Sleep-learning

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Sleep-learning 

 

Sleep-learning (also known as hypnopædia, or hypnopedia) is an attempt to convey information to a sleeping person, typically by playing a sound recording to them while they sleep. Although often used in pop culture as a way to introduce new information (see 'In Fiction'), sleep is considered an important period for memory consolidation.

Although learning new information during sleep has not been considered possible, at least to the extent it is used in fiction, the term hypnopedia has also been used to refer to the technique of exposing someone to sounds or odors during sleep in attempts to boost memory for previously learned information. Hypnopedia, in this sense, is related to a technique now known as Targeted Memory Reactivation (TMR). Unlike the pop-culture idea of sleep-learning, or learning new information during sleep, TMR pairs newly acquired information with sounds that can later be played, or cued, during electroencephalography (EEG) verified sleep to strengthen memory. This type of sleep reactivation in humans has been found successful in strengthening memory in a number of different paradigms including language learning, motor-skill learning, and spatial memory. Research in TMR has shown that cueing sounds that are associated with previously learned material over a period of sleep is more beneficial to memory than a similar period of wake. Likewise, cued material is also better preserved than material that is not cued during sleep.

History

In 1927, Alois Benjamin Saliger invented the Psycho-Phone for sleep learning, stating that "It has been proven that natural sleep is identical with hypnotic sleep and that during natural sleep the unconscious mind is most receptive to suggestions."

Since the electroencephalography studies by Charles W. Simon and William H. Emmons in 1956, learning by sleep has not been taken seriously. The researchers concluded that learning during sleep was "impractical and probably impossible". They reported that stimulus material presented during sleep was not recalled later when the subject awoke unless alpha wave activity occurred at the same time the stimulus material was given.

The idea of reactivating memories in humans to improve memory began with the finding that neurons active in the hippocampus in rodents were found to fire together during subsequent sleep.

In 2012, research from the Weizmann Institute of Science indicated that classical conditioning can occur during sleep by using odor recognition. "During sleep, humans can strengthen previously acquired memories, but whether they can acquire entirely new information remains unknown. The nonverbal nature of the olfactory sniff response, in which pleasant odors drive stronger sniffs and unpleasant odors drive weaker sniffs, allowed us to test learning in humans during sleep."

In fiction

The idea of sleep-learning is found in influential science fiction and other literature. The following examples are listed chronologically by publication or original air date, when known.

• In Hugo Gernsback's 1911 story Ralph 124C 41+, one finds the Hypnobioscope, a sleep learning device.
• In Aldous Huxley's 1932 novel Brave New World, it is used for the conditioning of children into the novel's fictional future culture. In the novel, sleep-learning was discovered by accident when a Polish boy named Reuben Rabinovitch was able to recite an entire radio broadcast in English after a radio receiver was left on in his sleep. The boy was unable to comprehend what he had heard via hypnopædia, but it was soon realized that hypnopædia could be used to effectively make suggestions about morality.
• In Robert Heinlein's 1948 novel Space Cadet, the character Matt Dodson is taught to speak Venutian (the language of the planet Venus) while under drug-aided hypnosis. He surprises his Venus-born friend Oscar by spontaneously reproving him when Oscar utters a curse in Venutian. (Later in the novel Matt appears to have forgotten what he learned and relies on Oscar for translation.)
• In the BBC Radio series Journey into Space (1953–1958), during the second and third parts of the trilogy, there were said to be Martians abducting people from the Earth and conditioning them to obey instructions or to make them believe things that were not true. The inception of this conditioning involved putting the subject into a hypnotic sleep and appraising them of a certain situation; once they awoke they would believe it, regardless of the validity.
• In a 1961 episode of My Three Sons, "A Lesson In Any Language", Mike connects a phonograph to an automatic timer to play Spanish lessons while he sleeps. Steve and Bub ultimately end up sleeping in the room and are able to speak fluent Spanish the following day.
• In Anthony Burgess's 1962 novel A Clockwork Orange, it is used to reverse the effects of the Ludovico Technique, a form of classical conditioning, which was used on the main character Alex to make him incapable of violent behavior. The conditioning was a new technique which was supposed to rehabilitate violent criminals in a short period of time, but which resulted in Alex attempting to commit suicide. This reflected very badly on the government, which had sanctioned the experiment, so hypnopædia was used to undo the conditioning.
• In 1954 Günter Spang wrote a children's book called Lohengrin schwant etwas, meaning Lohengrin has a good idea, in which a bunch of schoolchildren take an easy way out of studying by learning in their sleep.
• In a 1963 episode of The Patty Duke Show, "The Conquering Hero", Cathy tries to help a failing basketball player pass a quiz. She suggests that the latest scientific method of "subconscious learning" will help. She records the lessons on a tape which plays repeatedly while he is asleep. He passes the quiz after the answers "come to him" while looking at the questions.
• In the 1965 episode of "I Spy" titled Chrysanthemum, the assigned partner of Bill Cosby and Robert Culp's characters, Maximilian de Broget claims to have learned Mandarin Chinese in his sleep.
• In the 1965 movie The Monkey's Uncle, a college student connects a phonograph to an automatic timer, which plays to sleeping students the voice of a girl reading their lessons aloud. This backfires in class, however—when asked to give an oral report, the students speak, but in the girl's voice.
• In the 1966 novel Flowers for Algernon, an intellectually disabled 37-year-old, Charlie Gordon, has an operation to increase his intelligence. Professor Nemur and Dr. Strauss then give Charlie a "teeching mashine that werks like T.V." Charlie explains to Professor Nemur that "I dint think I was goin to get smart anyway" [sic].
• The 1976 film Logan's Run contains a scene where Logan 5 (Michael York) chastises his friend Francis 7 (Richard Jordan) for his rigidly orthodox opinions, "You sound like a sleep-teacher with a stuck tape".
• In a 1988 episode of the BBC2 sitcom Red Dwarf, "Me²", Arnold Rimmer uses sleep-learning tapes such as Learn Esperanto While You Sleep and Learn Quantum Theory While You Sleep, to the dismay of his bunkmate Dave Lister.
• In the 1990 movie Dragon Ball Z: The Tree of Might, Chi-Chi packs for her son Gohan a tape recorder so he can learn while he sleeps on a camping trip.
• In a 1992 episode of The Simpsons, "Bart's Friend Falls in Love", Homer orders hypnosis tapes which are supposed to induce weight loss. However, the mail-order company sends him vocabulary builder tapes instead, and Homer gets fatter and fatter while his vocabulary increases, through hypnopædia.
• In a 1996 episode of Dexter's Laboratory, "The Big Cheese", Dexter hooks himself up to a gramophone that repeats his lesson for a French class test the next morning. The gramophone gets stuck at the phrase omelette du fromage, and Dexter finds out the next morning that it is all he is capable of saying.
• In a 1997 of Friends, "The One with the Hypnosis Tape", Chandler borrows from Rachel a smoking-cessation audiocassette, to which he listens while he is asleep. The tape tells him that he is "a strong, confident woman" who does not need to smoke. He stops smoking, but also begins acting effeminately.
• In a 2001 episode of Homestar Runner, "A Jorb Well Done", Coach Z attempts to overcome his speech impediment with the word "job" (which he pronounces as "jorb"). After unsuccessfully trying several methods, Strong Sad gives him a tape of him repeating the word job thousands of times, "from when (he) was practicing the dictionary". Coach Z takes it home and listens to it while he sleeps, and the next day is able to pronounce "job" correctly, but forgets Homestar's name.
• The twins Hank and Dean Venture, of the animated television program The Venture Bros., are homeschooled through the use of hypnopædic beds.
• In the 1997 PC game Outpost 2: Divided Destiny, one of the items available for research was hypnopædia, which allowed scientists to be trained more quickly.

