Out-of-body experience

From Wikipedia, the free encyclopedia

Artist's depiction of the separation stage of an out-of-body experience, which often precedes free movement

An out-of-body experience (OBE or sometimes OOBE) is an experience in which a person seems to perceive the world from a location outside their physical body. An OBE is a form of autoscopy (literally "seeing self"), although the term autoscopy more commonly refers to the pathological condition of seeing a second self, or doppelgänger.

The term out-of-body experience was introduced in 1943 by G. N. M. Tyrrell in his book Apparitions, and was adopted by researchers such as Celia Green and Robert Monroe as an alternative to belief-centric labels such as "astral projection", "soul travel", or "spirit walking". OBEs can be induced by brain traumas, sensory deprivation, near-death experiences, dissociative and psychedelic drugs, dehydration, sleep, and electrical stimulation of the brain,^[4] among others. It can also be deliberately induced by some. One in ten people have an OBE once, or more commonly, several times in their life.

Neuroscientists and psychologists regard OBEs as dissociative experiences arising from different psychological and neurological factors.

Spontaneous

During/near sleep

Those experiencing OBEs sometimes report (among other types of immediate and spontaneous experience) a preceding and initiating lucid-dream state. In many cases, people who claim to have had an OBE report being on the verge of sleep, or being already asleep shortly before the experience. A large percentage of these cases refer to situations where the sleep was not particularly deep (due to illness, noises in other rooms, emotional stress, exhaustion from overworking, frequent re-awakening, etc.). In most of these cases subjects perceive themselves as being awake; about half of them note a feeling of sleep paralysis.

Near-death experiences

Another form of spontaneous OBE is the near-death experience (NDE). Some subjects report having had an OBE at times of severe physical trauma such as near-drownings or major surgery. Near-death experiences may include subjective impressions of being outside the physical body, sometimes visions of deceased relatives and religious figures, and transcendence of ego and spatiotemporal boundaries. Typically the experience includes such factors as: a sense of being dead; a feeling of peace and painlessness; hearing of various non-physical sounds, an out-of-body experience; a tunnel experience (the sense of moving up or through a narrow passageway); encountering "beings of light" and a God-like figure or similar entities; being given a "life review", and a reluctance to return to life.

Resulting from extreme physical effort

Along the same lines as an NDE, extreme physical effort during activities such as high-altitude climbing and marathon running can induce OBEs. A sense of bilocation may be experienced, with both ground and air-based perspectives being experienced simultaneously.

Induced

Chemical

• OBEs can be induced by hallucinogens (particularly dissociatives) such as psilocybin, ketamine, DMT, MDA, and LSD.

Mental induction

• Falling asleep physically without losing awareness. The "Mind Awake, Body Asleep" state is widely suggested as a cause of OBEs, voluntary and otherwise. Thomas Edison used this state to tackle problems while working on his inventions. He would rest a silver dollar on his head while sitting with a metal bucket in a chair. As he drifted off, the coin would noisily fall into the bucket, restoring some of his alertness. OBE pioneer Sylvan Muldoon more simply used a forearm held perpendicular in bed as the falling object. Salvador Dalí was said to use a similar "paranoiac-critical" method to gain odd visions which inspired his paintings. Deliberately teetering between awake and asleep states is known to cause spontaneous trance episodes at the onset of sleep which are ultimately helpful when attempting to induce an OBE. By moving deeper and deeper into relaxation, one eventually encounters a "slipping" feeling if the mind is still alert. This slipping is reported to feel like leaving the physical body. Some consider progressive relaxation a passive form of sensory deprivation;
• Deep trance, meditation and visualization. The types of visualizations vary; some common analogies include climbing a rope to "pull out" of one's body, floating out of one's body, getting shot out of a cannon, and other similar approaches. This technique is considered hard to use for people who cannot properly relax. One example of such a technique is the popular Golden Dawn "Body of Light" Technique.

Mechanical induction

• Brainwave synchronization via audio/visual stimulation. Binaural beats can be used to induce specific brainwave frequencies, notably those predominant in various mind awake/body asleep states. Binaural induction of a "body asleep" 4 Hertz brainwave frequency was observed as effective by the Monroe Institute, and some authors consider binaural beats to be significantly supportive of OBE initiation when used in conjunction with other techniques. Simultaneous introduction of "mind awake" beta frequencies (detectable in the brains of normal, relaxed awakened individuals) was also observed as constructive. Another popular technology uses sinusoidal wave pulses to achieve similar results, and the drumming accompanying Native American religious ceremonies is also believed to have heightened receptivity to "other worlds" through brainwave entrainment mechanisms;
• Magnetic stimulation of the brain, as with the God helmet developed by Michael Persinger;
• Direct stimulation of the vestibular cortex;
• Electrical stimulation of the brain, particularly the temporoparietal junction (see Blanke study below);
• Sensory deprivation. This approach aims to induce intense disorientation by removal of space and time references. Flotation tanks or pink noise played through headphones are often employed for this purpose;
• Sensory overload, the opposite of sensory deprivation. The subject can for instance be rocked for a long time in a specially designed cradle, or submitted to light forms of torture, to cause the brain to shut itself off from all sensory input. Both conditions tend to cause confusion and this disorientation often permits the subject to experience vivid, ethereal out-of-body experiences;
• Strong g-forces that causes blood to drain from parts of the brain, as experienced for example in high-performance aircraft or high-G training for pilots and astronauts;
• An apparatus that uses a head-mounted display and a touch that confuses the sense of proprioception (and which can also create the sensation of additional limbs).

Theories of OBEs

Psychological

In the fields of cognitive science and psychology OBEs are considered dissociative experiences arising from different psychological and neurological factors. Scientists consider the OBE to be an experience from a mental state, like a dream or an altered state of consciousness without recourse to the paranormal.

Charles Richet (1887) held that OBEs are created by the subject's memory and imagination processes and are no different from dreams. James H. Hyslop (1912) wrote that OBEs occur when the activity of the subconscious mind dramatizes certain images to give the impression the subject is in a different physical location. Eugéne Osty (1930) considered OBEs to be nothing more than the product of imagination. Other early researchers (such as Schmeing, 1938) supported psychophysiological theories. G. N. M. Tyrrell interpreted OBEs as hallucinatory constructs relating to subconscious levels of personality.

Donovan Rawcliffe (1959) connected the OBE experience with psychosis and hysteria. Other researchers have discussed the phenomena of the OBE in terms of a distortion of the body image (Horowitz, 1970) and depersonalization (Whitlock, 1978).^[49][50] The psychologists Nandor Fodor (1959) and Jan Ehrenwald (1974) proposed that an OBE is a defense mechanism designed to deal with the threat of death. According to (Irin and Watt, 2007) Jan Ehrenwald had described the out-of-body experience (OBE) "as an imaginal confirmation of the question for immortality, a delusory attempt to assure ourselves that we possess a soul that exists independently of the physical body. The psychologists Donald Hebb (1960) and Cyril Burt (1968) wrote on the psychological interpretation of the OBE involving body image and visual imagery. Graham Reed (1974) suggested that the OBE is a stress reaction to a painful situation, such as the loss of love. John Palmer (1978) wrote that the OBE is a response to a body image change causing a threat to personal identity.

Carl Sagan (1977) and Barbara Honegger (1983) wrote that the OBE experience may be based on a rebirth fantasy or reliving of the birth process based on reports of tunnel-like passageways and a cord-like connection by some OBErs which they compared to an umbilical cord. Susan Blackmore (1978) came to the conclusion that the OBE is a hallucinatory fantasy as it has the characteristics of imaginary perceptions, perceptual distortions and fantasy-like perceptions of the self (such as having no body). Ronald Siegel (1980) also wrote that OBEs are hallucinatory fantasies.

Harvey Irwin (1985) presented a theory of the OBE involving attentional cognitive processes and somatic sensory activity. His theory involved a cognitive personality construct known as psychological absorption and gave instances of the classification of an OBE as examples of autoscopy, depersonalization and mental dissociation. The psychophysiologist Stephen Laberge (1985) has written that the explanation for OBEs can be found in lucid dreaming. David Hufford (1989) linked the OBE experience with a phenomenon he described as a nightmare waking experience, a type of sleep paralysis. Other scientists have also linked OBEs to cases of hypnagogia and sleep paralysis (cataplexy).

