|Can such things be?|
|The Twilight Zone|
A near-death experience may refer to anything experienced by someone in clinical death, though usually refers to some kind of spiritual experience, such as an out-of-body experience, and is often cited as evidence for the existence of an afterlife by believers.
By the broadest definition, a near-death experience (NDE) can occur as a result of a coma, near-death accident, dreaming, drugs, stress, surgery, seizure, sudden oxygen deprivation, deathbed, brain stimulation, or orgasm. Around ten to 20 percent of people coming close to dying reported experiencing some form of NDE.
There are no "research diagnostic criteria" for NDE's as there are for other psychiatric disorders. Thus researchers are often in disagreement as to whether a collection of phenomena constitutes a NDE and also whether a single cause or multiple causes should be identified for a given experience.
Psychologist Raymond Moody coined the phrase "near-death experience" in Life After Life (1975) and established a composite experience based on testimonials. Experiences vary, and a typical NDE will include one or more elements.
Claimed experiencers of them have described NDEs as a transcendent mystical state. They reported sensing all-encompassing love, beauty, and peace, contentment, timelessness, and painlessness. Some perceived that they had access to unlimited knowledge. This knowledge cannot be reproduced suggesting the experience is illusory. Many explained that the experience was beyond words. In contrast, some have had frightening visions.
According to a study by Pim van Lommel and others, 50% of NDE'ers reported an awareness that they were dead. Many admitted that the NDE seemed "real," and although it is common to experience an extreme clarity of thought, still others reported feelings of disorientation.
According to van Lommel 31% of NDE'ers reported passing rapidly through a transitional world of dark tunnels in what is sometimes referred to as "the tunnel experience." Often they then emerged into a light at the end of the tunnel.
It is common for NDE'ers to report the perception of a presence that they believed to be God or some other spiritually neutral entity or to perceive God as light and to engage in telepathic communication with God or Christ. According to van Lommel 32% reported meeting with deceased persons, especially loved ones, with which telepathic communication might occur. NDE'ers have also seen images of (usually) helpful people, landscapes, religious or mythical figures (such as angels), celebrities, or fictional characters. According to a study by Peter and Elizabeth Fenwick, 14% of NDE'ers reported encountering living persons. Some recalled hearing specific sounds.
A NDE may include a "life review," or the emergence of memories into consciousness, apparently in order to be relived or judged. According to the Fenwicks, 15% of NDE's included recalled memories, although only half of memories were deemed to be significant.
Some NDE'ers recalled a desire not to leave their body and making the decision to return to it. According to van Lommel 8% reported a threshold crossing or "point of no return" beyond which they felt they would be unable to return to life. However, some crossed this threshold and managed to return anyway. Additionally a portion of NDE'ers reported feeling a detachment from the body or even seeing their physical body during an out-of-body experience (OBE).
Finally, a significant number of NDE'ers indicated that the experience had a life-changing effect on them. Additionally there have been reports that NDE'ers have problems making watches stop, look younger, and gain psychic abilities, healing powers, or prophetic visions afterward, although none of these effects has been substantiated.
 Scientific explanation
The relative similarities of NDE accounts imply a biological origin. Viewed as a scientific phenomenon, the NDE is of some interest to medicine and psychiatry. Hypotheses advanced by researchers include neurochemical as well as psychological explanations. Obviously the calming effects of NDEs would have physical as well as emotional benefits to an individual who was close to dying.
Aspects of NDEs indicate that the temporal lobe is involved. The temporoparietal lobe is the area in which the brain locates itself in space - that is, behind the eyes. Co-ordination between the organs necessary for interaction with the outside world - limbs, sensory organs and of course the brain - is vital for our survival, and the brain must locate the body's organs (mistakes in doing this could be the cause of phantom and alien limb syndromes) and itself in order for this to work. Electrical stimulation of the temporoparietal lobe has been shown to reliably induce the same dissociation found in NDEs and OBEs. Out-of-body experiences can also occur during episodes of fainting or extreme physical exhaustion such as hiking at high altitude. Additionally, some of the elements of NDEs can be reproduced with anesthetics. Kevin Nelson suggests that the common factor in all these experiences is reduced oxygen supply to the brain, which shuts down region by region in such circumstances to conserve energy. When the oxygen supply to the temporoparietal lobe is cut off, this would trigger an out-of-body experience.
