than any animal. Inside this being is a cruel chaos of wild, unrestrained passions, nameless desire for destruction, the most primitive desires, the most naked meanness.

Spanish Falangism

In Spain, in addition to the term underman, the terms subhuman and degenerate are frequent in speeches and articles, especially from the 1930s. These are words used naturally in the newspapers, without explanations of the specific meaning, so it can be deduced that they were general knowledge. They are terms that increase in intensity during the October Events, and during the civil war.

As the civil war approaches or takes place, there is a divergence in the meaning of subhuman, on the rebel side it acquires a racial/eugenic meaning, beside ideologic, while on the republican side it is more of a cultural type.

Once the war was won by the rebel side, Francoism, similar to Nazi Germany (and Soviet Russia as well), promoted the idea of creating a new man, which led to the brutal repression of the Spanish population. Gonzalo de Aguilera, the press officer for the Nationalist faction during the Spanish Civil War, made the following classicidal statements to journalist John T. Whitaker:

"We have to kill, kill, you know? They are like animals, you know, and we cannot expect them to get rid of the virus of Bolshevism. After all, rats and lice are the carriers of the plague. Now I hope you understand what we mean by the regeneration of Spain... Our programme consists... of exterminating one third of the male population of Spain. That would cleanse the country and get rid of the proletariat. And it is also economically convenient. There will be no more unemployment in Spain, do you understand?"

Policies of Nazi Germany

When faced with increasing military manpower shortages, the Nazi regime used soldiers from some Slavic countries, firstly from the Reich's allies Croatia and Slovakia as well as within occupied territories. The concept of the Slavs in particular being Untermenschen served the Nazis' political goals; it was used to justify their expansionist policy and especially their aggression against Poland and the Soviet Union in order to achieve Lebensraum, particularly in Ukraine. Early plans of the Nazi officials (summarized as Generalplan Ost) envisioned the ethnic cleansing and extermination of no fewer than 50 million people, who were not considered fit for Germanization, from territories it wanted to conquer in Europe. Nazi planners considered Ukraine's chernozem ("black earth") soil as a particularly desirable zone for colonization.

Eastern Europe

Main article: Generalplan Ost

During the war, Nazi propaganda instructed Wehrmacht officers to tell their soldiers to target people whom they considered "Jewish Bolshevik subhumans". In addition, Nazi Germany conducted its warfare against the Soviet Union as a racial war targeting Jews, Romanis, Slavs, and various indigenous inhabitants of Eastern Europe who were categorized as "untermenschen" in the Nazi ideology. Nazis viewed Russians as animalistic sub-humans who were incapable of mounting any form of collective resistance against a German invasion. Nazi anti-Slavism was also tied to the Judeo-Bolshevik conspiracy theory; which claimed that Slavs were inferior people controlled by Jews as pawns in their plots against Aryans.

Prior to the launch of Operation Barbarossa, the Wehrmacht's High Command began issuing orders to enable German soldiers to indiscriminately target the inhabitants of Eastern Europe and unleash systematic violence against entire populations. German Army was instructed to grant carte blanche to the anti-Jewish massacres carried out by the Einsatzgruppen death squads in German-occupied territories. “Guidelines for the Conduct of the Troops in Russia” issued by the German High Command on 19 May 1941, ordered German troops to target Jews, partisans, Bolsheviks, etc. and described the war in Eastern Europe as a "historic task to liberate the German people once forever from the Asiatic-Jewish danger". In 1943 Himmler issued a secret order for the destruction of the Warsaw Ghetto in order to eliminate the "living space" of 500,000 Untermenschen, unsuitable for the Germans.

Sub-human types

The Nazis divided the people who they considered the sub-humans into different types; they placed priority on the extermination of the Jews, and Roma, and the exploitation of others as slaves.

Historian Robert Jan van Pelt writes that for the Nazis, "it was only a small step to a rhetoric pitting the European Mensch against the Soviet Untermensch, which had come to mean a Russian in the clutches of Judeo-Bolshevism."

The Untermensch concept included Jews, Roma and Sinti (Gypsies), and Slavic peoples such as Poles, Ukrainians, and Russians. Slavs were regarded as Untermenschen, barely fit for exploitation as slaves. Hitler and Goebbels compared them to the "rabbit family" or to "stolid animals" that were "idle" and "disorganized" and spread like a "wave of filth". However, some among the Slavs who happened to have Nordic racial features were deemed to have distant Germanic descent which meant partially "Aryan" origin, and if under 10 years old, they were to be Germanized (see: kidnapping of children by Nazi Germany).