In case studies fantasy proneness has been shown to be higher among OBErs than those who have not had an OBE. The data has shown a link between the OBE experience in some cases to fantasy prone personality (FPP). In a case study involving 167 participants the findings revealed that those who claimed to have experienced the OBE were "more fantasy prone, higher in their belief in the paranormal and displayed greater somatoform dissociation." Research from studies has also suggested that OBEs are related to cognitive-perceptual schizotypy.

Terence Hines (2003) has written that spontaneous out-of-body experiences can be generated by artificial stimulation of the brain and this strongly suggests that the OBE experience is caused from "temporary, minor brain malfunctions, not by the person's spirit (or whatever) actually leaving the body." In a study review of neurological and neurocognitive data (Bünning and Blanke, 2005) wrote that OBEs are due to "functional disintegration of lower-level multisensory processing and abnormal higher-level self-processing at the temporoparietal junction." Some scientists suspect that OBEs are the result of a mismatch between visual and tactile signals.

Richard Wiseman (2011) has noted that OBE research has focused on finding a psychological explanation and "out-of-body experiences are not paranormal and do not provide evidence for the soul. Instead, they reveal something far more remarkable about the everyday workings of your brain and body." A study conducted by Jason Braithwaite and colleagues (2011) linked the OBE to "neural instabilities in the brain's temporal lobes and to errors in the body's sense of itself". Braithwaite et al. (2013) reported that the "current and dominant view is that the OBE occurs due to a temporary disruption in multi-sensory integration processes."

Paranormal

Writers within the fields of parapsychology and occultism have written that OBEs are not psychological and that a soul, spirit or subtle body can detach itself out of the body and visit distant locations. Out-of-the-body experiences were known during the Victorian period in spiritualist literature as "travelling clairvoyance". The psychical researcher Frederic Myers referred to the OBE as a "psychical excursion". An early study which described alleged cases of OBEs was the two volume Phantasms of the Living, published in 1886 by the psychical researchers Edmund Gurney, Myers and Frank Podmore. The book was largely criticized by the scientific community as the anecdotal reports lacked evidential substantiation in nearly every case.

A 19th-century illustration of Robert Blair's poem The Grave, depicting the soul leaving the body

The Theosophist Arthur Powell (1927) was an early author to advocate the subtle body theory of OBEs. Sylvan Muldoon (1936) embraced the concept of an etheric body to explain the OBE experience. The psychical researcher Ernesto Bozzano (1938) had also supported a similar view describing the phenomena of the OBE experience in terms of bilocation in which an "etheric body" can release itself from the physical body in rare circumstances. The subtle body theory was also supported by occult writers such as Ralph Shirley (1938), Benjamin Walker (1977) and Douglas Baker (1979). James Baker (1954) wrote that a mental body enters an "intercosmic region" during the OBE. Marilynn Hughes states that the experiences are the projection of the spiritual body from the physical for the purpose of the soul's purification. Robert Crookall in many publications supported the subtle body theory of OBEs.

The paranormal interpretation of OBEs has not been supported by all researchers within the study of parapsychology. Gardner Murphy (1961) wrote that OBEs are "not very far from the known terrain of general psychology, which we are beginning to understand more and more without recourse to the paranormal".

In the 1970s, Karlis Osis conducted many OBE experiments with the psychic Alex Tanous. For a series of these experiments he was asked whilst in an OBE state to try to identify coloured targets that were placed in remote locations. Osis reported that in 197 trials there were 114 hits. However, the controls to the experiments have been criticized and according to Susan Blackmore, the final result was not particularly significant as 108 hits would be expected by chance. Blackmore noted that the results provide "no evidence for accurate perception in the OBE".

In April 1977, a patient from Harborview Medical Center known as Maria claimed to have experienced an out-of-body experience. During her OBE she claimed to have floated outside her body and outside of the hospital. Maria would later tell her social worker Kimberly Clark that during the OBE she had observed a tennis shoe on the third floor window ledge to the north side of the building. Clark would go to the north wing of the building and by looking out of the window could see a tennis shoe on one of the ledges. Clark published the account in 1985. The story has since been used in many paranormal books as evidence a spirit can leave the body.

In 1996, Hayden Ebbern, Sean Mulligan and Barry Beyerstein visited the Medical Center to investigate the story. They placed a tennis shoe on the same ledge and discovered that the shoe was visible from within the building and could have easily been observed by a patient lying in bed. They also discovered the shoe was easily observable from outside the building and suggested that Maria may have overheard a comment about it during her three days in the hospital and incorporated it into her OBE. They concluded "Maria's story merely reveals the naiveté and the power of wishful thinking" from OBE researchers seeking a paranormal explanation. Clark did not publish the description of the case until seven years after it happened, casting doubt on the story. Richard Wiseman has said that although the story is not evidence for anything paranormal it has been "endlessly repeated by writers who either couldn't be bothered to check the facts, or were unwilling to present their readers with the more skeptical side of the story."

Studies of OBEs

Early collections of OBE cases had been made by Ernesto Bozzano (Italy) and Robert Crookall (UK). Crookall approached the subject from a spiritualistic position, and collected his cases predominantly from spiritualist newspapers such as the Psychic News, which appears to have biased his results in various ways. For example, the majority of his subjects reported seeing a cord connecting the physical body and its observing counterpart; whereas Green found that less than 4% of her subjects noticed anything of this sort, and some 80% reported feeling they were a "disembodied consciousness", with no external body at all.

The first extensive scientific study of OBEs was made by Celia Green (1968). She collected written, first-hand accounts from a total of 400 subjects, recruited by means of appeals in the mainstream media, and followed up by questionnaires. Her purpose was to provide a taxonomy of the different types of OBE, viewed simply as an anomalous perceptual experience or hallucination, while leaving open the question of whether some of the cases might incorporate information derived by extrasensory perception.

In 1999, at the 1st International Forum of Consciousness Research in Barcelona, International Academy of Consciousness research-practitioners Wagner Alegretti and Nanci Trivellato presented preliminary findings of an online survey on the out-of-body experience answered by internet users interested in the subject; therefore, not a sample representative of the general population.

1,007 (85%) of the first 1,185 respondents reported having had an OBE. 37% claimed to have had between two and ten OBEs. 5.5% claimed more than 100 such experiences. 45% of those who reported an OBE said they successfully induced at least one OBE by using a specific technique. 62% of participants claiming to have had an OBE also reported having enjoyed nonphysical flight; 40% reported experiencing the phenomenon of self-bilocation (i.e. seeing one's own physical body whilst outside the body); and 38% claimed having experienced self-permeability (passing through physical objects such as walls). The most commonly reported sensations experienced in connection with the OBE were falling, floating, repercussions e.g. myoclonia (the jerking of limbs, jerking awake), sinking, torpidity (numbness), intracranial sounds, tingling, clairvoyance, oscillation and serenity.

Another reported common sensation related to OBE was temporary or projective catalepsy, a more common feature of sleep paralysis. The sleep paralysis and OBE correlation was later corroborated by the Out-of-Body Experience and Arousal study published in Neurology by Kevin Nelson and his colleagues from the University of Kentucky in 2007. The study discovered that people who have out-of-body experiences are more likely to suffer from sleep paralysis.

Also noteworthy, is the Waterloo Unusual Sleep Experiences Questionnaire  that further illustrates the correlation. William Buhlman, an author on the subject, has conducted an informal but informative online survey.

In surveys, as many as 85% of respondents tell of hearing loud noises, known as "exploding head syndrome" (EHS), during the onset of OBEs.

