Sleep is a natural state of bodily rest observed throughout the animal kingdom. It is common to all mammals and birds, and is also seen in many reptiles, amphibians and fish. Mammals ( class Mammalia) are a class of Vertebrate Animals characterized by the presence of Sweat glands, including sweat glands Birds ( class Aves) are bipedal endothermic ( Warm-blooded) Vertebrate animals that lay eggs. Reptiles, or members of the class Reptilia are air-breathing Cold-blooded Vertebrates that have skin covered in scales as opposed to hair or feathers Prehistoric amphibian Amphibians (class Amphibia such as Frogs Toads Salamanders Newts Gymnophiona, Sirens and Fish are aquatic Vertebrate animals that are typically ectothermic (previously Cold-blooded) covered with scales, and equipped with two

In humans, other mammals, and a substantial majority of other animals which have been studied — such as fish, birds, ants, and fruit-flies — regular sleep is essential for survival. Ants are social Insects of the family Formicidae and along with the related families of Wasps and Bees belong to the order Drosophilidae is a diverse cosmopolitan family of flies, including the Genus Drosophila, which includes fruit flies However its purposes are only partly clear and are the subject of intense research. ^[1]

Contents 1 Physiology 1.1 Stages of sleep 1.2 Sleep timing 1.3 Optimal amount in humans 1.3.1 Adults 1.3.2 Hours by age 1.4 Sleep debt 2 Functions 2.1 Restoration 2.2 Anabolic/catabolic 2.3 Ontogenesis 2.4 Memory processing 2.5 Preservation 3 Dreaming 4 Effect of food and drink on sleep 4.1 Drowsiness 4.2 Stimulation 5 Causes of difficulty in sleeping 6 Anthropology of sleep 7 Sleep in non-humans 8 Longest period without sleep 9 See also 9.1 Common sleeping positions, practices, and rituals 9.2 Other 10 References 11 Further reading 12 External links

Physiology

In mammals and birds the measurement of eye movement during sleep is used to divide sleep into two broad types:

• rapid eye movement (REM) and
• non-rapid eye movement (NREM) sleep. The Sleep stages 1 through 4 are collectively referred to as NREM (non-rapid eye movement sleep

Each type has a distinct set of associated physiological, neurological and psychological features.

Sleep proceeds in cycles of REM and the four stages of NREM, the order normally being:

stages 1 > 2 > 3 > 4 > 3 > 2 > REM.

In humans this cycle is on average 90 to 110 minutes,^[2] with a greater amount of stages 3 and 4 early in the night and more REM later in the night. Each phase may have a distinct physiological function.

Drugs such as sleeping pills and alcoholic beverages can suppress certain stages of sleep (see Sleep deprivation). A sedative, or more specifically a sedative-hypnotic, is a substance that depresses the Central nervous system (CNS resulting in calmness relaxation sleepiness Sleep deprivation is a general lack of the necessary amount of Sleep. This can result in a sleep that exhibits loss of consciousness but does not fulfill its physiological functions.

Rechtschaffen and Kales originally outlined the criteria for staging sleep in 1968. The American Academy of Sleep Medicine (AASM) updated the staging rules in 2007.

Stages of sleep

Criteria for REM sleep include not only rapid eye movements but also a rapid low voltage EEG. In mammals, at least, low muscle tone is also seen. Most memorable dreaming occurs in this stage.

NREM accounts for 75–80% of total sleep time in normal human adults. In NREM sleep, there is relatively little dreaming. Non-REM encompasses four stages; stages 1 and 2 are considered 'light sleep', and 3 and 4 'deep sleep' or slow-wave sleep, SWS. Slow-wave sleep (SWS is stages three and four of Non-rapid eye movement sleep. They are differentiated solely using EEG, unlike REM sleep which is characterized by rapid eye movements and relative absence of muscle tone. In non-REM sleep there are often limb movements, and parasomnias such as sleepwalking may occur. Parasomnias are a wide variety of disorders that revolve around sleep Sleepwalking (also called somnambulism or noctambulism) is a Parasomnia or Sleep disorder where the sufferer engages in

A cyclical alternating pattern may sometimes be observed during a stage. Irrevlevant article Cyclical Alternating Pattern occurs in Sleep.

NREM consists of four stages according to the 2007 AASM standards:

