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An isolation tank is a lightless, soundproof tank inside which subjects float in salt water at skin temperature. They were first used by John C. Lilly in 1954 to test the effects of sensory deprivation. Such tanks are now also used for meditation and relaxation and in alternative medicine. The isolation tank was originally called the sensory deprivation tank. Other names for the isolation tank include flotation tank, float tank, John C. Lilly tank, REST tank, and sensory attenuation tank.
The isolation tank was developed in 1954 by John C. Lilly, a medical practitioner and neuropsychiatrist. During his training in psychoanalysis at the US National Institute of Mental Health (NIMH), Lilly experimented with sensory deprivation. After 10 years of experimentation without taking any psychoactive substances, he tried floating in combination with a psychedelic agent, mostly LSD (at that time he was a researcher at NIMH, and LSD was legal in the US). He found that floating alone, without taking any substances, was a much better experience because of non-disturbed consciousness.
In neurophysiology, there had been an open question about what keeps the brain going and the origin of its energy sources. One hypothesis was that the energy sources are biological and internal and do not depend upon the outside environment. It was argued that if all stimuli are cut off to the brain then the brain would go to sleep. Lilly decided to test this hypothesis and, with this in mind, created an environment which isolated an individual from external stimulation. From here, he studied the origin of consciousness and its relation to the brain.
Peter Suedfeld and Roderick Borrie of the University of British Columbia began experimenting on the therapeutic benefits of isolation tanks in the late 1970s. They named their technique "Restricted Environmental Stimulation Therapy" (REST).
Tank design and usage
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Initial isolation tanks were uncomfortable. Users were entirely submerged in the tank, which required them to wear a breathing apparatus and tight clothing. Users complained that the discomfort from the mask and clothing distracted from the isolation experience and that complete submersion led to fear of drowning. In current tanks, users are not submerged; instead, they float. This is done with a solution of epsom salt that increases water density, allowing the human body to float. Users float face-up in a relaxed position, with the face above the water and the ears submerged. This reduces the user's hearing, particularly when using ear-plugs as protection against the salt water. Users are encouraged to let their arms float to the side to further reduce skin sensation. This occurs because the air and water are the same temperature as the skin, and the feeling of a body boundary fades. The user's sense of smell is also greatly reduced, especially if the water has not been treated with chlorine. The density of the water prevents rolling over, even if asleep.
Another difference between early designs and current tanks is that tanks now face increased regulation of disinfection. In America, different states have implemented different rules. In Europe, the DIN 19643 bathing water standard requires automated chlorination controlled by REDOX (ORP) measurement. Chlorine, bromine and peroxide disinfection have all been used successfully. Most isolation tanks use a surface skimmer, cartridge filtration as a means of disinfection, and ultraviolet sterilization and chemicals to keep the water free of microbes and sediment. These machines are usually turned off during a session to keep the isolation space as quiet as possible. A ring heating system can be used around the outer walls of the tank so that warm water rises around the edges of the pool, travels towards the center, and then sinks under the tank user. This very slow water convection flow helps to keep the user centered in the middle of the pool. The small waves caused by breathing also aid in centering the subject.
Isolation tank construction and plumbing is typically all plastic. In most cases, glass reinforced resins are used. High quality flotation tanks may use acrylic or medical stainless steel which is impervious to the high salt concentration and more importantly the disinfectants. Epsom salt is not corrosive in the way sodium chloride is, but unsealed stone and concrete surfaces outside the tank can be damaged by splashed or dripped salt water as the recrystallizing salt opens up cracks and fissures as it dries. Chlorine used as a disinfectant can attack some surfaces such as marble.
Having plumbing facilities immediately next to the tank is also helpful when the water must eventually be changed to prevent microbe growth. The plumbing, including the drain pipes, should be constructed of plastic to prevent deterioration from the salt. The salt concentration may need to be diluted when discarded, to prevent damage to small private wastewater plumbing systems.
Generally, users of isolation tanks enter the pool nude. Swimsuits are discouraged, as the elastic material can create uncomfortable compressed stress points on the skin during the session. Due to the high salt content, the water is rarely changed, and all users are expected to shower, wash with soap, and rinse clean prior to entering the tank to avoid getting oils from their skin into the tank. The user rinses again after a session to remove excess epsom salt from the skin. White vinegar can be used to remove excess salt from the ear canal and hair.