Miss Z study

In 1968, Charles Tart conducted an OBE experiment with a subject known as Miss Z for four nights in his sleep laboratory. The subject was attached to an EEG machine and a five-digit code was placed on a shelf above her bed. She did not claim to see the number on the first three nights but on fourth gave the number correctly. The psychologist James Alcock criticized the experiment for inadequate controls and questioned why the subject was not visually monitored by a video camera. Martin Gardner has written the experiment was not evidence for an OBE and suggested that whilst Tart was "snoring behind the window, Miss Z simply stood up in bed, without detaching the electrodes, and peeked." Susan Blackmore wrote "If Miss Z had tried to climb up, the brain-wave record would have showed a pattern of interference. And that was exactly what it did show."

Neurology and OBE-like experiences

There are several possible physiological explanations for parts of the OBE. OBE-like experiences have been induced by stimulation of the brain. OBE-like experience has also been induced through stimulation of the posterior part of the right superior temporal gyrus in a patient. Positron-emission tomography was also used in this study to identify brain regions affected by this stimulation. The term OBE-like is used above because the experiences described in these experiments either lacked some of the clarity or details of normal OBEs, or were described by subjects who had never experienced an OBE before. Such subjects were therefore not qualified to make claims about the authenticity of the experimentally-induced OBE.

British psychologist Susan Blackmore and others suggest that an OBE begins when a person loses contact with sensory input from the body while remaining conscious. The person retains the illusion of having a body, but that perception is no longer derived from the senses. The perceived world may resemble the world he or she generally inhabits while awake, but this perception does not come from the senses either. The vivid body and world is made by our brain's ability to create fully convincing realms, even in the absence of sensory information. This process is witnessed by each of us every night in our dreams, though OBEs are claimed to be far more vivid than even a lucid dream.

Irwin pointed out that OBEs appear to occur under conditions of either very high or very low arousal. For example, Green found that three quarters of a group of 176 subjects reporting a single OBE were lying down at the time of the experience, and of these 12% considered they had been asleep when it started. By contrast, a substantial minority of her cases occurred under conditions of maximum arousal, such as a rock-climbing fall, a traffic accident, or childbirth. McCreery has suggested that this paradox may be explained by reference to the fact that sleep can supervene as a reaction to extreme stress or hyper-arousal. He proposes that OBEs under both conditions, relaxation and hyper-arousal, represent a form of "waking dream", or the intrusion of Stage 1 sleep processes into waking consciousness.

Olaf Blanke studies

Research by Olaf Blanke in Switzerland found that it is possible to reliably elicit experiences somewhat similar to the OBE by stimulating regions of the brain called the right temporal-parietal junction (TPJ; a region where the temporal lobe and parietal lobe of the brain come together). Blanke and his collaborators in Switzerland have explored the neural basis of OBEs by showing that they are reliably associated with lesions in the right TPJ region and that they can be reliably elicited with electrical stimulation of this region in a patient with epilepsy. These elicited experiences may include perceptions of transformations of the patient's arms and legs (complex somatosensory responses) and whole-body displacements (vestibular responses).

In neurologically normal subjects, Blanke and colleagues then showed that the conscious experience of the self and body being in the same location depends on multisensory integration in the TPJ. Using event-related potentials, Blanke and colleagues showed the selective activation of the TPJ 330–400 ms after stimulus onset when healthy volunteers imagined themselves in the position and visual perspective that generally are reported by people experiencing spontaneous OBEs. Transcranial magnetic stimulation in the same subjects impaired mental transformation of the participant's own body. No such effects were found with stimulation of another site or for imagined spatial transformations of external objects, suggesting the selective implication of the TPJ in mental imagery of one's own body.

In a follow up study, Arzy et al. showed that the location and timing of brain activation depended on whether mental imagery is performed with mentally embodied or disembodied self location. When subjects performed mental imagery with an embodied location, there was increased activation of a region called the "extrastriate body area" (EBA), but when subjects performed mental imagery with a disembodied location, as reported in OBEs, there was increased activation in the region of the TPJ. This leads Arzy et al. to argue that "these data show that distributed brain activity at the EBA and TPJ as well as their timing are crucial for the coding of the self as embodied and as spatially situated within the human body."

Blanke and colleagues thus propose that the right temporal-parietal junction is important for the sense of spatial location of the self, and that when these normal processes go awry, an OBE arises.

In August 2007 Blanke's lab published research in Science demonstrating that conflicting visual-somatosensory input in virtual reality could disrupt the spatial unity between the self and the body. During multisensory conflict, participants felt as if a virtual body seen in front of them was their own body and mislocalized themselves toward the virtual body, to a position outside their bodily borders. This indicates that spatial unity and bodily self-consciousness can be studied experimentally and is based on multisensory and cognitive processing of bodily information.

Ehrsson study

In August 2007, Henrik Ehrsson, then at the Institute of Neurology at University College of London (now at the Karolinska Institute in Sweden), published research in Science demonstrating the first experimental method that, according to the scientist's claims in the publication, induced an out-of-body experience in healthy participants. The experiment was conducted in the following way:

The study participant sits in a chair wearing a pair of head-mounted video displays. These have two small screens over each eye, which show a live film recorded by two video cameras placed beside each other two metres behind the participant's head. The image from the left video camera is presented on the left-eye display and the image from the right camera on the right-eye display. The participant sees these as one "stereoscopic" (3D) image, so they see their own back displayed from the perspective of someone sitting behind them.

The researcher then stands just beside the participant (in their view) and uses two plastic rods to simultaneously touch the participant's actual chest out-of-view and the chest of the illusory body, moving this second rod towards where the illusory chest would be located, just below the camera's view.

The participants confirmed that they had experienced sitting behind their physical body and looking at it from that location.

Both critics and the experimenter himself note that the study fell short of replicating "full-blown" OBEs. As with previous experiments which induced sensations of floating outside of the body, Ehrsson's work does not explain how a brain malfunction might cause an OBE. Essentially, Ehrsson created an illusion that fits a definition of an OBE in which "a person who is awake sees his or her body from a location outside the physical body."

Awareness during Resuscitation Study

In 2001, Sam Parnia and colleagues investigated out of body claims by placing figures on suspended boards facing the ceiling, not visible from the floor. Parnia wrote "anybody who claimed to have left their body and be near the ceiling during resuscitation attempts would be expected to identify those targets. If, however, such perceptions are psychological, then one would obviously not expect the targets to be identified." The philosopher Keith Augustine, who examined Parnia's study, has written that all target identification experiments have produced negative results. Psychologist Chris French wrote regarding the study "unfortunately, and somewhat atypically, none of the survivors in this sample experienced an OBE."

In the autumn of 2008, 25 UK and US hospitals began participation in a study, coordinated by Sam Parnia and Southampton University known as the AWARE study (AWAreness during REsuscitation). Following on from the work of Pim van Lommel in the Netherlands, the study aims to examine near-death experiences in 1,500 cardiac arrest survivors and so determine whether people without a heartbeat or brain activity can have documentable out-of-body experiences. As part of the study Parnia and colleagues have investigated out of body claims by using hidden targets placed on shelves that could only be seen from above. Parnia has written "if no one sees the pictures, it shows these experiences are illusions or false memories".

In 2014 Parnia issued a statement indicating that the first phase of the project has been completed and the results are undergoing peer review for publication in a medical journal. No subjects saw the images mounted out of sight according to Parnia's early report of the results of the study at an American Heart Association meeting in November 2013. Only two out of the 152 patients reported any visual experiences, and one of them described events that could be verified. The two NDEs occurred in an area were "no visual targets had been placed".

On October 6, 2014, the results of the study were published in the journal Resuscitation. Among those who reported a perception of awareness and completed further interviews, 46 per cent experienced a broad range of mental recollections in relation to death that were not compatible with the commonly used term of NDEs. These included fearful and persecutory experiences. Only 9 per cent had experiences compatible with NDEs and 2 per cent exhibited full awareness compatible with OBEs with explicit recall of 'seeing' and 'hearing' events. One case was validated and timed using auditory stimuli during cardiac arrest. According to Caroline Watt "The one 'verifiable period of conscious awareness' that Parnia was able to report did not relate to this objective test. Rather, it was a patient giving a supposedly accurate report of events during his resuscitation. He didn't identify the pictures, he described the defibrillator machine noise. But that's not very impressive since many people know what goes on in an emergency room setting from seeing recreations on television."