Sleep and learning

From Wikipedia, the free encyclopedia

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

 

Multiple hypotheses explain the possible connections between sleep and learning in humans. Research indicates that sleep does more than allow the brain to rest. It may also aid the consolidation of long-term memories.

REM sleep and slow-wave sleep play different roles in memory consolidation. REM is associated with the consolidation of nondeclarative (implicit) memories. An example of a nondeclarative memory would be a task that we can do without consciously thinking about it, such as riding a bike. Slow-wave, or non-REM (NREM) sleep, is associated with the consolidation of declarative (explicit) memories. These are facts that need to be consciously remembered, such as dates for a history class.

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. Current studies demonstrate that a healthy sleep produces a significant learning-dependent performance boost. 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. 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.

Healthy sleep must include the appropriate sequence and proportion of NREM and REM phases, 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. 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. In motor skill learning, an interval of sleep may be critical for the expression of performance gains; without sleep these gains will be delayed.

Procedural memories are a form of nondeclarative memory, so they would most benefit from the fast-wave REM sleep. In a study, procedural memories have been shown to benefit from sleep. 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.

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. A study 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. 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.

Research has shown that taking an afternoon nap increases learning capacity. A study  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. A more recent study 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.

Electrophysiological evidence in rats

A 2009 study based on electrophysiological recordings of large ensembles of isolated cells in the prefrontal cortex of rats revealed that cell assemblies that formed upon learning were more preferentially active during subsequent sleep episodes. More specifically, those replay events were more prominent during slow wave sleep and were concomitant with hippocampal reactivation events. This study has shown that neuronal patterns in large brain networks are tagged during learning so that they are replayed, and supposedly consolidated, during subsequent sleep. There have been other studies that have shown similar reactivation of learning pattern during motor skill and neuroprosthetic learning. Notably, new evidence is showing that reactivation and rescaling may be co-occurring during sleep.

Sleep in relation to school

Sleep has been directly linked to the grades of students. One in four U.S. high school students admit to falling asleep in class at least once a week. Consequently, results have shown that those who sleep less do poorly. In the United States, sleep deprivation is common with students because almost all schools begin early in the morning and many of these students either choose to stay awake late into the night or cannot do otherwise due to delayed sleep phase syndrome. As a result, students that should be getting between 8.5 and 9.25 hours of sleep are getting only 7 hours. Perhaps because of this sleep deprivation, their grades are lower and their concentration is impaired.

As a result of studies showing the effects of sleep deprivation on grades, and the different sleep patterns for teenagers, a school in New Zealand, changed its start time to 10:30 a.m., in 2006, to allow students to keep to a schedule that allowed more sleep. In 2009, Monkseaton High School, in North Tyneside, had 800 pupils aged 13–19 starting lessons at 10 a.m. instead of the normal 9 a.m. and reported that general absence dropped by 8% and persistent absenteeism by 27%. Similarly, a high school in Copenhagen has committed to providing at least one class per year for students who will start at 10 a.m. or later.

College students represent one of the most sleep-deprived segments of our population. Only 11% of American college students sleep well, and 40% of students feel well rested only two days per week. About 73% have experienced at least some occasional sleep issues. This poor sleep is thought to have a severe impact on their ability to learn and remember information because the brain is being deprived of time that it needs to consolidate information which is essential to the learning process.