• During Stage N1 the brain transitions from alpha waves (common to people who are awake and having a frequency of 8 to 13 Hz) to theta waves (frequency of 4 to 7 Hz). Alpha waves are Electromagnetic oscillations in the frequency range of 8–12 Hz arising from synchronous and coherent ( in phase The hertz (symbol Hz) is a measure of Frequency, informally defined as the number of events occurring per Second. Theta rhythms are one of several characteristic electroencephalogram (EEG waveforms associated with various Sleep and wakefulness states of the Brain This stage is sometimes referred to as somnolence, or "drowsy sleep". Associated with the onset of sleep during N1 may be sudden twitches and hypnic jerks. A hypnic or hypnagogic jerk is an involuntary muscle twitch (commonly known as a myoclonic twitch) which occurs during Hypnagogia. Some people may also experience hypnagogic hallucinations during this stage, which can be more troublesome to the subject. Hypnagogia ( Greek ὕπνος húpnos "sleep" + the root found in ἄγω ágō "to lead away conduct convey" ἀγωγεύς During N1 the subject loses some muscle tone, and conscious awareness of the external environment. In Physiology, Medicine, and Anatomy, muscle tone (aka residual muscle tension or tonus) is the continuous and passive partial
• Stage N2, is characterized by "sleep spindles" (12 to 16 Hz) and "K-complexes. A sleep spindle is burst of brain activity visible on an EEG that occurs during stage 2 sleep. A K-complex is an EEG waveform that occurs during stage 2 sleep. " During this stage, muscular activity as measured by electromyography (EMG) lowers and conscious awareness of the external environment disappears. Electromyography (EMG is a technique for evaluating and recording the activation signal of muscles This stage occupies 45 to 55% of total sleep.
• In Stage N3, the delta waves, also called delta rhythms (0. A delta wave is a high Amplitude Brain wave with a frequency of 1-4 Hertz which can be recorded with an electroencephalogram (EEG and 5 to 4 Hz) make up less than 50% of the total wave-patterns. This is considered part of deep or slow-wave sleep (SWS) and appears to function primarily as a transition into stage N4. This is the stage in which night terrors, bedwetting, sleepwalking and sleep-talking occur. A night terror, also known as pavor nocturnus, is a Parasomnia disorder characterized by extreme terror and a temporary inability to regain full consciousness Bedwetting is involuntary Urination while asleep after the age at which bladder control would normally be anticipated Sleepwalking (also called somnambulism or noctambulism) is a Parasomnia or Sleep disorder where the sufferer engages in Somniloquy or sleep-talking is a Parasomnia that refers to talking aloud in one's sleep
• In Stage N4, delta-waves make up more than 50% of the wave-patterns. Stages N3 and N4 are the deepest forms of sleep; N4 is effectively a deeper version of N3, in which the deep-sleep characteristics, such as delta-waves, are more pronounced. ^[3]

Both REM sleep and NREM sleep stages 3 and 4 are homeostatically driven; that is, if a person or animal is selectively deprived of one of these, it rebounds once uninhibited sleep again is allowed. This suggests that both are essential to the functions of the sleep process.

Sleep timing

Sleep timing is controlled by the circadian clock, by homeostasis and, in humans, by willed behavior. Homeostasis (from Greek: ὅμος hómos, "equal" and ιστημι istēmi, "to stand" lit

The circadian clock, an inner time-keeping, temperature-fluctuating, enzyme-controlling device, works in tandem with adenosine, a neurotransmitter which inhibits many of the bodily processes that are associated with wakefulness. Adenosine is a Nucleoside composed of a Molecule of Adenine attached to a Ribose sugar molecule ( Ribofuranose) moiety via a β-N9- Adenosine is created over the course of the day; high levels of adenosine lead to sleepiness. In diurnal animals, sleepiness occurs as the circadian element causes the release of the hormone melatonin and a gradual decrease in core body temperature. Melatonin is a naturally occurring Hormone found in most animals including humans and some other living organisms including Algae. The timing is affected by one's chronotype. Not to be confused with Bakhtin's Chronotope. Chronotype is an attribute of human beings reflecting whether they are alert and prefer to be active It is the circadian rhythm which determines the ideal timing of a correctly structured and restorative sleep episode. ^[4]

Homeostatic sleep propensity, the need for sleep as a function of the amount of time elapsed since the last adequate sleep episode, is also important and must be balanced against the circadian element for satisfactory sleep. Along with corresponding messages from the circadian clock, this tells the body it needs to sleep. ^[5]

Sleep offset, awakening, is primarily determined by circadian rhythm. A normal person who regularly awakens at an early hour will generally not be able to sleep much later than the person's normal waking time, even if moderately sleep deprived.

Optimal amount in humans

Adults

The optimal amount of sleep is not a meaningful concept unless the timing of that sleep is seen in relation to an individual's circadian rhythms. A person's major sleep episode is relatively inefficient and inadequate when it occurs at the "wrong" time of day. The timing is correct when the following two circadian markers occur after the middle of the sleep episode but before awakening:^[6]

• maximum concentration of the hormone melatonin, and
• minimum core body temperature.

The National Sleep Foundation in the United States maintains that eight to nine hours of sleep for adult humans is optimal and that sufficient sleep benefits alertness, memory and problem solving, and overall health, as well as reducing the risk of accidents. The National Sleep Foundation (NSF is an independent nonprofit organization dedicated to improving public health and safety by achieving understanding of Sleep and Sleep disorders ^[7] A widely publicized 2003 study^[8] performed at the University of Pennsylvania School of Medicine demonstrated that cognitive performance declines with fewer than eight hours of sleep. The University of Pennsylvania 's School of Medicine, presently located in the University City section of Philadelphia, Pennsylvania, was

However, a University of California, San Diego psychiatry study of more than one million adults found that people who live the longest self-report sleeping for six to seven hours each night. The University of California San Diego (popularly known as UC San Diego or UCSD) is a public Research university in San Diego, California ^[9] Another study of sleep duration and mortality risk in women showed similar results. ^[10] Other studies show that "sleeping more than 7 to 8 hours per day has been consistently associated with increased mortality"^[11]

Causal links are currently speculative: the available data may only reflect comorbid depression, socioeconomic status, or even alcohol use, for example. ^[12] These studies cannot be used to determine optimal sleep habits, only correlation — and empirically observed correlation is a necessary but not sufficient condition for causality. Correlation does not imply causation is a phrase used in the Sciences and Statistics to emphasize that Correlation between two variables does not imply A need for nine or ten hours of sleep a day, or only five to six, may or may not have the same cause as the shortened life span. In other words, long or short sleep duration itself has not been shown to be a cause of early death.