AWARE Study II

As of May 2016, a posting at the UK Clinical Trials Gateway website describes plans for AWARE II, a two-year multicenter observational study of 900-1500 patients experiencing cardiac arrest, with subjects being recruited as August 1, 2014 and a trial end date of May 31, 2017.

Smith & Messier

A recent functional imaging study reported the case of a woman who could experience out of body experience at will. She reported developing the ability as a child and associated it with difficulties in falling sleep. Her OBEs continued into adulthood but became less frequent. She was able to see herself rotating in the air above her body, lying flat, and rolling in the horizontal plane. She reported sometimes watching herself move from above but remained aware of her unmoving "real" body. The participant reported no particular emotions linked to the experience. "[T]he brain functional changes associated with the reported extra-corporeal experience (ECE) were different than those observed in motor imagery. Activations were mainly left-sided and involved the left supplementary motor area and supramarginal and posterior superior temporal gyri, the last two overlapping with the temporal parietal junction that has been associated with out-of-body experiences. The cerebellum also showed activation that is consistent with the participant's report of the impression of movement during the ECE. There was also left middle and superior orbital frontal gyri activity, regions often associated with action monitoring."

OBE training and research facilities

The Monroe Institute's Nancy Penn Center is a facility specializing in or out-of-body experience induction. The Center for Higher Studies of the Consciousness in Brazil is another large OBE training facility. The International Academy of Consciousness in southern Portugal features the Projectarium, a spherical structure dedicated exclusively for practice and research on out-of-body experience. Olaf Blanke's Laboratory of Cognitive Neuroscience has become a well-known laboratory for OBE research.

Astral projection

Astral projection is a paranormal interpretation of out-of-body experiences that assumes the existence of one or more non-physical planes of existence and an associated body beyond the physical. Commonly such planes are called astral, etheric, or spiritual. Astral projection is often experienced as the spirit or astral body leaving the physical body to travel in the spirit world or astral plane.

Somatosensory system

From Wikipedia, the free encyclopedia

The somatosensory system is a part of the sensory nervous system. The somatosensory system is a complex system of sensory neurons and pathways that responds to changes at the surface or inside the body. The axons (as afferent nerve fibers), of sensory neurons connect with, or respond to, various receptor cells. These sensory receptor cells are activated by different stimuli such as heat and nociception, giving a functional name to the responding sensory neuron, such as a thermoreceptor which carries information about temperature changes. Other types include mechanoreceptors, chemoreceptors, and nociceptors and they send signals along a sensory nerve to the spinal cord where they may be processed by other sensory neurons and then relayed to the brain for further processing. Sensory receptors are found all over the body including the skin, epithelial tissues, muscles, bones and joints, internal organs, and the cardiovascular system.

Touch is a crucial means of receiving information. This photo shows tactile markings identifying stairs for visually impaired people.

Somatic senses are sometimes referred to as somesthetic senses, with the understanding that somesthesis includes the sense of touch, proprioception (sense of position and movement), and (depending on usage) haptic perception.

The mapping of the body surfaces in the brain is called somatotopy. In the cortex, it is also referred to as the cortical homunculus. This brain-surface ("cortical") map is not immutable, however. Dramatic shifts can occur in response to stroke or injury.

System overview

This diagram linearly (unless otherwise mentioned) tracks the projections of all known structures that allow for touch to their relevant endpoints in the human brain.

Mechanical

The four mechanoreceptors in the skin each respond to different stimuli for short or long periods.
Merkel cell nerve endings are found in the basal epidermis and hair follicles; they react to low vibrations (5–15 Hz) and deep static touch such as shapes and edges. Due to a small receptive field (extremely detailed info) they are used in areas like fingertips the most; they are not covered (shelled) and thus respond to pressures over long periods.

Tactile corpuscles react to moderate vibration (10–50 Hz) and light touch. They are located in the dermal papillae; due to their reactivity they are primarily located in fingertips and lips. They respond in quick action potentials, unlike Merkel. They are responsible for the ability to read Braille and feel gentle stimuli.

Lamellar corpuscles determine gross touch and distinguish rough and soft substances. They react in quick action potentials, especially to vibrations around 250 Hz (even up to centimeters away). They are the most sensitive to vibrations, and have large receptor fields. Pacinian reacts only to sudden stimuli so pressures like clothes that are always compressing their shape are quickly ignored.

Bulbous corpuscles react slowly and respond to sustained skin stretch. They are responsible for the feeling of object slippage and play a major role in the kinesthetic sense and control of finger position and movement. Merkel and bulbous cells - slow-response - are myelinated; the rest - fast-response - are not. All of these receptors are activated upon pressures that squish their shape causing an action potential.

Neural

Gray's Anatomy, figure 759: the sensory tract, showing the pathway (blue) up the spinal cord, through the somatosensory thalamus, to S1 (Brodmann areas 3, 1, and 2), S2, and BA7

 

Gray's Anatomy, figure 717: detail showing path adjacent to the insular cortex (marked insula in this figure), adjacent to S1, S2, and BA7

All afferent touch/vibration info ascends the spinal cord via the posterior (dorsal) column-medial lemniscus pathway via gracilis (T7 and below) or cuneatus (T6 and above).

Cuneatus sends signals to the cochlear nucleus indirectly via spinal grey matter, this info is used in determining if a perceived sound is just villi noise/irritation. All fibers cross (left becomes right) in the medulla.

The postcentral gyrus includes the primary somatosensory cortex (Brodmann areas 3, 2 and 1) collectively referred to as S1.

BA3 receives the densest projections from the thalamus. BA3a is involved with the sense of relative position of neighboring body parts and amount of effort being used during movement. BA3b is responsible for distributing somato info, it projects texture info to BA1 and shape + size info to BA2.

Region S2 (secondary somatosensory cortex) divides into Area S2 and parietal ventral area. Area S2 is involved with specific touch perception and is thus integrally linked with the amygdala and hippocampus to encode and reinforce memories.

Parietal ventral area is the somatosensory relay to the premotor cortex and somatosensory memory hub, BA5.

BA5 is the topographically organized somato memory field and association area.

BA1 processes texture info while BA2 processes size + shape info.

Area S2 processes light touch, pain, visceral sensation, and tactile attention.

S1 processes the remaining info (crude touch, pain, temperature).

BA7 integrates visual and proprioceptive info to locate objects in space.

The insular cortex (insula) plays a role in the sense of bodily-ownership, bodily self-awareness, and perception. Insula also plays a role in conveying info about sensual touch, pain, temperature, itch, and local oxygen status. Insula is a highly connected relay and thus is involved in numerous functions.

Structure

The somatosensory system is spread through all major parts of the vertebrate body. It consists both of sensory receptors and afferent neurons in the periphery (skin, muscle and organs for example), to deeper neurons within the central nervous system.

General somatosensory pathway

A somatosensory pathway will typically have three long neurons: primary, secondary, and tertiary (or first, second, and third):

1. The first neuron always has its cell body in the dorsal root ganglion of the spinal nerve (if sensation is in parts of the head or neck not covered by the cervical nerves, it will be the trigeminal nerve ganglia or the ganglia of other sensory cranial nerves);
2. The second neuron has its cell body either in the spinal cord or in the brainstem. This neuron's ascending axons will cross (decussate) to the opposite side either in the spinal cord or in the brainstem;
3. In the case of touch and certain types of pain, the third neuron has its cell body in the VPN of the thalamus and ends in the postcentral gyrus of the parietal lobe.

Touch can result in many different physiological reactions. Here, a baby laughs at being tickled by an older sister.

Photoreceptors, similar to those found in the retina of the eye, detect potentially damaging ultraviolet radiation (ultraviolet A specifically), inducing increased production of melanin by melanocytes. Thus tanning potentially offers the skin rapid protection from DNA damage and sunburn caused by ultraviolet radiation (DNA damage caused by ultraviolet B). However, whether this offers protection is debatable, because the amount of melanin released by this process is modest in comparison to the amounts released in response to DNA damage caused by ultraviolet B radiation.