Mohave people

From Wikipedia, the free encyclopedia

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

 

Mojave People

Henry Welshe, Mojave tribal chairman of Colorado River Indian Reservation council, ca. 1944–6
Total population
2,000 (Golla, 2007)–967 (1990)
Regions with significant populations
United States ( Arizona)
Languages
Mojave, English
Religion
traditional tribal religion, Humatuve
Related ethnic groups
Maricopa, Walapai, Havasupai, and Yavapai

Mohave or Mojave (Pronounced "Moh-ha-vee")(Mojave: 'Aha Makhav) are a Native American people indigenous to the Colorado River in the Mojave Desert. The Fort Mojave Indian Reservation includes territory within the borders of California, Arizona, and Nevada. The Colorado River Indian Reservation includes parts of California and Arizona and is shared by members of the Chemehuevi, Hopi, and Navajo peoples.

The original Colorado River and Fort Mojave reservations were established in 1865 and 1870, respectively. Both reservations include substantial senior water rights in the Colorado River; water is drawn for use in irrigated farming.

The four combined tribes sharing the Colorado River Indian Reservation function today as one geo-political unit known as the federally recognized Colorado River Indian Tribes; each tribe also continues to maintain and observe its individual traditions, distinct religions, and culturally unique identities.

Culture

Mohave ceramic figurine with red slip and earrings, pre-1912, Peabody Museum of Archaeology and Ethnology

 

In the 1930s, George Devereux, a Hungarian-French anthropologist, did fieldwork and lived among the Mohave for an extended period of study. He published extensively about their culture and incorporated psychoanalytic thinking in his interpretation of their culture.

Language

The Mojave language belongs to the River Yuman branch of the Yuman language family. In 1994 approximately 75 people in total on the Colorado River and Fort Mojave reservations spoke the language, according to linguist Leanne Hinton. The tribe has published language materials, and there are new efforts to teach the language to their children.

Religion

The Mohave creator is Matevilya, who gave the people their names and their commandments. His son is Mastamho, who gave them the River and taught them how to plant. Historically this was an agrarian culture; they planted in the fertile floodplain of the untamed river, following the age-old customs of the Aha cave. They have traditionally used the indigenous plant Datura as a deliriant hallucinogen in a religious sacrament. A Mohave who is coming of age must consume the plant in a rite of passage, in order to enter a new state of consciousness.

History

1851 drawing of Mohavi men and women made by Lorenzo Sitgreaves' topographical mission across Arizona in 1851.

 

Chiefs Irataba and Cairook, with Mohave woman, by Balduin Möllhausen (1856)

Much of early Mojave history remains unrecorded in writing, since the Mojave language was not written in precolonial times. They depended on oral communication to transmit their history and culture from one generation to the next. Disease, outside cultures and encroachment on their territory disrupted their social organization. Together with having to adapt to a majority culture of another language, this resulted in interrupting the Mojave transmission of their stories and songs to the following generations.

The tribal name has been spelled in Spanish and English transliteration in more than 50 variations, such as Hamock avi, Amacava, A-mac-ha ves, A-moc-ha-ve, Jamajabs, and Hamakhav. This has led to misinterpretations of the tribal name, also partly traced to a translation error in Frederick W. Hodge's 1917 Handbook of the American Indians North of Mexico (1917). This incorrectly defined the name Mohave as being derived from hamock, (three), and avi, (mountain). According to this source, the name refers to the mountain peaks known as The Needles in English, located near the Colorado River. (The city of Needles, California is located a few miles north from here). But, the Mojave call these peaks Huqueamp avi, which means "where the battle took place," referring to the battle in which the God-son, Mastamho, slew the sea serpent.

Ancestral lands

Charley-Arri-Wa-Wa (Mohave), 1872

The Mojave held lands along the river that stretched from Black Canyon, where the tall pillars of First House of Mutavilya loomed above the river, past Avi kwame or Spirit Mountain, the center of spiritual things, to the Quechan Valley, where the lands of other tribes began. As related to contemporary landmarks, their lands began in the north at Hoover Dam and ended about one hundred miles below Parker Dam on the Colorado River, or aha kwahwat in Mojave.

19th–20th centuries

Mosa (Mojave girl), 1903, photograph by Edward Curtis

In mid-April 1859, United States troops, led by Lieutenant Colonel William Hoffman, on the Expedition of the Colorado, moved upriver into Mojave country with the well-publicized objective of establishing a military post. By this time, white immigrants and settlers had begun to encroach on Mojave lands and the post was intended to protect east-west European-American emigrants from attack by the Mojave. Hoffman sent couriers among the tribes, warning that the post would be gained by force if they or their allies chose to resist. During this period, several members of the Rose party were massacred by the Mojave. The Mojave warriors withdrew as Hoffman's armada approached and the army, without conflict, occupied land near the future Fort Mojave. Hoffman ordered the Mojave men to assemble on April 23, 1859 at the armed stockade adjacent to his headquarters, to hear Hoffman' terms of peace. Hoffman gave them the choice of submission or extermination and the Mojave chose submission. At that time the Mojave population was estimated to be about 4,000 which were comprised into 22 clans identified by totems. 

Two Mojave girls standing in front of a small dwelling with a thatched roof, 1900

 

Under American law the Mohave were to live on the Colorado River Reservation after its establishment in 1865; however many refused to leave their ancestral homes in the Mojave Valley. At this time, under jurisdiction of the War Department, officials declined to try to force them onto the reservation and the Mojave in the area were relatively free to follow their tribal ways. In the midsummer of 1890, after the end of the Indian Wars, the War Department withdrew its troops and the post was transferred to the Office of Indian Affairs within the Department of the Interior.

