None of the materialist attempts to explain NDEs can really explain them. NDEs cannot be explained by: a lack of oxygen, a dying brain, hallucinations, religious expectations, cultural expectations, hearing about medical procedures after the fact, hearing during resuscitation, brain dysfunction, inhibitory network failure, retinal dysfunction causing an image of a tunnel, brain chemicals such as ketamine, endogenous opioids, neurotransmitter imbalances, or hallucinogens including DMT, REM intrusions, epilepsy or seizures, psychopathology, unique personality traits, residual brain activity during unconsciousness, the experience occurring before or after brain activity stopped, brain activity during CPR, evolutionary adaptation, depersonalization, memory of birth, medication, naloxone, defense against dying, partial anesthesia, misuse of anecdotes, or selective reporting.
http://ncu9nc.blogspot.com/2013/07/materialist-explanations-of-ndes-fail.html#nde_explain_oxygen
Lack of oxygen:
- Hogan: Lack of oxygen causes stupor without memories of the experience. People experiencing NDEs report enhanced consciousness not stupor and they remember their NDE. "Dr. Fred Schoonmaker, a cardiologist from Denver, had by 1979 carried out investigations of over 2,000 patients who had suffered cardiac arrests, many of whom reported NDEs. His findings showed that NDEs occurred when there was no deprivation of oxygen."
- Tymn (Summary of Hogan)
- Prescott (including acceleration induced hypoxia in pilots training under high g forces.):
The primary features of acceleration-induced hypoxia, however, are myoclonic convulsions (rhythmic jerking of the limbs), impaired memory for events just prior to the onset of unconsciousness, tingling in the extremities and around the mouth, confusion and disorientation upon awakening, and paralysis, symptoms that do not occur in association with NDEs. Moreover, contrary to NDEs, the visual images Whinnery reported frequently included living people, but never deceased people; and no life review or accurate out-of-body perceptions have been reported in acceleration-induced loss of consciousness.
- Facco and Christian
Evidence against simple mechanistic interpretations comes also from a well-known prospective study by van Lommel et al. (2001), which showed no influence of given medication even in patients who were in coma for weeks. Factors such as duration of cardiac arrest (the degree of anoxia), duration of unconsciousness, intubation, induced cardiac arrest, and the administered medication were found to be irrelevant in the occurrence of NDEs.
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Furthermore, complete brain anoxia with absent electrical activity in cardiac arrest is incompatible with any form of consciousness, according to present scientific knowledge, making the finding of an explanation for NDEs a challenging task for the ruling physicalist and reductionist view of biomedicine (Kelly et al., 2007; Greyson, 2010b; van Lommel, 2010).
- Beauregard:
As pointed out by renowned NDE researcher Sam Parnia, some individuals have reported an NDE when they had not been terminally ill and so would have had normal levels of oxygen in their brains.
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Parnia raises another problem: When oxygen levels decrease markedly, patients whose lungs or hearts do not work properly experience an “acute confusional state,” during which they are highly confused and agitated and have little or no memory recall. In stark contrast, during NDEs people experience lucid consciousness, well-structured thought processes, and clear reasoning. They also have an excellent memory of the NDE, which usually stays with them for several decades.
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Such rapid acceleration decreases blood flow and, consequently, delivery of oxygen to the brain. In so doing, it induces brief periods of unconsciousness that Whinnery calls “dreamlets.” Whinnery hypothesized that although some of the core features of NDEs are found during dreamlets, the main characteristics of dreamlets are impaired memory for events just prior to the onset of unconsciousness, confusion, and disorientation upon awakening. These symptoms are not typically associated with NDEs. In addition, life transformations are never reported following dreamlets.
- Greyson
Moreover, cells in the hippocampus, the region thought to be essential for memory formation, are especially vulnerable to the effects of anoxia (Vriens et al., 1996).
Fighter pilots experienceing anoxia due to high g forces tend to report visions of living people not deceased people as NDErs do.
- near-death.com
Other possible explanations are a lack of oxygen in the brain, or too much carbon dioxide. But these would not explain why some patients are able to give full and cogent reports of things that went on around them during their NDE. Cardiologist Dr. Michael Sabom has reported one patient who, while having a NDE, watched his doctor perform a blood test that revealed both high oxygen and low carbon dioxide. Comparisons between NDEs and hallucinations produced by an oxygen-starved brain show that the latter are chaotic and much more similar to psychotic hallucinations. Confusion, disorientation, and fear are the typical characteristics, compared with the tranquility, calm, and sense of order of a NDE. There are some features in common: a sense of well-being and power, and themes of death and dying. But people who have experienced both at different times say that there is an unmistakable difference.
Hallucinations, whether deliberately drug-induced, the result of medication, or caused by oxygen deprivation, almost always take place while the subject is awake and conscious, whereas NDEs happen during unconsciousness, sometimes when the subject is so close to death that no record of brain activity is recorded on an electroencephalograph, the machine that monitors brain waves. Also, the medical conditions that take subjects to the brink of death, and to having a NDE, do not necessarily include oxygen-deprivation, or any medication. This is particularly true of accident victims. NDEs appear to occur at the moment when the threat of death occurs, not necessarily at the time, maybe hours later, when death is close enough to be starving the brain of oxygen.
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Ultimately, all materialistic explanations for NDEs must fail because they cannot explain the paranormal components of the phenomena, such as shared near-death experiences where multiple people share a near-death experience, and veridical near-death experiences where the experiencer remembers verifiable information that could not have been perceived with his normal senses even if he were conscious.