Tactile feedback

The tactile feedback from proprioception is derived from the proprioceptors in the skin, muscles, and joints.

Balance

The receptor for the sense of balance resides in the vestibular system in the ear (for the three-dimensional orientation of the head, and by inference, the rest of the body). Balance is also mediated by the kinesthetic reflex fed by proprioception (which senses the relative location of the rest of the body to the head). In addition, proprioception estimates the location of objects which are sensed by the visual system (which provides confirmation of the place of those objects relative to the body), as input to the mechanical reflexes of the body.

Fine touch and crude touch

The cortical homunculus, a map of somatosensory areas of the brain, was devised by Wilder Penfield.

Fine touch (or discriminative touch) is a sensory modality that allows a subject to sense and localize touch. The form of touch where localization is not possible is known as crude touch. The posterior column–medial lemniscus pathway is the pathway responsible for the sending of fine touch information to the cerebral cortex of the brain.

Crude touch (or non-discriminative touch) is a sensory modality that allows the subject to sense that something has touched them, without being able to localize where they were touched (contrasting "fine touch"). Its fibres are carried in the spinothalamic tract, unlike the fine touch, which is carried in the dorsal column.  As fine touch normally works in parallel to crude touch, a person will be able to localize touch until fibres carrying fine touch (Posterior column–medial lemniscus pathway) have been disrupted. Then the subject will feel the touch, but be unable to identify where they were touched.

Neural processing of social touch

The somatosensory cortex encodes incoming sensory information from receptors all over the body. Affective touch is a type of sensory information that elicits an emotional reaction and is usually social in nature, such as a physical human touch. This type of information is actually coded differently than other sensory information. Intensity of affective touch is still encoded in the primary somatosensory cortex and is processed in a similar way to emotions invoked by sight and sound, as exemplified by the increase of adrenaline caused by the social touch of a loved one, as opposed to the physical inability to touch someone you don't love.

Meanwhile, the feeling of pleasantness associated with affective touch activates the anterior cingulate cortex more than the primary somatosensory cortex. Functional magnetic resonance imaging (fMRI) data shows that increased blood oxygen level contrast (BOLD) signal in the anterior cingulate cortex as well as the prefrontal cortex is highly correlated with pleasantness scores of an affective touch. Inhibitory transcranial magnetic stimulation (TMS) of the primary somatosensory cortex inhibits the perception of affective touch intensity, but not affective touch pleasantness. Therefore, the S1 is not directly involved in processing socially affective touch pleasantness, but still plays a role in discriminating touch location and intensity.

Individual variation

A variety of studies have measured and investigated the causes for differences between individuals in the sense of fine touch. One well-studied area is passive tactile spatial acuity, the ability to resolve the fine spatial details of an object pressed against the stationary skin. A variety of methods have been used to measure passive tactile spatial acuity, perhaps the most rigorous being the grating orientation task. In this task subjects identify the orientation of a grooved surface presented in two different orientations, which can be applied manually or with automated equipment. Many studies have shown a decline in passive tactile spatial acuity with age; the reasons for this decline are unknown, but may include loss of tactile receptors during normal aging. Remarkably, index finger passive tactile spatial acuity is better among adults with smaller index fingertips; this effect of finger size has been shown to underlie the better passive tactile spatial acuity of women, on average, compared to men. The density of tactile corpuscles, a type of mechanoreceptor that detects low-frequency vibrations, is greater in smaller fingers; the same may hold for Merkel cells, which detect the static indentations important for fine spatial acuity. Among children of the same age, those with smaller fingers also tend to have better tactile acuity. Many studies have shown that passive tactile spatial acuity is enhanced among blind individuals compared to sighted individuals of the same age, possibly because of cross modal plasticity in the cerebral cortex of blind individuals. Perhaps also due to cortical plasticity, individuals who have been blind since birth reportedly consolidate tactile information more rapidly than sighted people.

Clinical significance

A somatosensory deficiency may be caused by a peripheral neuropathy involving peripheral nerves of the somatosensory system. This may present as numbness or paresthesia.

Society and culture

Haptic technology can provide touch sensation in virtual and real environments. In the field of speech therapy, tactile feedback can be used to treat speech disorders.

Temporoparietal junction

From Wikipedia, the free encyclopedia

Temporoparietal junction
Side view of the human brain. TPJ is indicated by red circle.
Side view of the human brain. TPJ is indicated by red circle.
Identifiers
Acronym(s)	TPJ

The temporoparietal junction (TPJ) is an area of the brain where the temporal and parietal lobes meet, at the posterior end of the Sylvian fissure. The TPJ incorporates information from the thalamus and the limbic system, as well as from the visual, auditory, and somatosensory systems. The TPJ also integrates information from both the external environment as well as from within the body. The TPJ is responsible for collecting all of this information and then processing it. This area is also known to play a crucial role in self-other distinctions processes and theory of mind (ToM). Furthermore, damage to the TPJ has been implicated in having adverse effects on an individual’s ability to make moral decisions and has been known to produce out-of-body experiences (OBEs). Electromagnetic stimulation of the TPJ can also cause these effects. Apart from these diverse roles that the TPJ plays, it is also known for its involvement in a variety of widespread disorders including amnesia, Alzheimer's disease, and schizophrenia.

Anatomy and function

Animation. Both left and right temporoparietal junctions are shown in red.

The brain contains four main lobes: temporal lobe, parietal lobe, frontal lobe and the occipital lobe. The temporoparietal junction lies in the region between the temporal and parietal lobes, near the Sylvian fissure. Specifically, it is composed of the inferior parietal lobule and the caudal parts of the superior temporal sulcus. There are two halves to the temporoparietal junction, with each component in their respective hemispheres of the brain. Each half of the TPJ pertains to various aspects of cognitive function. Often, however, the separate halves of the TPJ will work in coordination. The TPJ is mainly involved in information processing and perception.

Right temporoparietal junction

The right temporoparietal junction (rTPJ) is involved in the processing of information in terms of the ability of an individual to pay attention. Evidence from neuroimaging studies as well as lesion studies revealed that the rTPJ plays a pivotal role in analyzing signals from self-produced actions as well as with signals from the external environment. For example, an individual with lesions in their rTPJ would more than likely exhibit a sense of hemi-neglect, wherein they would no longer be able to pay attention to anything they observe on the left. So, if someone were to have a lesion in their rTPJ, then over time the awareness of the left limbs may fade without treatment. Visual signals provide the sensory information necessary for the brain to process spatial recognition of the world. When vision is limited, knowledge of existence begins to fade away since as far as the brain is concerned the object does not exist. Furthermore, the rTPJ plays a role in the way individuals observe and process information, thus impacting social interaction. Empathy and sympathy require an individual to simultaneously distinguish between different possible perspectives on the same situation. Imaging studies show that this ability depends upon the coordinated interaction of the rTPJ to identify and process the social cues presented to it. This rapid process allows for an individual to quickly react to situations.

Left temporoparietal junction

The left temporoparietal junction (lTPJ) contains both Wernicke's area and the angular gyrus, both prominent anatomical structures of the brain that are involved in language cognition, processing, and comprehension of both written and spoken language. This is the region of the brain wherein “Mentalese”, a term coined by Steven Pinker to explain the brain’s language that translates itself into written and spoken language, is processed. According to Pinker, “knowing a language is knowing how to translate Mentalese into a string of words and vice versa.” The lTPJ succeeds in this matter by taking in observations from external environments, such as conversations, making connections in the brain regarding past memories or incidents and then converting those thoughts and connections to written and spoken language. Pinker explains this in detail in The Language Instinct: How the Mind Creates Language. The lTPJ also plays an important role in reasoning of other’s beliefs, intentions, and desires. Activation of the lTPJ was observed in patients processing mental states such as beliefs when an fMRI was used on patients as they were asked to make inferences regarding the mental states of others such as lying. This study was further supplemented by a study which identified that lesions to the left TPJ can impair cognitive processes specifically involved in the inference of someone else's belief, intention, or desire. Individuals with lesions in the lTPJ were no longer able to correctly identify when someone was lying or insinuating a false sense of belief or desire. The lTPJ is also involved in the processing of associating and remembering the names of individuals and objects.