Beginning in August 1890, the Office of Indian Affairs began an intensive program of assimilation where Mohave, and other native children living on reservations, were forced into boarding schools in which they learned to speak, write, and read English. This assimilation program, which was Federal policy, was based on the belief that this was the only way native peoples could survive. Fort Mojave was converted into a boarding school for local children and other "non-reservation" Indians. Until 1931, forty-one years later, all Fort Mojave boys and girls between the ages of six and eighteen were compelled to live at this school or to attend an advanced Indian boarding school far removed from Fort Mojave.

Two Mojave Indian women playing a game (fortune-telling with bones?), ca.1900

 

The assimilation helped to break up tribal culture and governments. In addition to English, schools taught American culture and customs and insisted that the children follow them; students were required to adopt European-American hairstyles (which included hair cutting), clothing, habits of eating, sleeping, toiletry, manners, industry, and language. Use of their own language or customs was a punishable offense; at Fort Mojave five lashes of the whip were issued for the first offense. Such corporal punishment of children scandalized the Mojave, who did not discipline their children in that way.

As part of the assimilation the administrators assigned English names to the children and registered as members of one of two tribes, the Mojave Tribe on the Colorado River Reservation and the Fort Mojave Indian Tribe on the Fort Mojave Indian Reservation. These divisions did not reflect the traditional Mojave clan and kinship system. By the late 1960s, thirty years after the end of the assimilation program 18 of the 22 traditional clans had survived.

Population

Estimates of the pre-contact populations of most native groups in California have varied substantially. Alfred L. Kroeber (1925:883) put the 1770 population of the Mohave at 3,000 and Francisco Garcés, a Franciscan missionary-explorer, also estimated the population at 3,000 in 1776(Garcés 1900(2):450).

A.L. Kroeber estimate of the population in 1910 was 1,050. By 1963 Lorraine M. Sherer's research revealed the population had shrunk to approximately 988, with 438 at Fort Mojave and 550 of the Colorado River Reservation.

Current status

The Mohave, along with the Chemehuevi, some Hopi, and some Navajo, share the Colorado River Indian Reservation and function today as one geopolitical unit known as the federally recognized Colorado River Indian Tribes; each tribe also continues to maintain and observe its individual traditions, distinct religions, and culturally unique identities. The Colorado River Indian Tribes headquarters, library and museum are in Parker, Arizona, about 40 miles (64 km) north of I-10. The Colorado River Indian Tribes Native American Days Fair & Expo is held annually in Parker, from Thursday through Sunday during the first week of October. The Megathrow Traditional Bird Singing & Dancing social event is also celebrated annually, on the third weekend of March. RV facilities are available along the Colorado River.

Slow-wave sleep

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Slow-wave_sleep 

Ostriches sleeping, with REM and slow-wave sleep phases

 

Slow-wave sleep (SWS), often referred to as deep sleep, consists of stage three of non-rapid eye movement sleep. Initially, SWS consisted of both Stage 3, which has 20–50 percent delta wave activity, and Stage 4, which has more than 50 percent delta wave activity.

Overview

This period of sleep is called slow-wave sleep because the EEG activity is synchronized, producing slow waves with a frequency range of 0.5–2 Hz and peak-to-peak amplitude greater than 75µV. The first section of the wave signifies a "down state", which is an inhibition or hyperpolarizing phase in which the neurons in the neocortex are silent. This is the period when the neocortical neurons are able to rest. The second section of the wave signifies an "up state", which is an excitation or depolarizing phase in which the neurons fire briefly at a high rate. The principal characteristics during slow-wave sleep that contrast with REM sleep are moderate muscle tone, slow or absent eye movement, and lack of genital activity.

Slow-wave sleep is considered important for memory consolidation. This is sometimes referred to as "sleep-dependent memory processing". Impaired memory consolidation has been seen in individuals with primary insomnia who thus do not perform as well as those who are healthy in memory tasks following a period of sleep. Furthermore, slow-wave sleep improves declarative memory (which includes semantic and episodic memory). A central model has been hypothesized that the long-term memory storage is facilitated by an interaction between the hippocampal and neocortical networks. In several studies, after the subjects have had training to learn a declarative memory task, the density of human sleep spindles present was significantly higher than the signals observed during the control tasks that involved similar visual stimulation and cognitively-demanding tasks but did not require learning. This associated with the spontaneously occurring wave oscillations that account for the intracellular recordings from thalamic and cortical neurons.

Specifically, SWS presents a role in spatial declarative memory. Reactivation of the hippocampus during SWS is detected after the spatial learning task. In addition, a correlation can be observed between the amplitude of hippocampal activity during SWS and the improvement in spatial memory performance, such as route retrieval, on the following day.

A memory reactivation experiment during SWS was conducted using odor as a cue, given that it does not disturb ongoing sleep, over a prior learning task and sleep sessions. The region of the hippocampus was activated in response to odor re-exposure during SWS. This stage of sleep has an exclusive role as a context cue that reactivates the memories and favors their consolidation. A further study demonstrated that when subjects heard sounds associated with previously shown pictures-locations, the reactivation of individual memory representations was significantly higher during SWS compared to other sleep stages.

Affective representations are generally better remembered during sleep compared to neutral ones. Emotions with negative salience presented as a cue during SWS show better reactivation, therefore an enhanced consolidation in comparison to neutral memories. The former was predicted by sleep spindles over SWS, which discriminates the memory processes during sleep as well as facilitating emotional memory consolidation.