A 1940 poster listing the obligations imposed on Polish workers in Germany under the Polish decrees, including the death penalty for sexual relations with a German.

The Nazis were utterly contemptuous of the Slavs, as even prior to World War II, Slavs – particularly the Poles – were deemed to be inferior to Germans and other Aryans. After Adolf Hitler gained political power in Germany, the concept of non-Aryan "sub-human slave-material" was developed and started to be used also towards other Slavic peoples. Poles were at the bottom of the Slavic "racial hierarchy" established by the Nazis. Soon after the Molotov–Ribbentrop Pact expired, Russians also started to be seen as "subhumans". Similarly, Belarusians, Czechs, Slovaks, and Ukrainians were considered to be inferior. Nonetheless, there were Slavs such as Bosniaks, Bulgarians, and Croats who collaborated with Nazi Germany that were still being perceived as not racially "pure" enough to reach the status of Germanic peoples, yet they were eventually considered ethnically better than other Slavs, mostly due to theories about these nations having a minimal amount of Slavic genes and considerable admixtures of Germanic and Turkic blood.

In order to forge a strategic alliance with the Independent State of Croatia—a puppet state created after the invasion of Yugoslavia and the Kingdom of Bulgaria, the Nazis deviated from a strict interpretation of their racial ideology, and Croats were officially described as "more Germanic than Slav", a notion supported by Croatia's fascist (Ustashe) dictator Ante Pavelić who maintained that the "Croats were descendants of the ancient Goths" and "had the Panslav idea forced upon them as something artificial". Hitler also deemed the Bulgarians to be "Turkoman" in origin.

This poster (from around 1938) reads: "60,000 Reichsmark is what this person suffering from a hereditary defect costs the People's community during his lifetime. Fellow citizen, that is your money too. Read the Neues Volk, the monthly magazine of the Office of Racial Policy of the NSDAP."

While the Nazis were inconsistent in the implementation of their policy – for instance, mostly implementing the Final Solution while also implementing Generalplan Ost – the democidal death toll was in the range of tens of millions of victims. It is related to the concept of "life unworthy of life", a more specific term which originally referred to the severely disabled who were involuntarily euthanised in Aktion T4, and was eventually applied to the extermination of the Jews. That policy of euthanasia started officially on 1 September 1939 when Hitler signed an edict to the effect, and carbon monoxide was first used to murder disabled patients. The same gas was used in the death camps such as Treblinka, although they used engine exhaust gases to achieve the same end. In directive No. 1306 by Reich Ministry of Public Enlightenment and Propaganda from 24 October 1939, the term "Untermensch" is used in reference to Polish ethnicity and culture, as follows:

It must become clear to everybody in Germany, even to the last milkmaid, that Polishness is equal to subhumanity. Poles, Jews and Gypsies are on the same inferior level. This must be clearly outlined [...] until every citizen of Germany has it encoded in his subconsciousness that every Pole, whether a farm worker or intellectual, should be treated like vermin.

Biology classes in Nazi-era Germany schools taught about differences between the race of Nordic German "Übermenschen" and "ignoble" Jewish and Slavic "subhumans". The view that Slavs were subhuman was widespread among the German masses, and chiefly applied to the Poles. It continued to find support after the war.

Chronobiology

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Chronobiology 

Overview, including some physiological parameters, of the human circadian rhythm ("biological clock")

Chronobiology is a field of biology that examines timing processes, including periodic (cyclic) phenomena in living organisms, such as their adaptation to solar- and lunar-related rhythms. These cycles are known as biological rhythms. Chronobiology comes from the ancient Greek 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 rhythms. Other aspects include epigenetics, development, reproduction, ecology and evolution.

Subject

Chronobiology studies variations of the timing and duration of biological activity in living organisms which occur for many essential biological processes. These occur in animals (eating, sleeping, mating, hibernating, migration, cellular regeneration, etc.), in plants (leaf movements, photosynthetic reactions, etc.), as well as in microbial organisms such as fungi and protozoa. They have also been found in bacteria, especially among the cyanobacteria (blue-green algae). 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." The circadian rhythm is regulated by circadian clocks, which are biochemical mechanisms that regulate physiological processes based on time of day.