NDEers have been associated with a rather specific psychological profile including sleep/dream patterns and positive coping styles. The tendency for individuals to experience OBEs can be predicted by somatoform dissociation, the failure to process somatic experiences. The astronomer Carl Sagan suggested that common NDE elements such as tunneling, light, and telepathic communion with a god may be a reactivation of birth memories, but the brains of fetuses and newborn babies lack the synapses for memory formation, making this notion poetic but unscientific.
Some elements of NDEs may represent the incorporation of stimuli sensed subconsciously, for example via "anesthesia awareness" during surgery. The ability to later describe events taking place during an OBE may be the result of easy guesses or leading questions or unintentional information given by the interviewer. Keith Augustine quotes Dr. Susan Blackmore that "'prior knowledge, fantasy and lucky guesses and the remaining operating senses of hearing and touch,' plus 'the way memory works to recall accurate items and forget the wrong ones' is sufficient to explain out-of-body imagery in NDEs."
Testimonials may reflect what one has heard or expects based on the testimonials of others. In addition, NDE research likely suffers from the "file-drawer problem," cherry picking only those testimonials that help advance the researcher's hypothesis.
P Z Myers suggests that false memories may be generated as the brain tries to make sense of a time when consciousness did not exist.  Further wishful thinking may generate experiences confirming what a subject wants to believe and brain damage may prevent a subject recognising that the experience was a dream. 
It should be noted that, due to the complexity of NDEs, a particular scientific hypothesis of their cause need not explain all possible experiences.
Other notable explanations include that NDEs are the result of telepathic communication from medical staff or that they are a trick of Satan.
Based on his research, Dr. Karl Jansen notes that "Recent advances in neuroscience are bringing us closer to a brain-based understanding of the NDE as an altered state of consciousness." Jansen also determined that the effects of an NDE can be induced with ketamine, a hallucinogenic, dissociative anesthetic related to PCP. Jansen explains, "Ketamine administered by intravenous injection is capable of reproducing all of the features of the NDE which have been commonly described."
Regarding ketamine, Jansen quotes Doctors Grinspoon and Bakalar that "The dissociative experiences often seem so genuine that users are not sure that they have not actually left their bodies." Jansen quotes Dr. Leary that ketamine use represents "experiments in voluntary death."
Jansen's explanation of why ketamine and a near-death condition will cause similar effects is summarized as follows:
NMDA receptors in portions of the brain are important in cognitive processing and other functions. The same region of the brain plays a role in epileptic events and others in which cell (neuron) damage may occur due to the presence of glutamate (neurotransmitters). The use of ketamine prevents such damage. The brain might possibly release a neuroprotective counter-flood to glutamate similar to ketamine during catastrophic events. It is known, for example, that endopsychosins and magnesium and zinc ions naturally bind to the same (drug binding) sites as ketamine (the PCP receptor of the NMDA receptor). The hallucinogenic effects of ketamine are due to an NMDA receptor blockade.
Thus Jansen concludes "Near-death experiences (NDEs) can be reproduced by ketamine via blockade of receptors in the brain (the N-methyl-D-aspartate, NMDA receptors) for the neurotransmitter glutamate." Most of this explanation is based on well-understood observations of neurological processes.
When a NDE is induced by ketamine administered by an anesthetist, it is known as "emergence phenomena" or "psychic emergence reaction."
Like NDEs, ketamine use has therapeutic after-effects.
 Evidence of afterlife
NDE's and especially OBE's are cited as evidence of disembodied spirits, separate consciousness, and, therefore, life after death. Proponents claim the consistency of testimonials and the life-changing effects indicate that NDE's are real.
Additionally subjects' testimonials of clarity of thought is presented as evidence of the reality of NDE's. However, consider Jansen's finding that "...30% of normal subjects given ketamine were certain that they had not been dreaming or hallucinating, but that the events had really happened." By its definition a hallucination seems real. In fact drunk drivers commonly admit perceiving clarity of thought. Jansen asserts, "A personal conviction of the 'reality' of an NDE does not invalidate scientific explanations."
The explanation that NDE's are in fact passage into the afterlife presents several contradictions. Jansen quotes Dr. Melvin Morse that "One of the many contradictions which 'after-lifers' can not resolve is that 'the spirit rises out of the body leaving the brain behind, but somehow still incorporating neuronal functions such as sight, hearing, and proprioception.'" Such a separation of the "spirit" and the brain ignores scientific evidence that indicates consciousness is dependent on the brain.