Acetylcholine plays an essential role in hippocampus-dependent memory consolidation. An increased level of cholinergic activity during SWS is known to be disruptive for memory processing. Considered that acetylcholine is a neurotransmitter that modulates the direction of information flow between the hippocampus and neocortex during sleep, its suppression is necessary during SWS in order to consolidate sleep-related declarative memory.

Sleep deprivation studies with humans suggest that the primary function of slow-wave sleep may be to allow the brain to recover from its daily activities. Glucose metabolism in the brain increases as a result of tasks that demand mental activity. Another function affected by slow-wave sleep is the secretion of growth hormone, which is always greatest during this stage. It is also thought to be responsible for a decrease in sympathetic and increase in parasympathetic neural activity.

Prior to 2007 the American Academy of Sleep Medicine (AASM) divided Slow-wave sleep into stages 3 and 4. The two stages are now combined as "Stage three" or N3. An epoch (30 seconds of sleep) which consists of 20% or more slow-wave (delta) sleep is now considered to be stage three.

Electroencephalographic characteristics

Polysomnogram demonstrating SWS, stage four.
 

High amplitude EEG is highlighted in red.

Large 75-microvolt (0.5–2.0 Hz) delta waves predominate the electroencephalogram (EEG). Stage N3 is defined by the presence of 20% delta waves in any given 30-second epoch of the EEG during sleep, by the current 2007 AASM guidelines.

Longer periods of SWS occur in the first part of the night, primarily in the first two sleep cycles (roughly three hours). Children and young adults will have more total SWS in a night than older adults. The elderly may not go into SWS at all during many nights of sleep.

Slow-wave sleep is an active phenomenon probably brought about by the activation of serotonergic neurons of the raphe system.

The slow-wave seen in the cortical EEG is generated through thalamocortical communication through the thalamocortical neurons. In the TC neurons this is generated by the "slow oscillation" and is dependent on membrane potential bistability, a property of these neurons due to an electrophysiological component known as "I t window". "I t window" is due to the overlap underneath activation and inactivation curves if plotted for T-type calcium channels (inward current). If these two curves are multiplied, and another line superimposed on the graph to show a small Ik leak current (outward), then the interplay between these inward (I t window) and outward (small Ik leak), three equilibrium points are seen at −90, −70 and −60 mv, −90 and −60 being stable and −70 unstable. This property allows the generation of slow waves due to an oscillation between two stable points. It is important to note that in in vitro, mGluR must be activated on these neurons to allow a small Ik leak, as seen in in vivo situations.

Functions

Hemispheric asymmetries in the human sleep

Slow-wave sleep is necessary for survival. Some animals, such as dolphins and birds, have the ability to sleep with only one hemisphere of the brain, leaving the other hemisphere awake to carry out normal functions and to remain alert. This kind of sleep is called unihemispheric slow-wave sleep and it is also partially observable in human beings. Indeed, a study reported a unilateral activation of the somatosensorial cortex when a vibrating stimulus was put on the hand of human subjects. The recordings show an important inter-hemispheric change during the first hour of non-REM sleep and consequently the presence of a local and use-dependent aspect of sleep. Another experiment detected a greater number of delta waves in the frontal and central regions of the right hemisphere.

Considering that SWS is the only sleep stage that reports human deep sleep as well as being used in studies with mammals and birds, it is also adopted in experiments revealing the role of hemispheric asymmetries during sleep. A predominance of the left hemisphere in the neural activity can be observed in the default-mode network during SWS. This asymmetry is correlated with the sleep-onset-latency, which is a sensitive parameter of the so-called first night effect, in other words of the reduced quality of sleep during the first session in the laboratory.

The left hemisphere is shown to be more sensitive to deviant stimuli during the first night compared to the following nights of an experiment. This asymmetry explains further the reduced sleep of half the brain during SWS. Indeed, in comparison to the right one, the left hemisphere plays a vigilant role during SWS.

Furthermore, a faster behavioral reactivity is detected in the left hemisphere during SWS of the first night. The rapid awakening is correlated to the regional asymmetry in the activities of SWS. These findings show that the hemispheric asymmetry in SWS plays a role as a protective mechanism. SWS is therefore sensitive to danger and non-familiar environment, creating a need for vigilance and reactivity during sleep.

Neural control of slow-wave sleep

Several neurotransmitters are involved in sleep and waking patterns: acetylcholine, norepinephrine, serotonin, histamine, and orexin. Neocortical neurons fire spontaneously during slow-wave sleep, thus they seem to play a role during this period of sleep. Also, these neurons appear to have some sort of internal dialogue, which accounts for the mental activity during this state where there is no information from external signals because of the synaptic inhibition at the thalamic level. The rate of recall of dreams during this state of sleep is relatively high compared to the other levels of the sleep cycle. This indicates that mental activity is closer to real life events.

Physical healing and growth

Slow-wave sleep is the constructive phase of sleep for recuperation of the mind-body system in which it rebuilds itself after each day. Substances that have been ingested into the body while an organism is awake are synthesized into complex proteins of living tissue. Growth hormones are also secreted to facilitate the healing of muscles as well as repairing damage to any tissues. Lastly, glial cells within the brain are restored with sugars to provide energy for the brain.

Learning and synaptic homeostasis

Learning and memory formation occurs during wakefulness by the process of long-term potentiation; SWS is associated with the regulation of synapses thus potentiated. SWS has been found to be involved in the downscaling of synapses, in which strongly stimulated or potentiated synapses are kept while weakly potentiated synapses either diminish or are removed. This may be helpful for recalibrating synapses for the next potentiation during wakefulness and for maintaining synaptic plasticity. Notably, new evidence is showing that reactivation and rescaling may be co-occurring during sleep.