Researchers from the University of Warwick and University College London have found that lack of sleep can more than double the risk of death from cardiovascular disease, but that too much sleep can also double the risk of death. The University of Warwick is a British Campus university located on the outskirts of Coventry, West Midlands, England and is University College London ( UCL) is a multi-faculty university institution based in the United Kingdom and a constituent college of the University of London Cardiovascular disease or cardiovascular diseases refers to the class of diseases that involve the Heart or Blood vessels ( arteries and ^[13][14] Professor Francesco Cappuccio said: “Short sleep has been shown to be a risk factor for weight gain, hypertension and Type 2 diabetes sometimes leading to mortality but in contrast to the short sleep-mortality association it appears that no potential mechanisms by which long sleep could be associated with increased mortality have yet been investigated. Hypertension, also referred to as high blood pressure, HTN or HPN, is a medical condition in which the Blood pressure is chronically elevated Some candidate causes for this include depression, low socioeconomic status and cancer-related fatigue. [. . . ] In terms of prevention, our findings indicate that consistently sleeping around 7 hours per night is optimal for health and a sustained reduction may predispose to ill-health. ”

Hours by age

Children need a greater amount of sleep per day than adults to develop and function properly: up to 18 hours for newborn babies, with a declining rate as a child ages. ^[7][15] A newborn baby spends almost half of its sleep time in REM-sleep. By the age of five or so, only a bit over two hours are spent in REM. ^[16]

Age	Average amount of sleep per day
Newborn	up to 18 hours
1-12 months	14–18 hours
1-3 years	12-15 hours
3-5 years	11-13 hours
5-12 years	9-11 hours
Adolescents	9-10 hours
Adults, including elderly	7-8 (+) hours
Pregnant women	8 (+) hours

Sleep debt

Main article: Sleep debt

Sleep debt is the effect of not getting enough rest and sleep; a large debt causes mental and physical fatigue. Sleep debt is the cumulative effect of not getting enough Sleep. Scientists do not agree on how much sleep debt it is possible to accumulate, nor on whether the prevalence of sleep debt among adults has changed appreciably in the industrialized world in recent decades. It is likely that children are sleeping less than previously in Western societies. ^[17]

Functions

The multiple theories proposed to explain the function of sleep are reflective of the as yet incomplete understanding of the subject.

It is likely that sleep evolved to fulfill some primeval function, but has taken over multiple functions over time as organisms have evolved. An analogy would be that of the larynx, which performs multiple functions such as controlling the passage of food and air, phonation for communicating and social purposes, etc. These are all functions of the larynx but just one of them likely represents the original function. Some of the many proposed functions of sleep are as follows:

Restoration

Wound healing has been shown to be affected by sleep. Wound healing, or wound repair, is the body's natural process of regenerating dermal and epidermal tissue. A study conducted by Gumustekin et al. ^[18] in 2004 shows sleep deprivation hindering the healing of burns on rats. Healing, assessed physically is the process by which the cells in the Body regenerate and repair to reduce the size of a damaged or necrotic area

It has also been shown that sleep deprivation affects the immune system and metabolism. An immune system is a collection of mechanisms within an Organism that protects against Disease by identifying and killing Pathogens and Tumor Metabolism is the set of Chemical reactions that occur in living Organisms in order to maintain Life. In a study by Zager et al in 2007,^[19] rats were deprived of sleep for 24 hours. When compared with a control group, the sleep-deprived rats' blood tests indicated a 20% decrease in white blood cell count, a significant change in the immune system.

A study by Bonnet and Arand^[20] in 2003 indicates that sleep affects metabolism. Comparing normal human sleepers and sleepers with sleep state misperception insomnia, where patients complain of poor sleep but have normal sleep by electroencephalographic (EEG) criteria, the researchers found significantly greater metabolism values for the normal sleepers.

It has yet to be clearly proven that sleep duration affects somatic growth. "Somatic" redirects here for the musician known as Somatic see Hahn Rowe. One study by Jenni et al^[21] in 2007 recorded growth, height and weight, as correlated to parent-reported time-in-bed in 305 children over a period of nine years (age 1-10). It was found that "the variation of sleep duration among children does not seem to have an effect on growth". It has been shown that sleep, more specifically slow-wave sleep (SWS), does affect growth hormone levels in adult men. Growth hormone ( GH) is a Peptide hormone that stimulates growth and cell reproduction in humans and other animals During eight hours sleep, Van Cauter, Leproult, and Plat^[22] found that the men with a high percentage of SWS (average 24%) also had high growth hormone secretion, while subjects with a low percentage of SWS (average 9%) had low growth hormone secretion.

There are multiple arguments supporting the restorative function of sleep. We feel rested after sleeping, and it is natural to assume that this is a basic purpose of sleep. Overall metabolic rate goes down during sleep and certain anabolic hormones such as growth hormones as mentioned above are secreted preferentially during sleep. Sleep among species is, in general, inversely related to the animal size and basal metabolic rate. Basal metabolic rate ( BMR) is the amount of energy expended while at rest in a neutrally temperate environment in the post-absorptive state (meaning that the digestive system Rats with a very high basal metabolic rate sleep for up to 14 hours a day whereas elephants and giraffes with lower BMRs sleep only 3-4 hours per day.