Disorders

The dopaminergic-serotonergic system mediates our ability to distinguish and understand others beliefs as well as predict their behavior in light of that understanding. In certain disorders, involving the dopaminergic-serotonergic system, this mentalizing process is disrupted and part or all of the process is impaired; this includes amnesia and Alzheimer's disease, and schizophrenia.

Amnesia

Amnesia is a deficit in memory caused by brain damage, disease, or physiological trauma. Amnesia is best understood via Henry Molaison, or patient H.M. Molaison, who suffered from severe epilepsy and eventually had a temporal lobectomy. After surgery, his epilepsy improved but then he had anterograde amnesia, wherein long-term memory formation is inhibited. Short-term memory remained normal except that he could never remember anything that had happened after his surgery for very long. Based on general known roles of the TPJ, it is known that the TPJ is involved in the memory processing system of the body. Studies have also revealed that certain types of epileptic amnesia could be attributed to TPJ. fMRI studies indicated that there was lower activation of the rTPJ in patients with epileptic amnesia. Furthermore, it was noticed the autobiographical memories were affected in these patients. As such, the rTPJ along with the right cerebellum were identified as core components of autobiographical memory.

In terms of treatment, most forms of amnesia fix themselves without actually undergoing treatment. However, options such as cognitive therapy or occupational therapy have proved to help. Therapy will focus on various methods to improve a patient’s memory and with repetition over time, a patient’s memory as a whole will improve and eventually become close to normal.

Alzheimer's disease

Alzheimer’s disease is the most common form of dementia and is also the sixth leading cause of death in the United States. This disease has no known cure and is a disease that worsens as it progresses and eventually leads to death. Reduced metabolism in the TPJ, along with the superior frontal sulcus, correlates with Alzheimer’s patients’ inability to perceive themselves as others do (with a third-person point of view); the discrepancy between a patients’ understanding of their own cognitive impairment and the actual extent of their cognitive impairment increases as metabolism in the TPJ decreases. Additionally, the TPJ contains the praxicon, a dictionary of representations of different human actions, which is necessary to distinguishing between actions of the self and other people. Because Alzheimer’s patients, as well as patients with other forms of dementia, with anosognosia are unable to distinguish between the normal actions of other people and their own diminished abilities, it is expected that there must be damage to the TPJ that is arresting this cognitive function.

In terms of treatment options for managing the symptoms of Alzheimer’s, current options include pharmaceuticals, psychosocial intervention, caregiving, and feeding tubes. Current pharmaceuticals are either acetylcholinesterase inhibitors or an NMDA receptor antagonist. Psychosocial interventions are used to supplement pharmaceutical usage as it can take some time to get used to. Since Alzheimer’s disease does eventually lead to death with the condition worsening over time, all family members can really do is provide care for those afflicted and try to make their lives as easy as possible as the situation worsens.

Autism spectrum disorder

There is a connection between the temporoparietal junction and the ability to recognize socially awkward situations in individuals with autism spectrum disorder. Both neurotypical and autism spectrum disorder participants were asked to watch socially-awkward situations (a full-length episode of the sitcom The Office) under an fMRI which measured their brain activity. During this experiment several brain regions should be activated which involve social cognition and perception such as superior temporal gyrus, frontal gyrus, temporoparietal junction, parietal lobe, and amygdala. However, participants with autism spectrum disorder displayed a difference in activation when compared to the neurotypical individuals in their temporoparietal junction during the fMRI. Thus, participants with autism spectrum disorder have a hard time identifying socially- awkward situations since the temporoparietal junctions plays a role in social cognition and perception.  Recently, an analysis of a huge multi-centre dataset confirmed significant differences at this and other locations.

Schizophrenia

The decreased ability for schizophrenia patients to function in social situations has been related to a deficit within the theory of mind process. There have been relatively few studies that have examined the role of theory of mind in schizophrenia patients; the findings of these studies as they relate to the activation of the TPJ are varied. Some studies have found decreased activation of the TPJ in schizophrenia patients who were asked to make inferences about other peoples' social intentions based on cartoons; other studies, however, performed similar assessments of schizophrenia patients and found that the TPJ actually became hyperactive, compared to control individuals without schizophrenia, in the TPJ. This indicates that there is abnormal activation of the TPJ in these patients while performing tasks that involving understanding social intention of others, but the directionality of this abnormal activity is not clear, or possibly not universal throughout schizophrenia patients. It was found that the changes in activation in the TPJ were lateralized; they found that there was reduced activity in only the right TPJ and proposed that based on previous research about the different roles of the right and left TPJ the findings indicated that there was a more general deficit in the overall mentalizing process for these patients, but their ability to understand other individuals' basic social intentions through observing interaction is not impaired.

A study found that there was a connection between the auditory hallucinations in schizophrenia and the TPJ; the TPJ has been determined as a critical node in the auditory-verbal hallucination system. This study found that there was a significant decrease in the connectivity between the left TPJ and the right hemispheric homotope of the Broca's area, which is related to the production of language that is also characteristic of AVH events. This aspect of impairment seen in schizophrenia patients may also be related to the involvement of the TPJ with producing out of body experiences.

Anxiety Disorders

A recent study showed reduced activity in the TPJ of adolescents compared to adults during an extinction task, suggesting a role for the TPJ in anxiety disorders.

Future of possible treatments

Vasopressin is a neuropeptide that is involved in regulating social behaviors, including social memory and recognition. One study examined the connection between vasopressin and cortical areas that are involved in processing social interactions including the TPJ. This study looked specifically at the brain regions that were active in men who were given vasopressin and tested based on familiarity related tasks. They found that the introduction of vasopressin caused a localized specific change in social recognition-related activity in the left TPJ/Brodmann area 39; the presence of vasopressin diminishes the heightened activity in the left TPJ that is present upon exposure to an unfamiliar social stimulus indicating that the presence of vasopressin leads individuals to associate an unfamiliar face with a familiar category more readily. While recognizing that this is the first study that has looked into this connection, the authors propose that it has potential to lead into further research about regulating the TPJ with vasopressin or a similar compound, which could allow pharmacologists to target this area of the brain and help with certain disorders including autism, social anxiety disorder. Perhaps such an approach could also be used to treat certain symptoms of schizophrenia or other disorders with know social cognitive impairments.

Current research

Current research involving the TPJ is extensive, ranging from issues of physiology to issues of mental state. A wide range of cognitive processes rely on the TPJ and as such gaining information about it is crucial. Research is conducted by studying the role TPJ plays both with and without lesions when stimulated. Research concerns various issues such as theory of mind, out-of-body experiences, temporal order judgments, morality, etc. This is a growing field due to the prevalence of ailments that involve TPJ as well as because of the importance of perception in everyday life.

Theory of mind

Theory of mind requires the collaboration of functionally related regions of the brain to form the distinction between self and other mental states and to create a comprehensive understanding of those mental states so that we may recognize, understand, and predict behavior. In general the theory of mind process is mediated by the dopaminergic-serotonergic system, which involves the TPJ as well as other associative regions necessary for mentalizing. Recent studies suggest that both the left TPJ, working in conjunction with the frontal cortex, and the right TPJ are involved in the representation of mental states; furthermore they suggest that the TPJ is particularly active in making the distinction between the mental states of self and others. A study in Nature Neuroscience from 2004 describes how the TPJ is involved in processing socially relevant cues including gaze direction and goal-directed action and also explains that results from the study show that lesions to this area of the brain result in an impaired ability to detect another persons belief. Moreover, studies have reported an increase in activity in the TPJ when patients are absorbing information through reading or images regarding other peoples' beliefs but not while observing information about physical control stimuli. Some studies, however, have shown that the TPJ, along with the cingulate cortex, is more specifically involved with attributing beliefs, but the process of mentalizing more generally is associated more with the medial prefrontal cortex. Another study in Current Biology from 2012 identifies the importance of the TPJ in both low-level, such as simple discrimination, and high-level, such as the ability to empathize, sociocognitive operations. In July 2011, a review from Neuropsychologia presented a model of the mentalizing network that established that mental states are first detected in the TPJ. The TPJ is composed of two discrete anatomical regions, the inferior parietal lobule (IPL) and the caudal parts of the superior temporal sulcus (pSTS), and both are active in the process of distinction between mental states of different individuals; thus, it is probable that this detection is the outcome of the combination and coordination of these two parts. Additionally, the right TPJ is involved in the ventral attention stream and contributes to the ability to focus attention on a particular stimuli or objective. It has also been observed that the interaction and communication between the dorsal and ventral streams involves the TPJ.