Problems associated with slow-wave sleep

Bedwetting, night terrors, and sleepwalking are all common behaviors that can occur during stage three of sleep. These occur most frequently amongst children, who then generally outgrow them. Another problem that may arise is sleep-related eating disorder. An individual will sleep-walk leaving his or her bed in the middle of the night seeking out food, and will eat not having any memory of the event in the morning. Over half of individuals with this disorder become overweight. Sleep-related eating disorder can usually be treated with dopaminergic agonists, or topiramate, which is an anti-seizure medication. This nocturnal eating throughout a family suggests that heredity may be a potential cause of this disorder.

Effects of sleep deprivation

J. A. Horne (1978) reviewed several experiments with humans and concluded that sleep deprivation has no effects on people’s physiological stress response or ability to perform physical exercise. It did, however, have an effect on cognitive functions. Some people reported distorted perceptions or hallucinations and lack of concentration on mental tasks. Thus, the major role of sleep does not appear to be rest for the body, but rest for the brain.

When sleep-deprived humans sleep normally again, the recovery percentage for each stage of sleep is not the same. Only seven percent of stages one and two are regained, but 68 percent of stage-four slow-wave sleep and 53 percent of REM sleep are regained. This suggests that stage-four sleep (known today as the deepest part of stage-three sleep) is more important than the other stages.

During slow-wave sleep, there is a significant decline in cerebral metabolic rate and cerebral blood flow. The activity falls to about 75 percent of the normal wakefulness level. The regions of the brain that are most active when awake have the highest level of delta waves during slow-wave sleep. This indicates rest is geographical. The “shutting down” of the brain accounts for the grogginess and confusion if someone is awakened during deep sleep since it takes the cerebral cortex time to resume its normal functions.

According to J. Siegel (2005), sleep deprivation results in the build-up of free radicals and superoxides in the brain. Free radicals are oxidizing agents that have one unpaired electron, making them highly reactive. These free radicals interact with electrons of biomolecules and damage cells. In slow-wave sleep, the decreased rate of metabolism reduces the creation of oxygen byproducts, thereby allowing the existing radical species to clear. This is a means of preventing damage to the brain.

Amyloid-beta pathology

The accumulation of Amyloid beta (Aβ) in the prefrontal cortex is associated with the disruption or reduction of slow waves of NREM sleep. Therefore, this may reduce the ability for memory consolidation in older adults.

Individual differences

Though SWS is fairly consistent within the individual, it can vary across individuals. Age and gender have been noted as two of the biggest factors that affect this period of sleep. Aging is inversely proportional to the amount of SWS beginning by midlife and therefore, SWS declines with age. Sex differences have also been found, such that females tend to have higher levels of SWS compared to males, at least up until menopause. There have also been studies that have shown differences between races. The results showed that there was a lower percentage of SWS in African Americans compared to Caucasians, but since there are many influencing factors (e.g. body mass index, sleep-disordered breathing, obesity, diabetes, and hypertension) this potential difference must be investigated further.

Mental disorders play a role in individual differences in the quality and quantity of SWS: subjects suffering from depression show a lower amplitude of slow-wave activity compared to healthy participants. Sex differences also persist in the former group: depressed men present significantly lower SWA amplitude. This sex divergence is twice as large as the one observed in healthy subjects. However, no age-related difference concerning SWS can be observed in the depressed group.

Brain regions

Some of the brain regions implicated in the induction of slow-wave sleep include:

• the parafacial zone (GABAergic neurons), located within the medulla oblongata
• the nucleus accumbens core (GABAergic medium spiny neurons; specifically, the subset of these neurons that expresses both D2-type dopamine receptors and adenosine A_2A receptors), located within the striatum
• the ventrolateral preoptic area (GABAergic neurons), located within the hypothalamus
• the lateral hypothalamus (melanin-concentrating hormone-releasing neurons), located within the hypothalamus

Drugs

The chemical gamma-hydroxybutyric acid (GHB) has been studied to increase SWS. In the United States, the Food and Drug Administration (FDA) permits the use of GHB under the trade name Xyrem to reduce cataplexy attacks and excessive daytime sleepiness in patients with narcolepsy.

Trazodone is also being investigated in connection with improving non-REM slow-wave sleep, and related reductions in Alzheimer's-related buildup of amyloid and tau.

Exploding head syndrome

From Wikipedia, the free encyclopedia

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

 

Exploding head syndrome
Other names	Episodic cranial sensory shock, snapping of the brain, auditory sleep start
Artistic depiction of flash seen from exploding head syndrome
Specialty	Sleep medicine
Symptoms	Hearing loud noises when falling asleep or waking up
Duration	Short
Causes	Unknown
Differential diagnosis	Nocturnal epilepsy, hypnic headaches, nightmare disorder, PTSD
Treatment	Reassurance, clomipramine, calcium channel blockers
Prognosis	Good
Frequency	~10% of people

Exploding head syndrome (EHS) is a condition in which a person experiences unreal noises that are loud and of short duration when falling asleep or waking up. The noise may be frightening, typically occurs only occasionally, and is not a serious health concern. People may also experience a flash of light. Pain is typically absent.

The cause is unknown. Potential explanations include ear problems, temporal lobe seizure, nerve dysfunction, or specific genetic changes. Potential risk factors include psychological stress. It is classified as a sleep disorder or headache disorder. People often go undiagnosed.