Energy conservation could as well have been accomplished by resting quiescent without shutting off the organism from the environment, potentially a dangerous situation. A sedentary non-sleeping animal is more likely to survive predators, while still preserving energy. Sleep therefore does something else other than conserving energy. Most interestingly, hibernating animals, when they wake up from hibernation go into rebound sleep because of lack of sleep during the hibernation period. For the ability of certain operating systems see Hibernate (OS feature Hibernation is a state of inactivity and metabolic depression They are definitely well rested and are conserving energy during hibernation, but need sleep for something else. ^[23] One study that was conducted kept rats awake indefinitely. They started dying after 5 days.

Anabolic/catabolic

Non-REM sleep may be an anabolic state marked by physiological processes of growth and rejuvenation of the organism's immune, nervous, muscular, and skeletal systems (but see above). The Sleep stages 1 through 4 are collectively referred to as NREM (non-rapid eye movement sleep Anabolism is the set of Metabolic pathways that construct molecules from smaller units Wakefulness may perhaps be viewed as a cyclical, temporary, hyperactive catabolic state during which the organism acquires nourishment and procreates. For the related metabolic process see Anabolism. Catabolism is the set of Metabolic pathways which break down molecules into

Ontogenesis

According to the ontogenetic hypothesis of REM sleep, the activity occurring during neonatal REM sleep (or active sleep) seems to be particularly important to the developing organism (Marks et al. Ontogeny, as opposed to Phylogeny, refers to the history of an organism from birth as opposed to its genetic makeup , 1995). Studies investigating the effects of deprivation of active sleep have shown that deprivation early in life can result in behavioral problems, permanent sleep disruption, decreased brain mass (Mirmiran et al. 1983), and an abnormal amount of neuronal cell death (Morrissey, Duntley & Anch, 2004).

REM sleep appears to be important for development of the brain. REM sleep occupies majority of time of sleep of infants, which spend most of their time sleeping. Among different species, the more immature the baby is born, the more time it spends in REM sleep. Proponents also suggest that REM-induced muscle inhibition in the presence of brain activation exists to allow for brain development by activating the synapses yet without any motor consequences which may get the infant in trouble. Additionally, REM deprivation results in developmental abnormalities later in life.

However, this does not explain why older adults still need REM sleep, and why the fraction of time spent does not change significantly as one ages. Aquatic mammal infants do not have REM sleep in infancy. REM sleep in those animals increases as they age. Obviously, REM sleep is not needed for development in these animals.

Memory processing

Scientists have shown numerous ways in which sleep is related to memory. In Psychology, memory is an organism's ability to store retain and subsequently retrieve information In a study conducted by Turner, Drummond, Salamat, and Brown^[24] working memory was shown to be affected by sleep deprivation. Working memory (also referred to as Short term memory, depending on the specific theory is a theoretical construct within Cognitive psychology that refers to the Working memory is important because it keeps information active for further processing and supports higher-level cognitive functions such as decision making, reasoning, and episodic memory. In some forms of Psychological testing, particularly those related to the Myers-Briggs Type Indicator, the cognitive functions (sometimes known as mental Decision making can be regarded as an outcome of mental processes ( cognitive process) leading to the selection of a course of action among several alternatives Reasoning is the cognitive process of looking for Reasons for beliefs conclusions actions or feelings Episodic memory is the Memory of unique personal experiences ( Events Times Places associated Emotions and other conception-based Turner et al. allowed 18 women and 22 men to sleep only 26 minutes per night over a 4-day period. Subjects were given initial cognitive tests while well rested and then tested again twice a day during the 4 days of sleep deprivation. Cognitive tests are Assessments of the Cognitive capabilities of Humans and Animals Tests administered to Humans include various forms On the final test the average working memory span of the sleep deprived group had dropped by 38% in comparison to the control group.

Memory also seems to be affected differently by certain stages of sleep such as REM and slow-wave sleep (SWS). In one study cited in Born, Rasch, and Gais^[25] multiple groups of human subjects were used: wake control groups and sleep test groups. Sleep and wake groups were taught a task and then tested on it both on early and late nights, with the order of nights balanced across participants. When the subject’s brains were scanned during sleep, hypnograms revealed that SWS was the dominant sleep stage during the early night representing around 23% on average for sleep stage activity. The early night test group performed 16% better on the declarative memory test than the control group. Declarative memory is the aspect of human Memory that stores Facts It is so called because it refers to memories that can be consciously discussed or declared During late night sleep, REM became the most active sleep stage at about 24%, and the late night test group performed 25% better on the procedural memory test than the control group. Procedural memory is the long-term Memory of Skills and procedures or "how to" knowledge ( Procedural knowledge) This indicates that procedural memory benefits from late REM-rich sleep where as declarative memory benefits from early SWS-rich sleep.