Types of sessions
A therapeutic session in a flotation tank typically lasts between an hour to an hour and a half. For the first forty minutes, it is reportedly possible to experience itching in various parts of the body (a phenomenon also reported to be common during the early stages of meditation). The last twenty minutes often end with a transition from beta or alpha brainwaves to theta, which typically occurs briefly before sleep and again at waking. In a float tank, the theta state can last indefinitely without the subject losing consciousness. Many use the extended theta state as a tool for enhanced creativity and problem solving or for super learning. The more often the tank is used the longer the theta period becomes.
Spas sometimes provide commercial float tanks for use in relaxation. Flotation therapy has been academically studied in the USA and in Sweden with published results showing reduction of both pain and stress. The relaxed state also involves lowered blood pressure and maximum blood flow.
Floating can be passive or active, depending on the purpose. For relaxation, one simply floats and 'clears the mind.' Active floating has many different techniques. One may perform meditation, mantras, self-hypnosis, utilize educational programs, etc. Flotation therapy may be used to complement medical, psychological, body work and healing methods.
Flotation therapy is therapy that is undertaken by floating in warm salt water in a float tank. It developed from the research work of John Lilly although he was not primarily interested in therapy, rather in the effect of sensory deprivation on the human brain and mind. People using early float tanks discovered that they enjoyed the experience and that the relaxed state was also a healing state for many conditions including stress, anxiety, pain, swelling, insomnia and jet lag. As a result, float tanks were produced for commercial uses and commercial float centers offering flotation therapy opened in several countries during the period from 1980 to the present day when there are hundreds of flotation centers in dozens of countries. In almost all cases these float centers offer wellness treatments and in particular the release of stress. The San Francisco Bay Area has seen recent growth in such centers. Just Float is the World's Largest Float Therapy Center located in Pasadena, CA with 11 float cabins.
Research into flotation therapy (as opposed to just the effect of isolation) began in the USA at Ohio State University. Floating has been shown to improve creativity in Jazz musicians, accuracy in rifle shooting, focus before academic examinations and stress relief, among others. Research in the U.S., Canada, and Sweden has demonstrated the therapeutic effect on stress and pain. The technique takes advantage of an innate, natural inclination to relax when floating at a comfortable temperature. The temperature is that which allows natural heat generation to escape without the need for muscle action to raise body temperature in homeostasis. The floating posture, usually the supine position (although the prone position with chin supported on elbows is recommended for pregnant women), allows all the postural muscles to relax. The water pressure on the immersed skin is lower than the blood pressure and thus blood flow continues in skin capillaries. This is in contrast to normal bed rest where local contact pressure inhibits blood flow requiring regular adjustment of posture. When people cannot adjust their posture in bed, e.g. in some illnesses, bed sores can result. When floating there is no tendency to adjust posture and a person can float immobile for many hours.
The natural tendency of the body in the floating posture at the correct temperature is to dilate the blood vessels, reducing the blood pressure and maximizing blood flow. The brain activity normally associated with postural muscles is reduced to a minimum. In this floating state, natural endorphins are released reducing pain. Lactic acid removal is accelerated. Flow in the lymphatic system is increased.
It might be noted that there is no "flotation therapist", although there is a need to instruct the floater and need to maintain the equipment in a safe condition. However, flotation therapy is compatible with other therapies as a preparation or conjunct activity. Examples include massage, talk therapy, and hypnosis.
Perceived stress can be correlated with increased levels of cortisol and in flotation therapy there is a natural tendency for cortisol to be reduced. For this reason, flotation therapy is one of the few noninvasive techniques available to manage stress when it is a factor in reducing a person's ability to cope with normal life. Flotation therapy is a fast technique in this respect. The Swedish research was based on 40 minute float sessions. This compares well with other management techniques such as long vacations.
There are some similarities with the age old long hot bath. However, the main differences are that in flotation sensory impressions are reduced, temperature is maintained at the correct level and the bath is large and dense enough to float without touching the sides or bottom of the float unit. These factors allow the individual to achieve much deeper level of relaxation, and therapeutic benefit, than would otherwise be possible.
Of the salt
Most float tanks use Epsom salt, magnesium sulfate, in high concentration so that the relative density of the solution is about 1.25. (Lilly recommended 1.3 but this requires operating very close to saturation with the risk of recrystallization). The density assists floating particularly making the head buoyant so that the nose and mouth are well out of the water for breathing.