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:

• 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, 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, such as lunar rhythms in marine life being dictated by the lunar cycle.

Many other important cycles are also studied, including:

• Infradian rhythms, which are cycles longer than a day. Examples include circannual or annual cycles that govern migration or reproduction cycles in many plants and animals, or the human menstrual cycle.
• Ultradian rhythms, 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.
• 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 acrophase. When the process is less active, the cycle is in its 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. In 1751, Swedish botanist and naturalist Carl Linnaeus (Carl von Linné) designed a flower clock using certain species of flowering plants. 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 hawk's beard plant which opened its flowers at 6:30 am and the hawkbit which did not open its flowers until 7 am.

The 1960 symposium at Cold Spring Harbor Laboratory laid the groundwork for the field of chronobiology.

It was also in 1960 that Patricia DeCoursey invented the phase response curve while studying light response in rodents, 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 and fruit flies.

The role of Retinal Ganglion cells

Melanopsin as a circadian photopigment

In 2002, 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 biological clock to daily light-dark cycles. He also described the role of melanopsin in ipRGCs. Using a rat melanopsin gene, a melanopsin-specific antibody, and 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 mammals. 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.

Melanopsin cells relay inputs from rods and cones

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. In 2008, Hattar and his research team transplanted diphtheria toxin genes into the mouse melanopsin gene locus to create 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.

Distinct ipRGCs

Further research has shown that ipRGCs project to different brain nuclei to control both non-image forming and image forming functions. These brain regions include the SCN, where input from ipRGCs is necessary to photoentrain circadian rhythms, and the olivary pretectal nucleus (OPN), where input from ipRGCs control the pupillary light reflex. Hattar and colleagues conducted research that demonstrated that ipRGCs project to hypothalamic, thalamic, stratal, brainstem and limbic structures. Although ipRGCs were initially viewed as a uniform population, further research revealed that there are several subtypes with distinct morphology and physiology. Since 2011, Hattar's laboratory has contributed to these findings and has successfully distinguished subtypes of ipRGCs.

Diversity of ipRGCs

Hattar and colleges utilized Cre-based strategies for labeling ipRGCs to reveal that there are at least five ipRGC subtypes that project to a number of central targets. 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.

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 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 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. 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.

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 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-like symptoms and lead to impaired learning in mice, independent of sleep and circadian oscillations.

Effect on mood

ipRGCs project to areas of the brain that are important for regulating circadian rhythmicity and sleep, most notably the 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, lateral habenula, and subparaventricular nucleus further implicating light's possible influence on mood and other cognitive functions.

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 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.

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 memories into 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 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 (TBS). Recognition memory was also affected, with T7 mice failing to show preference for novel objects in the novel object recognition test.

Necessity of ipRGCs

Mice without (Opn4^aDTA/aDTA 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.

Research developments

Light and melatonin

More recently, light therapy and 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.

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 of the circadian system by light (parametric, continuous, tonic, gradual vs. nonparametric, discrete, phasic, instantaneous, respectively).

Chronotypes

Humans can have a propensity to be morning people or evening people; these behavioral preferences are called chronotypes for which there are various assessment questionnaires and biological marker correlations.

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.

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. A followup study appeared on Chronobiology International in 2021 showed that these patterns were not disrupted by the 2020 UK lockdown.

Modulators of circadian rhythms

In 2021, scientists reported the development of a light-responsive days-lasting modulator of circadian rhythms of tissues via Ck1 inhibition. Such modulators may be useful for chronobiology research and repair of organs that are "out of sync".

Neurological disorders

In 2021, scientists found that children with autism spectrum disorder are more likely to have disruptions in their sleep-wake cycle. Additionally, children with autism were also found more likely to have abnormal daily hormone cycles of cortisol, melatonin, and serotonin compared to the average person.

A 2017 study found that people with Attention deficit hyperactivity disorder (ADHD) often have a delayed sleep phase in their circadian rhythm, meaning that they go to sleep later than the average person. An earlier study from 2013 found similar results to the 2017 study, but also found a correlation between Seasonal affective disorder, ADHD, and sleeping problems.

Physical diseases and disorders

In 2015, a study on the frequency of gout attacks found that they occur over twice as often in the night and early morning than other times of day. A 2021 study on osteoporosis found that disruption of circadian rhythms (such as working night shifts) can lead to osteoporosis by disturbing bone remodeling that typically happens at night.

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.