Out-of-body experiences

The TPJ is also a crucial structure for self-processing. Several neuro-imaging studies have shown an activation of the TPJ during different aspects of self-processing such as visuo-spatial perspective, self-other distinction, mental own body imagery, and vestibular and multi sensory integration. Damage in the TPJ has been linked to out-of-body experiences (OBEs), the feeling that one’s self is located outside one’s physical body.

An OBE is defined by the presence of three characteristics: disembodiment, the impression of seeing the world from a distant and elevated visuo-spatial perspective, and the impression of seeing one’s own body from this elevated perspective. OBEs mostly occur to people with epilepsy or migraines, but approximately 10% of the healthy population also experience OBEs once or twice in a lifetime. They usually occur spontaneously and are of short duration, making OBEs hard to study. Here is an example of a patient describing what he or she experienced during an OBE:

I was in bed and about to fall asleep when I had the distinct impression that “I” was at the ceiling level looking down at my body in the bed. I was very startled and frightened; immediately [afterward] I felt that, I was consciously back in the bed again.

It is suggested that OBEs are caused by multi-sensory disintegration in the TPJ disrupting different aspects of self-processing such as illusory reduplication, illusory self-location, and illusory perspective. The brain integrates different sensory inputs to create a representation of one’s body and its location in its surrounding. Some inhibition of discrepant inputs is required to have coherency, but in some cases, those discrepant inputs are so strong and come from more than one sensory source that it leads to two different representations of one’s own body. This multi-sensory disintegration at the TPJ leads to OBEs. An electromagnetic stimulation to the right TPJ of an patient with epilepsy induced an OBE. The author also states that these experiences are closely related to schizophrenia and phantom limb.

Temporal order judgement

Temporal order is the arrangement of events in time. By judging this, one can understand how we process things. Temporal order judgments require an individual to determine the relative timing between two spatially separate events. One study revealed that subjects had to determine the order of appearance of two objects as well as which object fit a certain property better. What was learned from this study was that when identifying the order or appearance, fMRI studies showed that there was bilateral activation of the TPJ. Meanwhile, when it comes to object characterization based on a property, it was noticed that there was only activation of the lTPJ. As such, it is evident that TPJ is involved in the “when” pathway of the brain.

Morality

Morality is the differentiation in intention between choosing between what is good and what is bad. Connections made at the TPJ help an individual understand their emotions and make decisions based on them. The TPJ allows the association of emotions to events or individuals, aiding in the decision making process. However, errors in this emotional processing can arise when patients have lesions in the TPJ or when the brain is electrically stimulated. transcranial magnetic stimulation (TMS) can be used to disrupt neural activity in the rTPJ right before a patient had to make a moral decision as well as during the decision making process, constituting to two different testing environments. Then, when presented with a moral dilemma, patients’ ability to make morally-sound decisions was deterred. TMS to the rTJ affects the ability of an individual to use mental states to make moral decisions. Studies also show that there is a relation between theory of mind and moral judgment, once again signifying the role of the rTPJ in morality.

Ventromedial prefrontal cortex

From Wikipedia, the free encyclopedia

Ventromedial prefrontal cortex
Ventromedial prefrontal cortex shown on medial and ventral views of the brain, reflecting approximate location of damage in patients with decision making deficits.
Medial surface of the brain with Brodmann's areas numbered.
Details
Identifiers
Latin	Cortex praefrontalis ventromedialis
Anatomical terms of neuroanatomy

The ventromedial prefrontal cortex (vmPFC) is a part of the prefrontal cortex in the mammalian brain. The ventral medial prefrontal is located in the frontal lobe at the bottom of the cerebral hemispheres and is implicated in the processing of risk and fear. It also plays a role in the inhibition of emotional responses, and in the process of decision making and self control. It is also involved in the cognitive evaluation of morality.

Anatomy

While the ventromedial prefrontal cortex does not have a universally agreed on demarcation, in most sources, it is equivalent to the ventromedial reward network of Ongur and Price. This network includes Brodmann area 10, Brodmann area 14, Brodmann area 25, and Brodmann area 32, as well as portions of Brodmann area 11, Brodmann area 12, and Brodmann area 13. However, not all sources agree on the boundaries of the area. Different researchers use the term ventromedial prefrontal cortex differently. Sometimes, the term is saved for the area above the medial orbitofrontal cortex, while at other times, 'ventromedial prefrontal cortex' is used to describe a broad area in the lower (ventral) central (medial) region of the prefrontal cortex, of which the medial orbitofrontal cortex constitutes the lowermost part. This latter, broader area, corresponds to the area damaged in patients with decision-making impairments investigated by António Damásio and colleagues (see diagram, and below).

To get a rough idea of where the ventromedial prefrontal cortex is, recall that the left and right hemispheres of the brain are separated [by the longitudinal cerebral fissure]. Now imagine you could take your hand and starting at the anterior brain (where your forehead is) insert it into this gap until you reached the insula (a structure that is beneath the frontal lobe). Your palm would be touching a part of the prefrontal cortex, which is in the front part of the brain and the lower part of your palm would be touching the ventral medial prefrontal cortex.

The ventromedial prefrontal cortex is connected to and receives input from the ventral tegmental area, amygdala, the temporal lobe, the olfactory system, and the dorsomedial thalamus. It, in turn, sends signals to many different brain regions including; The temporal lobe, amygdala, the lateral hypothalamus, the hippocampal formation, the cingulate cortex, and certain other regions of the prefrontal cortex.^[4] This huge network of connections affords the vmPFC the ability to receive and monitor large amounts of sensory data and to affect and influence a plethora of other brain regions, particularly the amygdala.

Function

Functional differences between the orbitofrontal and ventromedial areas of the pre-frontal cortex have not yet been clearly established, although the areas of the ventromedial cortex superior to the orbitofrontal cortex are much less associated with social functions and more with pure emotion regulation. Research in developmental neuroscience also suggested that neural networks in the ventromedial prefrontal cortex are rapidly developing during adolescence and young adulthood supporting emotion regulation through the amygdala, being associated with a decrease in cortisol levels.

There are only a few reports of people with early-onset vmPFC damage during childhood, but these individuals tend to have severe antisocial behavior and impaired moral judgment. Compared to individuals with damage later in life, their behavior pattern is similar but more severe.

Decision making

Patients with bilateral lesions of the vmPFC develop severe impairments in personal and social decision-making even though most of their intellectual ability is preserved. For instance, they have difficulties in choosing between options with uncertain outcomes, whether the uncertainty is in the form of a risk or of an ambiguity. After their lesion, these patients have an impaired capacity to learn from their mistakes, making the same decisions again and again even though they lead to negative consequences. These patients choose alternatives that give immediate rewards, but seem to be blind to the future consequences of their actions. However, the underlying mechanisms of this behaviour are not yet fully understood.

Damage to the ventromedial prefrontal cortex (especially in the right hemisphere) has been connected with deficits in detecting irony, sarcasm, and deception. Subjects with damage in this area have been found to be more easily influenced by misleading advertising. This has been attributed to a disruption of a "false tagging mechanism" which provides doubt and skepticism of new beliefs.

