Near-death experience
[9][10] In 1892, a series of subjective observations by workers falling from scaffolds, soldiers who suffered injuries, climbers who had fallen from heights and other individuals who had come close to death such as in near drownings and accidents was reported by Albert Heim.
[6] Bruce Greyson argues that the general features of the experience include impressions of being outside one's physical body, visions of deceased relatives and religious figures, and transcendence of egotic and spatiotemporal boundaries.
[18][19] Common traits that have been reported by NDErs are: Note that an OBE may be part of an NDE, but can happen in instances other than when a person is about to die, such as fainting, deep sleep, and alcohol or drug use.
[31] Bruce Greyson found that NDEs had a lack of precision in diagnosis, so he created a questionnaire for those who had experienced NDE composed of 80 characteristics to study common effects, mechanisms, sensations and reactions.
Long set out to discover the "reality" of NDEs mostly linked to cardiac arrest patients by using this scale and reviewing Near Death Experience Research Foundation studies.
[34] His first line of evidence shows that 835 out of 1,122 people who had experienced NDE seemed to feel an increase in alertness and consciousness although studies proved no sign of electrical brain activity.
[40] The oldest known medical report of near-death experiences was written by Pierre-Jean du Monchaux, an 18th-century French military doctor who described such a case in his book Anecdotes de Médecine.
[46] Researchers from the University of Michigan led by Jimo Borjigin discovered that areas of the brain responsible for interior visual experience were more active during cardiac arrest.
According to the study, a sudden surge in brain activity at the time of cardiac arrest may be what causes people to perceive a bright white light when having a near-death experience.
Intriguingly, the long-range gamma connectivity between the posterior hot zones and the prefrontal areas at near-death was significantly higher over baseline only for those crossing the midline.
Studies suggest that interhemispheric circuitry is important for memory recall, and gamma synchrony across the midlines is critical for learning, information integration, and perception.
Parnia and colleagues investigated out-of-body experience claims by placing figures in areas where patients were likely to be resuscitated on suspended boards facing the ceiling, not visible from the floor.
[49] In 2001, Pim van Lommel, a cardiologist from the Netherlands, and his team conducted a study on NDEs including 344 cardiac arrest patients who had been successfully resuscitated in 10 Dutch hospitals.
[52] One such test consisted of installing shelves, bearing a variety of images and facing the ceiling, hence not visible to hospital staff, in rooms where cardiac-arrest patients were more likely to occur.
[50] As of May 2016[update], a posting at the UK Clinical Trials Gateway website described plans for AWARE II, a two-year multicenter observational study of 900–1,500 patients experiencing cardiac arrest, which said that subject recruitment had started on 1 August 2014 and that the scheduled end date was 31 May 2017.
[57] A three-year longitudinal study has revealed that some Buddhist meditation practitioners are able to willfully induce near-death experiences at a pre-planned point in time.
[59] In a 2005 review article, psychologist Chris French[49] categorized models that try to explain NDEs into three broad groups which "are not distinct and independent, but instead show considerable overlap": spiritual (or transcendental), psychological, and physiological.
[11] A wide range of physiological theories of the NDE have been put forward, including those based upon cerebral hypoxia, anoxia, and hypercapnia; endorphins and other neurotransmitters; and abnormal activity in the temporal lobes.
[67] Among the researchers and commentators who tend to emphasize a naturalistic and neurological base for the experience is the British psychologist Susan Blackmore (1993), with her "dying brain hypothesis".
Neuroscientists Olaf Blanke and Sebastian Dieguez (2009),[69] from the Ecole Polytechnique Fédérale de Lausanne, Switzerland, propose a brain-based model with two types of NDEs: They suggest that damage to the bilateral occipital cortex may lead to visual features of NDEs such as seeing a tunnel or lights, and "damage to unilateral or bilateral temporal lobe structures such as the hippocampus and amygdala" may lead to emotional experiences, memory flashbacks or a life review.
They concluded that future neuroscientific studies are likely to reveal the neuroanatomical basis of the NDE, which will lead to the demystification of the subject without needing paranormal explanations.
[4] French has written that the "temporal lobe is almost certain to be involved in NDEs, given that both damage to and direct cortical stimulation of this area are known to produce a number of experiences corresponding to those of the NDE, including OBEs, hallucinations, and memory flashbacks".
[71][72] Likewise, Greyson[11] writes that although some, or any of the proposed neuroanatomical models may serve to explain NDEs and pathways through which they are expressed, they remain speculative at this stage, since they have not been tested in empirical studies.
[11] Some theories explain reported NDE experiences as resulting from drugs used during resuscitation (in the case of resuscitation-induced NDEs) ─ for example, ketamine ─ or from endogenous chemicals (neurotransmitters) that transmit signals between brain cells:[49] According to Parnia, neurochemical models are not backed by data.
[50] Parnia writes that no data has been collected via thorough and careful experimentation to back "a possible causal relationship or even an association" between neurochemical agents and NDE experiences.
"[49][82] However, acceleration-induced hypoxia's primary characteristics are "rhythmic jerking of the limbs, compromised memory of events just prior to the onset of unconsciousness, tingling of extremities ..." that are not observed during NDEs.
[18] Also, G-LOC episodes do not feature life reviews, mystical experiences and "long-lasting transformational aftereffects", although this may be due to the fact that subjects have no expectation of dying.
[83] According to Engmann (2008), near-death experiences of people who are clinically dead are psychopathological symptoms caused by a severe malfunction of the brain resulting from the cessation of cerebral blood circulation.
This basis could be congruent with the thesis of pathoclisis – the inclination of special parts of the brain to be the first to be damaged in case of disease, lack of oxygen, or malnutrition – established in 1922 by Cécile Vogt-Mugnier and Oskar Vogt.
[31] An NDE often involves vivid and complex mentation, sensation and memory-formation under circumstances of completely disabled brain function during general anesthesia, or near-complete cessation of cerebral blood flow and oxygen uptake during cardiac arrest.