Also consider that at times living persons are encountered in NDE's. If NDE's were real then expecting to see living persons there would be as reasonable as expecting the persons one sees in dreams to actually be there.
Religious figures encountered in NDE's appear as they are commonly depicted, although trends vary by culture. In other words one sees exactly what one expects to see. Additionally historical accounts differ from the typical Western NDE.
There are discrepancies documented in patient descriptions compared to actual events during OBE's. Additionally experiments designed to confirm OBE's have all ended in failure.
It appears that the theme of a threshold occurs in NDE's because subjects are seeking a rationale as to why they were sent back from the afterlife. However, sometimes the choice is made to cross the threshold, and yet the NDE'er returns to the living world nonetheless.
Finally it is not clear why only a percentage of subjects coming close to dying report having NDE's.
Afterlife proponents point out that NDE's occur during a period of no measurable brain activity. However, this excludes the possibility of the experience occurring during immeasurable brain activity or, more likely, upon waking. In fact the observation that the experience was remembered implies that the brain was working at the time.
Proponents also claim the observation that blind people see images during NDE's is evidence of their reality. However, it may be that blind people see what they expect to see.
Rene Jorgensen, who concludes through the evidence of testimonials that NDE's are evidence of an afterlife, admits that "...people who have been brought back from the other side are the most reliable sources of information about life after death." Thus the evidence is anecdotal.
Note that logically anyone who is resuscitated did not actually die, and their experiences cannot be taken as evidence of an afterlife. Even some proponents agree that NDE's do not represent evidence of an afterlife. Similarly, a brain-based explanation of NDE need not be taken as evidence against life after death, although this argument is fairly devoid of usefulness.
- ↑ van Lommel, Pim; van Wees, Ruud; Meyers, Vincent; Elfferich, Ingrid. "Near-death experience in survivors of cardiac arrest: a prospective study in the Netherlands."
- ↑ Augustine, Keith (2003). "Hallucinatory Near-Death Experiences."
- ↑ Augustine, Keith (2003). "Hallucinatory Near-Death Experiences."
- ↑ Nelson, Kevin. The God Impulse (London: Simon & Schuster, 2011)
- ↑ Nelson, p.121
- ↑ Blackmore, Susan. Dying to Live: Near-Death Experiences. Buffalo, NY: Prometheus Books, 1993. (quoted by Augustine, Keith (2003/2008). "Hallucinatory Near-Death Experiences (2003)." Infidels.)
- ↑ Near-death, distorted
- ↑ Newsweek panders to the deluded again
- ↑ Jansen, Karl L. R. "Using Ketamine to Induce the Near-Death Experience." Lycaeum. 9/17/00.
- ↑ Grinspoon, L. and Bakalar, S. B. (1981). Psychedelic Drugs Reconsidered. Basic Books, New York. (quoted by Karl L. R. Jansen)
- ↑ Leary, T. F. (1983) Flashbacks, an autobiography. J. P. Tarcher, L. A., p375. (quoted by Karl L. R. Jansen)
- ↑ Jansen, Karl L. R. "The Ketamine Model of the Near Death Experience: A Central Role for the NMDA Receptor." Lycaeum. 9/17/00.
- ↑ Morse, M. L. (1989). Comments on 'A neurobiological model for near-death experiences'. Journal of Near-Death Studies, 7, 223-228 (quoted by Karl L. R. Jansen)
- ↑ Rene Jorgensen
- Near-Death Experiences and the Afterlife
- Near Death Experience Research Foundation
- Augustine, Keith (2003/2008). "Hallucinatory Near-Death Experiences (2003)." Infidels.
- Near-Death Experiences and the Brain by Chris French
- "Near-death experience (NDE)." The Skeptic's Dictionary.
- Life After Death, The Near Death Experience
- Hudetz, J. A., et. al. (4/28/09). "Ketamine attenuates post-operative cognitive dysfunction after cardiac surgery." PubMed.gov.
- Think about Near Death Experiences More on ketamine
- Culture, biology, and the near-death experience. A reappraisal.
- I've had my own near-death experience. Here P Z Meyers compares his real near death experience with a fantasy by Ray Comfort