Another study conducted by Datta^[26] indirectly supports these results. The subjects chosen were 22 male rats. A box was constructed where a single rat could move freely from one end to the other. The bottom of the box was made of a steel grate. A light would shine in the box accompanied by a sound. After a 5 second delay an electrical shock would be applied. Once the shock commenced the rat could move to the other end of the box, ending the shock immediately. The rat could also use the 5 second delay to move to the other end of the box and avoid the shock entirely. The length of the shock never exceeded 5 seconds. This was repeated 30 times for half the rats. The other half, the control group, was placed in the same trial but the rats were shocked regardless of their reaction. After each of the training sessions the rat would be placed in a recording cage for 6 hours of polygraphic recordings. This process was repeated for 3 consecutive days. This study found that during the post-trial sleep recording session rats spent 25. 47% more time in REM sleep after learning trials than after control trials. These trials support the results of the Born et al. study, indicating an obvious correlation between REM sleep and procedural knowledge. Procedural knowledge is the knowledge exercised in the performance of some task

Another interesting observation of the Datta study is that the learning group spent 180% more time in SWS than did the control group during the post-trial sleep-recording session. This phenomenon is supported by a study performed by Kudrimoti, Barnes, and McNaughton. ^[27] This study shows that after spatial exploration activity, patterns of hippocampal place cells are reactivated during SWS following the experiment. In a study by Kudrimoti et al seven rats were run through a linear track using rewards on either end. The rats would then be placed in the track for 30 minutes to allow them to adjust (PRE), then they ran the track with reward based training for 30 minutes (RUN), and then they were allowed to rest for 30 minutes. During each of these three periods EEG data was collected for information on the rats’ sleep stages. Kudrimoti et al computed the mean firing rates of hippocampal place cells during pre-behavior SWS (PRE) and three 10 min intervals in post-behavior SWS (POST) by averaging across 22 track-running sessions from seven rats. The results showed that 10 min after the trial RUN session there was a 12% increase in the mean firing rate of hippocampal place cells from the PRE level, however after 20 minutes the mean firing rate returned rapidly toward the PRE level. The elevated firing of hippocampal place cells during SWS after spatial exploration could explain why there were elevated levels of SWS sleep in Datta’s study as it also dealt with a form of spatial exploration.

The different studies all suggest that there is a correlation between sleep and the many complex functions of memory.

Further information: Sleep and learning, Sleep and creativity

Preservation

The "Preservation and Protection" theory holds that sleep serves an adaptive function. Many competing theories have been advanced to discover the possible connections between sleep and learning in Humans. The majority of studies on Sleep and Creativity have shown that sleep can facilitate insightful behavior and flexible reasoning It protects the person during that portion of the 24-hour day in which being awake, and hence roaming around, would place the individual at greatest risk. Organisms do not require 24 hours to feed themselves and meet other necessities. From this perspective of adaptation, organisms are safer by staying out of harm's way where potentially they could be prey to other, stronger organisms. They sleep at times that maximize their safety, given their physical capacities and their habitats. (Allison & Cicchetti, 1976; Webb, 1982).

However, this theory fails to explain why the brain disengages from the external environment during normal sleep. Another argument against the theory is that sleep is not simply a passive consequence of removing the animal from the environment, but is a "drive": animals alter their behaviors in order to obtain sleep. Therefore, circadian regulation is more than sufficient to explain periods of activity and quiescence that are adaptive to an organism, but the more peculiar specializations of sleep probably serve different and unknown functions.

Moreover, the preservation theory does not explain why carnivores like lions, which are on top of the food chain, sleep the most. By the preservation logic, these top carnivores should not need any sleep at all. Preservation does not explain why aquatic mammals sleep while moving. Lethargy during these vulnerable hours would do the same, and will be more advantageous because the animal will be quiescent but still be able to respond to environmental challenges like predators etc. Sleep rebound that occurs after a sleepless night will be maladaptive, but still occurs for a reason. For example, a zebra falling asleep the day after it spent the sleeping time running from a lion is more and not less vulnerable to predation.

Dreaming

Main article: Dream

Dreaming is the perception of sensory images during sleep, in a sequence which the sleeper/dreamer usually perceives more as an apparent participant than an observer. Dreams are the images sounds thoughts and feelings experienced while Sleeping, particularly strongly associated with Rapid eye movement sleep. Dreaming is stimulated by the pons and mostly occurs during the REM phase of sleep. The pons (sometimes pons Varolii after Costanzo Varolio) is a structure located on the Brain stem.

People have proposed many hypotheses about the functions of dreaming. A hypothesis (from Greek) consists either of a suggested explanation for a phenomenon (an event that is observable or of a reasoned proposal suggesting a possible Sigmund Freud postulated that dreams are the symbolic expression of frustrated desires that had been relegated to the subconscious, and he used dream interpretation in the form of psychoanalysis to uncover these desires. Sigmund Freud (ˈziːkmʊnt ˈfʁɔʏt born Sigismund Shlomo Freud (May 6 1856 &ndash September 23 1939 was an Austrian Psychiatrist who founded The term subconscious is defined as existing or operating in the Mind beneath or beyond Conscious Awareness. For the John Cale minimalist album see Dream Interpretation (Album Dream interpretation is the process of assigning meaning to Dreams In many of the Psychoanalysis is a body of ideas developed by Austrian physician Sigmund Freud and his followers which is devoted to the study of human psychological functioning and behavior Scientists have become skeptical about the Freudian interpretation, and place more emphasis on dreaming as a requirement for organization and consolidation of recent memory and experience. In Psychology, memory is an organism's ability to store retain and subsequently retrieve information See Freud:The Interpretation of Dreams

Rosalind Cartwright stated that "One Function of dreams may be to restore our sense of competence. The Interpretation of Dreams is a book by Sigmund Freud. The first edition was first published in German in November 1899 as Die Traumdeutung . . it is also probable that in many times of stress, dreams have more work to do in resolving our problems and are thus more salient and memorable. "