There is no high quality evidence to support treatment. Reassurance may be sufficient. Clomipramine and calcium channel blockers have been tried. While the frequency of the condition is not well studied, some have estimated that it occurs in about 10% of people. Females are reportedly more commonly affected. The condition was initially described at least as early as 1876. The current name came into use in 1988.

Signs and symptoms

Individuals with exploding head syndrome hear or experience loud imagined noises as they are falling asleep or waking up, have a strong, often frightened emotional reaction to the sound, and do not report significant pain; around 10% of people also experience visual disturbances like perceiving visual static, lightning, or flashes of light. Some people may also experience heat, strange feelings in their torso, or a feeling of electrical tinglings that ascends to the head before the auditory hallucinations occur. With the heightened arousal, people experience distress, confusion, myoclonic jerks, tachycardia, sweating, and the sensation that feels as if they have stopped breathing and have to make a deliberate effort to breathe again.

The pattern of the auditory hallucinations is variable. Some people report having a total of two or four attacks followed by a prolonged or total remission, having attacks over the course of a few weeks or months before the attacks spontaneously disappear, or the attacks may even recur irregularly every few days, weeks, or months for much of a lifetime.

Some individuals hold the belief that EHS episodes are not natural events, but are the effects of directed energy weapons which create an auditory effect.^[9] Thus, EHS has been worked into conspiracy theories, but there is no scientific evidence that EHS has non-natural origins.

Causes

The cause of EHS is unknown. A number of hypotheses have been put forth with the most common being dysfunction of the reticular formation in the brainstem responsible for transition between waking and sleeping.

Other theories into causes of EHS include:

• Minor seizures affecting the temporal lobe
• Ear dysfunctions, including sudden shifts in middle ear components or the Eustachian tube, or a rupture of the membranous labyrinth or labyrinthine fistula
• Stress and anxiety
• Variable and broken sleep, associated with a decline in delta sleep
• Antidepressant discontinuation syndrome
• Temporary calcium channel dysfunction.
• PTSD

Diagnosis

Classification

Exploding head syndrome is classified under other parasomnias by the 2014 International Classification of Sleep Disorders (ICSD, 3rd.Ed.) and is an unusual type of auditory hallucination in that it occurs in people who are not fully awake.

According to ICD-10 and DSM-5 EHS is classified as either another specified sleep-wake disorder (codes:780.59 or G47.8) or unspecified sleep-wake disorder (codes: 780.59 or G47.9).

Treatment

As of 2018, no clinical trials had been conducted to determine what treatments are safe and effective; a few case reports had been published describing treatment of small numbers of people (two to twelve per report) with clomipramine, flunarizine, nifedipine, topiramate, carbamazepine. Studies suggest that education and reassurance can reduce the frequency of EHS episodes. There is some evidence that individuals with EHS rarely report episodes to medical professionals.

Epidemiology

There have not been sufficient studies to make conclusive statements about how common or who is most often affected. One study found that 14% of a sample of undergrads reported at least one episode over the course of their lives, with higher rates in those who also have sleep paralysis.

History

Case reports of EHS have been published since at least 1876, which Silas Weir Mitchell described as "sensory discharges" in a patient. However, it has been suggested that the earliest written account of EHS was described in the biography of the French philosopher René Descartes in 1691. The phrase "snapping of the brain" was coined in 1920 by the British physician and psychiatrist Robert Armstrong-Jones. A detailed description of the syndrome and the name "exploding head syndrome" was given by British neurologist John M. S. Pearce in 1989. More recently, Peter Goadsby and Brian Sharpless have proposed renaming EHS "episodic cranial sensory shock" as it describes the symptoms more accurately (including the non-auditory elements) and better attributes to Mitchell.

The Hum

From Wikipedia, the free encyclopedia

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

The Hum is a name often given to widespread reports of a persistent and invasive low-frequency humming, rumbling, or droning noise not audible to all people. Hums have been widely reported by national media in the UK and the United States, and sometimes named according to the locality where the problem has been particularly publicized: e.g., the "Bristol Hum", the "Taos Hum" and the "Windsor Hum."

It is unclear whether it is a single phenomenon; different causes have been attributed. In some cases, it may be a manifestation of tinnitus.

Description

The essential element that defines the Hum is what is perceived as a persistent low-frequency sound, often described as being comparable to that of a distant diesel engine idling, or to some similar low-pitched sound for which obvious sources (e.g., household appliances, traffic noise, etc.) have been ruled out. There are a number of audio reproductions of the Hum available on the web, as well as at least one purported recording.

Other elements seem to be significantly associated with the Hum, being reported by an important proportion of hearers, but not by all of them. Some people hear the Hum only, or much more, inside buildings as compared with outdoors. Some perceive vibrations that can be felt through the body. Earplugs are reported as not decreasing it.

A study into the Taos Hum indicated that at least two percent could hear it; each hearer at a different frequency between 32 Hz and 80 Hz, modulated from 0.5 to 2 Hz. Similar results have been found in an earlier British study. It seems to be possible for hearers to move away from it, with one hearer of the Taos Hum reporting its range was 30 miles (48 km). There are approximately equal percentages of male and female hearers. Age does appear to be a factor, with middle aged people being more likely to hear it.

In 2006, Tom Moir, then of Massey University in Auckland, New Zealand, believes he has made several recordings of the Auckland Hum. His previous research using simulated sounds had indicated that the hum was around 56 hertz.