People with damage to the ventromedial prefrontal cortex still retain the ability to consciously make moral judgments without error, but only in hypothetical situations presented to them. There is a gap in reasoning when applying the same moral principles to similar situations in their own lives. The result is that people make decisions that are inconsistent with their self professed moral values. People with early damage to the ventromedial prefrontal cortex are more likely to endorse self-serving actions that break moral rules or cause harm to others. This is especially true for patients whose damage occurred the earliest in life.

Emotions and an understanding of social norms are used to provide reasoning of the moral nature on our behaviors, beliefs, and the people around us. The vmPFC works as the neural basis in allowing emotion to influence moral judgement. The trolley dilemma is a classic situation testing emotional involvement in moral judgment. In the trolley dilemma, participants imagine a runaway trolley heading toward five people who will be killed if the trolley is to continue. The participant is to decide whether to allow the trolley to run its course, or to shunt the trolley off to another track where it will only kill one person. Most people choose to throw the switch, concluding that it is moral to save five by sacrificing the life of one. In a variation, there is no switch at hand to shunt the trolley, instead the participant has the option to push someone on the trolley tracks to stop it from moving. Most people are repulsed at the idea of pushing the man to his death, even though outcome is the same as the first dilemma, with five people surviving and one person dying. The more personal nature of pushing someone onto the tracks discourages this response, and the role of emotion is proposed to be the difference in the reasoning. In functional imaging studies, increased activity in the vmPFC is associated with thinking of these personal moral situations, while making harmless decisions does not. Patients with vmPFC lesions made the same decision in impersonal and personal dilemmas. Dysfunction of the vmPFC causes failure in using correct moral emotion, which explains why these patients showed less emotional responses when facing these dilemmas.

Regulation of emotion

The vmPFC plays an important role in regulating and inhibiting our response to emotions. VmPFC seems to use our emotional reactions to model our behavior and control emotional reactions in certain social situations. The inputs of the vmPFC provide it with information from the environment and the plans of the frontal lobe, and its outputs allow the vmPFC to control different physiological responses and behaviors. The role of the vmPFC is especially highlighted in people with damage to this region. A damaged vmPFC causes impairments of behavioral control and decision making, consequences which are rooted in emotional dysregulation. The first and most famous case of someone with defects to this region was Phineas Gage, a railroad construction foreman who had his vmPFC bilaterally destroyed in an accident in 1848. Before his accident, Gage was described as “serious, industrious and energetic. Afterward he became childish, irresponsible, and thoughtless of others.” Another patient with vmPFC damage wasted away his life savings on foolish investments and failed to make appropriate decisions in his personal life. In patients with vmPFC damage, evidence shows that there is a correlation between emotional dysregulation and dysfunction in real world competencies.

The amygdala plays a significant role in instigating the emotional reactions associated with anger and violence. With the vmPFC’s outputs to the amygdala, the vmPFC plays a part in preventing such behavior. Evidence has shown that impulsive murderers have decreased activity in the prefrontal cortex and increased activity in subcortical areas such as the amygdala. This imbalance can enhance actions that are created by negative emotions and limit the ability of the prefrontal cortex to control these emotions. Lower activation in the prefrontal cortex is also correlated with antisocial behavior. The dysfunction of the ventromedial cortex seems to, in part, be caused by lower levels of serotonin release.

The vmPFC also is involved in courage. In experiments with participants allowing snakes to come near or away from them, acts of courage correlated with activation in the vmPFC, specifically the subgenual anterior cingulate cortex.

Activation of the vmPFC is associated with successful suppression of emotional responses to a negative emotional signal. Patients with vmPFC lesions show defects both in emotional response and emotion regulation. Their emotional responsivity is generally diminished and they show markedly reduced social emotions such as compassion, shame and guilt. These are emotions that are closely associated with moral values. Patients also exhibit poorly regulated anger and frustration tolerance in certain circumstances.

Patients with focal lesions in the vmPFC show personality changes such as lack of empathy, irresponsibility, and poor decision making. These traits are similar to psychopathic personality traits. In addition, a correlation between individuals with a history of physical violence and decreased grey matter density in the vmPFC has been evidenced.

The right half of the ventromedial prefrontal cortex was associated with regulating the interaction of cognition and affect in the production of empathic responses. Hedonic (pleasure) responses were also associations to orbitofrontal cortex activity level by Morten Kringelbach. This finding contributes findings suggesting ventromedial prefrontal cortex being associated with preference judgement, possibly assigning the ventromedial prefrontal cortex a key role in constructing one's self. Studies with Posttraumatic Stress Disorder (PTSD) also supported the idea that the ventromedial prefrontal cortex is an important component for reactivating past emotional associations and events, therefore essentially mediating pathogenesis of PTSD. Dysfunction of the vmPFC has also been identified as playing a role in PTSD-affected parents' response to their own children's mental states. Treatments geared to the activation of the ventromedial prefrontal cortex were therefore suggested for individuals and parent-child relationships affected by PTSD. The right half of the ventrolateral prefrontal cortex, being active during emotion regulation, was activated when participants were offered an unfair offer in a scenario. Specific deficits in reversal learning and decision-making have led to the hypothesis that the ventromedial prefrontal cortex is a major locus of dysfunction in the mild stages of the behavioural variant of frontotemporal dementia.

The capacity for mature defense mechanisms such as intellectualization, compensation, reaction formation, and isolation has been tied to proper functioning of the right ventromedial prefrontal cortex, while more primitive defense mechanisms such as projection, splitting, verbal denial, and fantasy have been found to rely on other regions, primarily in the left hemisphere .

Somatic marker hypothesis

One particularly notable theory of vmPFC function is the somatic marker hypothesis, accredited to António Damásio. By this hypothesis, the vmPFC has a central role in adapting somatic markers—emotional associations, or associations between mental objects and visceral (bodily) feedback—for use in natural decision making. This account also gives the vmPFC a role in moderating emotions and emotional reactions because whether the vmPFC decides the markers are positive or negative affects the appropriate response in a particular situation. However, a critical review of this hypothesis concluded that there is a need for additional empirical data to support the somatic marker theory.

Extinction

Another role that the vmPFC plays is in the process of extinction, the gradual weakening and eventual cessation of a conditioned response, as studies have shown increased activation of the vmPFC after extinction training. The specific role played by the vmPFC concerning extinction is not well understood, but it is believed that it plays a necessary role in the recall of extinction learning after a long period of time. Studies show that it aids in the consolidation of extinction learning. A separate study has implicated the correlation between the cortical thickness of the vmPFC and the degree of extinction memory. Patients with larger vmPFCs tended to have lower responses to the extinct conditioned stimulus, therefore suggesting a superior extinction memory. In general, the ventromedial prefrontal cortex plays a major role in the later stages of memory consolidation.

Gender specific social cues

Ventromedial prefrontal cortex lesions were also associated with a deficit in processing gender specific social cues. One experiment tested the ability of patients with vmPFC lesions to categorize gender-specific names, attributes, and attitudes compared to patients with dorsolateral prefrontal cortex lesions and control subjects. Whereas the patients with dorsolateral prefrontal cortex lesions performed similarly to the control subjects on tests indicating gender stereotypes, patients with ventromedial prefrontal cortex lesions demonstrated impaired stereotypic social knowledge.

Cocaine abuse

Frequent cocaine users have been shown to have lower than normal activity in the ventromedial prefrontal cortex. When asked to perform certain tasks that rely heavily on activation of this area of the brain, the cocaine users perform worse and have less prefrontal cortex activation than the control subjects. The quantity of cocaine used was found to be inversely proportional to the level of activation.

The prefrontal cortex is also physically affected by cocaine use. Chronic use has been shown to lead to a decrease in the amount of gray matter in the ventromedial prefrontal cortex. The decrease in gray matter and effect on behavior is analogous to a person having lesions throughout their medial prefrontal cortex. Specifically, the pyramidal cells of the ventromedial prefrontal cortex are known to be linked with drug seeking behaviors. Both an increased and decreased level of activity in these pyramidal cells has shown to lead to extinction of cocaine-seeking behaviors depending on when the activation takes place. Inactivation of these cells was needed to inhibit cocaine-seeking behavior after a longer duration of time, whereas activation was required to reduce the behavior soon after using cocaine.