J. Allan Hobson's and Robert McCarley's activation synthesis theory proposes that dreams are caused by the random firing of neurons in the cerebral cortex during the REM period. John Allan Hobson, MD (born June 3, 1933) is an American Psychiatrist and Dream researcher Robert W McCarley, MD is Chair and Professor of Psychiatry at Harvard Medical School and the VA Boston Healthcare System. Activation Synthesis Theory is a neurobiological theory of Dreams, put forward by James Allan Hobson and Robert McCarley in 1977, Randomness is a lack of order Purpose, cause, or predictability Neurons (ˈnjuːɹɒn also known as neurones and nerve cells) are responsive cells in the Nervous system that process and transmit information The cerebral cortex is a structure within the Brain that plays a key role in Memory, Attention, perceptual Awareness, Thought, According to the theory, the forebrain then creates a story in an attempt to reconcile and make sense of the nonsensical sensory information presented to it, hence the odd nature of many dreams. In the Anatomy of the Brain of Vertebrates, the prosencephalon (or forebrain) is the Rostral -most (forward-most portion of the ^[28]

Effect of food and drink on sleep

Drowsiness

• Tryptophan

The amino acid tryptophan is a building block of the protein found in foods. Tryptophan (abbreviated as Trp or W) is one of the 20 standard amino acids, as well as an Essential amino acid in the Human diet It contributes to sleepiness. Carbohydrates make tryptophan more available to the brain, which is why carbohydrate-heavy meals containing tryptophan tend to cause drowsiness.

• Melatonin

Melatonin is a naturally occurring hormone that regulates sleepiness. It is made in the brain where tryptophan is converted into serotonin and then into melatonin, which is released at night by the pineal gland to induce and maintain sleep. The pineal gland (also called the pineal body, epiphysis cerebri, or epiphysis) is a small endocrine gland in the vertebrate Brain Melatonin supplementation may be used as a sleep aid, both as a hypnotic and as a chronobiotic (see phase response curve, PRC). For the state of mind see Hypnosis. Hypnotic drugs induce Sleep (which differentiates them from the Sedative A phase response curve (PRC illustrates the relationship between the timing and the effect of a treatment designed to affect Circadian rhythms Normally the various rhythms

• The "Post-Lunch Dip"

Many people have a temporary drop in alertness in early afternoon, commonly known as the post-lunch dip. While a large meal, rich in carbohydrates, can make a person feel sleepy, the post-lunch dip is mostly an effect of the biological clock. People naturally feel most sleepy (have the greatest "drive for sleep") at two times of the day about 12 hours apart, for example at 2:00 AM and 2:00 PM. At those two times, the body clock "kicks in". At about 2 p. m. (14:00), it overrides the homeostatic build-up of sleep debt, allowing several more hours of wakefulness. At about 2 a. m. (02:00), with the daily sleep debt paid off, it "kicks in" again to ensure a few more hours of sleep.

• Alcohol

Alcoholic beverages aid relaxation and commonly are used as a sleep aid. Alcohol tends, however, to disrupt sleep throughout the night and can prevent the deeper stages of sleep from occurring.

Stimulation

• Caffeine

Caffeine is a stimulant that works by slowing the action of the hormones in the brain that cause sleepiness. Caffeine is a bitter white crystalline Xanthine Alkaloid that acts as a Psychoactive Stimulant Drug and a mild Diuretic Effective dosage is individual, in part dependent on prior usage. It can cause a rapid reduction in alertness as it wears off.

• Amphetamines

Amphetamines are often used to treat narcolepsy, the most common effects are decreased appetite, decreased stamina, and physical energy. Amphetamine, and related drugs such as Methamphetamine are a group of drugs that act by increasing levels of Norepinephrine, Serotonin, and Dopamine Narcolepsy is a Neurological condition most characterized by Excessive Daytime Sleepiness (EDS in which a person falls asleep during the day at inappropriate

• Energy Drinks

The stimulating effects of energy drinks comes from natural stimulants such as caffeine, sugars, and essential amino acids, and eventually will create a rapid reduction in alertness similar to that of caffeine. Energy drinks are Soft drinks advertised as providing more Energy than a typical drink

Further reading: National Sleep Foundation - Topics: A to Zzzzs

Causes of difficulty in sleeping

There are a great many possible reasons for sleeping poorly. Following sleep hygienic principles may solve problems of physical or emotional discomfort. Sleep hygiene can be defined as "all behavioural and environmental factors that precede sleep and may interfere with sleep ^[29] When pain, illness, drugs or stress are the culprit, the cause must be treated. Sleep disorders, including the sleep apneas, narcolepsy, primary insomnia, periodic limb movement disorder (PLMD), restless leg syndrome (RLS) and the circadian rhythm sleep disorders, are treatable. A sleep disorder (somnipathy is a medical disorder of the Sleep patterns of a person or animal Sleep apnea is a sleep disorder characterized by pauses in Breathing during Sleep. Narcolepsy is a Neurological condition most characterized by Excessive Daytime Sleepiness (EDS in which a person falls asleep during the day at inappropriate Nocturnal myoclonus, also called Periodic Limb Movement Disorder (PLMD is a Sleep disorder where the patient moves limbs involuntarily during sleep and has symptoms Restless legs syndrome (RLS Wittmaack-Ekbom's syndrome, or sometimes but inaccurately referred to as Nocturnal myoclonus) is a condition that is characterized Circadian rhythm sleep disorders are a family of Sleep disorders affecting among other things the timing of sleep

Elderly people may to some degree lose the ability to consolidate sleep. They need the same amount per day as they've always needed, but may need to take some of their sleep as daytime naps.