There is skepticism as to whether it exists as a physical sound. In 2009, the head of audiology at Addenbrooke's Hospital in Cambridge, David Baguley, said he believed people's problems with the hum were based on the physical world about one-third of the time, and stemmed from people focusing too keenly on innocuous background sounds the other two-thirds of the time. His current research focuses on using psychology and relaxation techniques to minimise distress, which can lead to a quieting or even removal of the noise.

Geoff Leventhall, a noise and vibration expert, has suggested cognitive behavioral therapy may be effective in helping those affected. "It's a question of whether you tense up to the noise or are relaxed about it. The CBT was shown to work, by helping people to take a different attitude to it."

History

There has been little mainstream attention. Only a handful of articles have been published in scientific literature, including: Leventhall, 2004, 2003; Cowan, 2003; Mullins & Kelly, 1998, 1995; Broner, 1978; Vasudevan & Gordon, 1977. Other publications include: Fox, 1989; Wilson, 1979; Hanlon, 1973.

The Hum has been reported worldwide.

Possible explanations

Mechanical devices

Although an obvious candidate, given the common description of the hum as sounding like a diesel engine, the majority of reported hums have not been traced to a specific mechanical source.

In the case of Kokomo, Indiana, a city with heavy industry, the origin of the hum was thought to have been traced to two sources. The first was a 36-hertz tone from a cooling tower at the local DaimlerChrysler casting plant and the second was a 10-hertz tone from an air compressor intake at the Haynes International plant. After those devices were corrected, however, reports of the hum persisted.

Two hums have been linked to mechanical sources. The West Seattle Hum was traced to a vacuum pump used by CalPortland to offload cargo from ships. After CalPortland replaced the silencers on the machine, reports of the hum ceased. Likewise, the Wellington Hum is thought to have been due to the diesel generator on a visiting ship. A 35 Hz hum in Windsor, Ontario, is likely to have originated from a steelworks on the industrial zone of Zug Island near Detroit.

One hum in Myrtle Beach, South Carolina was suspected of originating at a Santee Cooper substation almost 2 miles away from the home of a couple who first reported it. The substation is home to the largest transformer in the state. One local couple sued the power company for the disruption the hum was causing them. The hum was louder inside their house than out, in part, they believed, because their house vibrated in resonance to the 60 Hz hum. The volume of the hum was measured at up to 64.1 dB in the couple's home.

Some sources claim that very low frequency radio waves or extremely low frequency radio waves that are used to communicate with submarines might be the source for the hum.

Tinnitus

A suggested diagnosis of tinnitus, a self-reported disturbance of the auditory system, is used by some physicians in response to complaints about the Hum. Tinnitus is generated internally by the auditory and nervous systems, with no external stimulus.

While the Hum is hypothesized by some to be a form of low frequency tinnitus such as the venous hum, some report it is not internal, being worse inside their homes than outside. However, others insist that it is equally bad indoors and outdoors. Some people notice the Hum only at home, while others hear it everywhere they go. Some sufferers report that it is made worse by soundproofing (e.g., double glazing), which serves only to decrease other environmental noise, thus making the Hum more apparent.

Tinnitus is known to be exacerbated by allergens, which are regional and seasonal. Due to blockages, inflammation, and pressure inside the head, taking allergy medicine may help to mitigate the Hum.

Spontaneous otoacoustic emissions

Human ears generate their own noises, called spontaneous otoacoustic emissions (SOAE). Various studies have shown that 38–60% of adults with normal hearing have them, although the majority are unaware of these sounds. The people who do hear these sounds typically hear a faint hissing (cicada insect like sound), buzzing or ringing, especially if they are otherwise in complete silence.

Researchers who looked at the Taos Hum considered otoacoustic emissions as a possibility.

Animals

One of the many possible causes of the West Seattle Hum considered was that it was related to the midshipman fish, also known as a toadfish. A previous hum in Sausalito, California, also on the west coast of the United States, was determined to be the mating call of the male midshipman. However, in that case the hum was resonating through houseboat hulls and affecting the people living on those boats. In the West Seattle case, the University of Washington researcher determined that it would be impossible for any resonating hum, transmitted via tanker or boat hulls, to be transmitted very far inland; certainly not far enough to account for the reports.

The Scottish Association for Marine Science hypothesised that the nocturnal humming sound heard in Hythe, Hampshire in the UK could be produced by a similar "sonic" fish. The council believed this to be unlikely because such fish are not commonly found in inshore waters of the UK. As of February 2014, the source had not been located, although the sound has now been recorded.

A case of "hum" in a house, reported in the Daily Telegraph's 'Letters from Readers' on 18 January 2018, proved to be a wasps' nest in a hollow wall.

Media coverage

The Taos Hum was featured on the TV show Unsolved Mysteries. It was also featured in LiveScience's "Top Ten Unexplained Phenomena", where it took tenth place.

BBC Radio 4 in the UK featured an investigation of the Hum phenomena in their Punt PI fact-based comedy programme.

In popular culture

• In a 1998 episode of The X-Files titled "Drive", Agent Mulder speculates that extremely low frequency (ELF) radio waves "may be behind the so-called Taos Hum".
• In the 2002 episode of Monk titled “Mr. Monk and the Billionaire Mugger”, the Hum can be heard multiple times while the engine is repaired on Sharona’s car.
• In the 2011 episode of Murdoch Mysteries titled “Tattered and Torn”, the Hum can be heard while Murdoch interviews Malcolm Lamb.
• In a 2018 episode of Criminal Minds titled "Mixed Signals", the unknown subject's wife was driven to suicide by the Hum, which sparked his killing spree.
• In a 2019 episode of The UnXplained titled "Unnatural Nature", documenting the hum.