Research undertaken at the Human Performance Laboratory at Karlstad University Sven-Åke Bood concludes that regular flotation tank sessions can provide significant relief for chronic stress-related ailments. Studies involving 140 people with long-term conditions such as anxiety, stress, depression and fibromyalgia found that more than three quarters experienced noticeable improvements.
Dr. Bood commented: "Through relaxing in floating tanks, people with long-term fibromyalgia, for instance, or depression and anxiety felt substantially better after only 12 treatments". Research targeted the effectiveness of flotation treatment with regard to stress related pain and anxiety over the period of seven weeks. 23 percent of the participants became entirely free of pain and 56 percent experienced clear improvement.
Peter Suefeld at the University of British Columbia and Arreed Barabasz at the Washington State University have carried out several studies on the use of Flotation REST and the enhancement of human performance. Through their studies, they have demonstrated enhancement of scientific creativity, instrument flight performance and piano performance.
Several studies of sports performance have produced positive results in sports such as basketball, tennis, skiing and dart throwing. The studies proved that Flotation REST always had a more powerful effect. Different Flotation REST conditions such as, wet or dry, or imagery vs. no imagery, all proved to be sufficiently powerful to affect a change in performance. “Barabasz suggests that because REST potentiates imagery while disrupting over learned psychological processes, the technique is especially suited not only for the acquisition of new im- proved skills but the unlearning of less adaptive ones.”
The physicist Richard Feynman's experiences in a sensory deprivation tank were documented in the popular book Surely You're Joking, Mr. Feynman!. Feynman was invited to try the isolation tank at John Lilly's home after Lilly attended one of Feynman's popular lectures on quantum mechanics.
In a number of recent videos on YouTube and his own podcast, American stand-up comedian and television celebrity Joe Rogan describes his personal experiences with isolation tanks and shares his insights into using them for various purposes, such as exploring the nature of consciousness and improving health and well being.
In the "Charlie Rules the World" episode of It's Always Sunny in Philadelphia, Dennis goes inside a sensory deprivation tank to answer questions about what reality is.
Using a metal Isolation tank in order to acquire an altered state of consciousness is the main plot event in the 1980 movie Altered States, an adaptation of the novel by the same name by Paddy Chayefsky.
It can be also seen in the video of the song I Need a Doctor by Dr. Dre.
In Tom Clancy's 1988 novel The Cardinal of the Kremlin, Sensory deprivation is used as a form of torture/interrogation. A Russian woman is placed in the tank while under sedation, and wakes unable to see, hear, or feel anything. Over the course of hours she comes to believe she has been buried alive, until upon hearing her name called, confesses to everything she has ever done wrong, including unwittingly spying against the Soviet Union.
In the pilot episode of the TV series Fringe, Dr. Walter Bishop put FBI Agent Olivia Dunham in a sensory deprivation/isolation tank to let her gain access to the consciousness of her comatose former lover Agent John Scott. Sensory deprivation tanks are used in multiple Fringe episodes.
The use of, and mention of, a sensory deprivation tank occurred on several early episodes of Frasier. It was one of Maris' few hobbies.
In the video game Guild Wars 2, the Sylvari villain Scarlet Briar loses her mind as a result of her time in an Asura inventor's Isolation Module, a magical isolation chamber. The player character also enters this Isolation Module, and sees a vision of the future.
In Peep Show (TV Series) Series 4, Episode 3, gym worker Eva is trapped in the flotation tank and turns on the alarm.
A deprivation tank is also used in a two part episode of House (TV Series) when trying to recall the events of a bus wreck he was in.
In Dean Koontz writing as Richard Paige in the novel The Door to December, a sensory deprivation chamber (along with other psychological experiments) is used on a young girl ultimately giving her paranormal powers
In Stranger Things, one of the main characters, Eleven, uses a Sensory Deprivation Chamber to make contact with and interact with "the upside down."
Similar to the Dean Koontz novel, Dark Visions: The Passion by L.J. Smith uses a deprivation tank to enhance psychic abilities--and sometimes to torture, as in the Lost Symbol. At one point in the story, it's revealed that the Zetes Institute uses a complete submersion tank, opting to use weights instead of Epsom salt to anchor the subject in the middle of the water. 
- Altered state of consciousness
- Dark retreat
- Prisoner's cinema
- Psychedelic experience
- Sensory deprivation
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- on YouTube
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