Anthropology of sleep

Recent research suggests that sleep patterns vary significantly across human cultures. Culture (from the Latin cultura stemming from colere, meaning "to cultivate" generally refers to patterns of human activity and the symbolic ^[30][31] The most striking differences are between societies that have plentiful artificial light and ones that do not. Lighting includes both artificial Light sources such as lamps and natural illumination of interiors from Daylight. Cultures without artificial light have more broken-up sleep patterns. This is called polyphasic sleep or segmented sleep and has led to expressions such as "first sleep," "watch," and "second sleep" which appear in literature from all over the world. Polyphasic sleep, a term coined by early 20th century psychologist J Segmented sleep, divided sleep, bimodal sleep pattern and interrupted sleep are modern Western terms for a polyphasic or biphasic sleep pattern

Some cultures have fragmented sleep patterns in which people sleep at all times of the day, and for shorter periods at night. For example, many Mediterranean and Latin American cultures have a siesta, in which people sleep for a period in the afternoon. A siesta ( is a short nap taken in the early afternoon often after the midday Meal. Afternoon is the time of day from 1200 ( Noon) to -depending upon context- Evening, Sunset, or 1800 In many nomadic or hunter-gatherer societies people sleep off and on throughout the day or night depending on what is happening. Nomadic people, (from the νομάδες nomádes, "those who let pasture herds" also known as nomads, are communities of people that A hunter-gatherer society is one whose primary subsistence method involves the direct procurement of edible plants and animals from the wild Foraging and Hunting

Sleep in non-humans

Main article: Sleep (non-human)

Horses and other herbivorous ungulates can sleep while standing, but must necessarily lie down for REM sleep (which causes muscular atony) for short periods - giraffes, for example, only need to lie down for REM sleep for a few minutes at a time. Sleep in non-human creatures refers to how the behavioral and physiological state of Sleep, mainly characterized by reversible unconsciousness non-responsiveness to external Bats sleep while hanging upside down. Some aquatic mammals and some birds can sleep with one half of the brain, while the other half is awake, so called unihemispheric slow-wave sleep. Unihemispheric slow-wave sleep ( USWS) is Sleep in which one half of an animal's brain is at rest while the other half remains alert ^[32] Birds and mammals have cycles of non-REM and REM sleep as described above for humans, though birds’ cycles are much shorter and they do not lose muscle tone (go limp) to the same extent that most mammals do.

Many animals sleep, but neurological sleep states are difficult to define in lower order animals. In these animals, sleep is defined using behavioral characteristics such as minimal movement, postures typical for the species and reduced responsiveness to external stimulation. It is quickly reversible, as opposed to hibernation or coma, and sleep deprivation is followed by longer and/or deeper sleep. In Medicine, a coma (from the Greek koma, meaning deep sleep is a profound state of Unconsciousness.

Many species of mammals sleep for a large proportion of each 24-hour period when they are very young. ^[33] However, killer whales and some dolphins do not sleep during the first month after they are born. The Orca or Killer Whale ( Orcinus orca) less commonly Blackfish or Seawolf, is the largest species of the Oceanic dolphin family Dolphins are Marine mammals that are closely related to Whales and Porpoises There are almost forty species of dolphin in seventeen genera. ^[34]

Longest period without sleep

Depending on how sleep is defined, there are several people who can claim the record for having gone the longest without sleep:

1. Thai Ngoc, born 1942, claimed in 2006 to have been awake for 33 years or 11,700 nights, according to Vietnamese news organization Thanh Nien. Thai Ngoc or RAJPAR (born 1942 In October 2006 however Ngoc reported that he was beginning to feel "like a plant without water" due to the lack of sleep Vietnam (ˌviːɛtˈnɑːm Việt Nam) officially It was said that Ngoc acquired the ability to go without sleep after a bout of fever in 1973,^[35] but other reports indicate he stopped sleeping in 1976 with no known trigger. ^[36] At the time of the Thanh Nien report, Ngoc suffered from no apparent ill effect (other than a minor decline in liver function), was mentally sound and could carry 100 kg of pig feed down a 4 km road,^[35] but another report indicates that he was healthy before the sleepless episode but that now he was not feeling well because of the lack of sleep. ^[36]
2. In January 2005, the RIA Novosti published an article about Fyodor Nesterchuk from the Ukrainian town of Kamen-Kashirsky who claimed to have not slept in more than 20 years. RIA (Russian Information Agency Novosti is a Russian Press agency based in Moscow. Ukraine (Україна Ukrayina, /ukrɑˈjinɑ/ is a country in Eastern Europe. Local doctor Fyodor Koshel, chief of the Lutsk city health department, claimed to have examined him extensively and failed to make him sleep. Lutsk (Луцьк translit Luts’k, Łuck is a city located by the Styr River in north-western Ukraine. Koshel also said however that Nesterchuck did not suffer any of the normally deleterious effects of sleep deprivation. ^[37] Several bloggers have commented that people who claim not to sleep are usually shown to sleep when studied in sleep laboratories with EEG. ^[38] Another blog stated that Ananova's reprinting of the story is indicative of their having a reputation for not being a credible source of news. Ananova is a Web-oriented news service that originally featured a computer-simulated animation of a woman newscaster an Embodied agent named "Ananova" ^[39] The "problem" may lie in that Nesterchuck and people like him don't remember sleeping, which may be cause for further study. Whether he doesn't sleep or doesn't remember sleeping, either event indicates a condition not present in most humans. Nesterchuck reports experiencing drowsiness at night, commenting that he attempts to sleep "in vain" when he notices his eyelids drooping. Many people also experience microsleep episodes during sleep deprivation, in which they sleep for periods of seconds to fractions of a second and frequently don't remember these episodes. A microsleep is an episode of Sleep lasting for a fraction of a second or up to a few seconds Because microsleep is frequently not remembered, microsleep or a related phenomenon may be responsible for lack of sleep and/or lack of memory in individuals like Nesterchuk and Thai Ngoc.
3. Randy Gardner holds the Guinness World Record for intentionally having gone the longest without sleep. Randy Gardner once held the scientifically documented record for the longest period of time a human being has intentionally gone without Sleep not using stimulants of any kind Guinness World Records, known until 2000 as The Guinness Book of Records (and in previous U In 1965, Gardner, then 18, stayed awake for 264 hours (about 11 days) for a high school science project. ^[40] He experienced significant deficits in concentration, motivation, perception and other higher mental processes during his sleep deprivation. However, he recovered normal cognitive functions after a few nights' sleep.
4. On May 25, 2007 the BBC reported that Tony Wright beat the Guinness World Record by staying awake for 11 days and nights. Events 1085 - Alfonso VI of Castile takes Toledo Spain back from the Moors. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. ^[41] The Guinness Book of Records has, however, withdrawn its backing of a sleep deprivation class because of the associated health risks.
5. A 3-year-old boy named Rhett Lamb of St. Petersburg Florida has a rare condition and has only slept for one to two hours per day in the past three years. He has a rare abnormality called an Arnold-Chiari malformation where brain tissue protrudes into the spinal canal. Arnold-Chiari malformation is a malformation of the Brain. It consists of a downward displacement of the Cerebellar tonsils and the Medulla through The skull puts pressure on the protruding part of the brain. It is not yet known if the brain malformation is directly related to his sleep deprivation. Rhett checked into a hospital for an experimental surgery to relieve the issue.

See also

Common sleeping positions, practices, and rituals

• Co-sleeping
• Hypnosis
• Meditation
• Neutral spine
• Sleep hygiene
• Yoga Nidra

Other

• Microsleep
• Morvan's syndrome
• Alarm clock
• Dream world (plot device)
• Sudden infant death syndrome

References

Further reading

• Bar-Yam, Yaneer (2003). "Chapter 3", Dynamics of Complex Systems (PDF).  
• Foldvary-Schaefer N, Grigg-Damberger M (Feb 2006). "Sleep and epilepsy: what we know, don't know, and need to know. ". J Clin Neurophysiol 23 (1): 4–20. PMID 16514348.  
• Gilmartin G, Thomas R (Nov 2004). "Mechanisms of arousal from sleep and their consequences. ". Curr Opin Pulm Med 10 (6): 468-74. doi:10.1097/01.mcp.0000143690.94442.b3. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 15510052.   [Review]
• Gottlieb D, Punjabi N, Newman A, Resnick H, Redline S, Baldwin C, Nieto F (Apr 25 2005). "Association of sleep time with diabetes mellitus and impaired glucose tolerance. ". Arch Intern Med 165 (8): 863-7. doi:10.1001/archinte.165.8.863. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 15851636.  
• Legramante J, Galante A (Aug 9 2005). "Sleep and hypertension: a challenge for the autonomic regulation of the cardiovascular system. ". Circulation 112 (6): 786-8. doi:10.1161/CIRCULATIONAHA.105.555714. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 16087808.   [Editorial]
• Feinberg I. Changes in sleep cycle patterns with age J Psychiatr Res. 1974;10:283–306. [review]
• Tamar Shochat and Sonia Ancoli - Specific Clinical Patterns in Aging - Sleep and Sleep Disorders [website]
• Zepelin H. Normal age related changes in sleep. In: Chase M, Weitzman ED, eds. Sleep Disorders: Basic and Clinical Research. New York: SP Medical; 1983:431–434.
• Morrissey M, Duntley S, Anch A, Nonneman R (2004). "Active sleep and its role in the prevention of apoptosis in the developing brain. ". Med Hypotheses 62 (6): 876-9. doi:10.1016/j.mehy.2004.01.014. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 15142640.  
• Marks G, Shaffery J, Oksenberg A, Speciale S, Roffwarg H (Jul-Aug 1995). "A functional role for REM sleep in brain maturation. ". Behav Brain Res 69 (1–2): 1–11. doi:10.1016/0166-4328(95)00018-O. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 7546299.  
• Mirmiran M, Scholtens J, van de Poll N, Uylings H, van der Gugten J, Boer G (Apr 1983). "Effects of experimental suppression of active (REM) sleep during early development upon adult brain and behavior in the rat. ". Brain Res 283 (2–3): 277-86. PMID 6850353.  
• Zhang, J. (Dec 2004). "[Memory process and the function of sleep]" (PDF). Journal of Theoretics 6 (6).  

External links

• American Academy of Sleep Medicine
• Sleep Research Society
• National Sleep Foundation
• National Center on Sleep Disorders Research

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