Life in B Flat(Science and Spirituality): Materialist explanations of NDEs fail to explain the phenomenon.

There are many anomalies associated with near-death experiences. None of the materialist attempts to provide physiological explanations for these anomalies can actually explain the phenomenon. Below is a list of on-line references that refute materialist explanations of near-death experiences. Also, at the bottom are links to refutations of Susan Blackmore, and Caroline Watt.

Introduction
Sources
List of Materialist Hypotheses Refuted
Summary of Refutations
Detailed list of hypotheses refuted by each source
Related Links

Introduction

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. I have discussed these types of cases and provided examples on my website and elsewhere on this blog. Even claims that veridical perceptions are due to ESP do not contradict the conclusion that near-death experiences represent out-of-the-body consciousness and evidence for the afterlife because ESP is not produced by the brain and ESP during near-death experiences is best explained as out-of-the-body consciousness. However it is interesting to see how weak the materialists hypotheses are on their own ground. It shows that these materialistic hypotheses are proposed by people who are incredibly ignorant of near-death experiences. It says something sad about the current state of the scientific profession that scientists would make such reckless proposals without investigating the subject they are discussing.

Sources

Chapter 2 in "Your Eternal Self by R. Craig Hogan, Ph.D.
Debunking the NDE Debunkers by Michael Tymn (Summary of the above chapter.)
Irreducible Mind and the NDE Michael Prescott discusses chapter 6 of the book "Irreducible Mind" by Edward F. Kelly, Emily Williams Kelly, et al.
Near-death experiences between science and prejudice by Enrico Facco and Christian. (2012) Frontiers in Human Neuroscience. 6:209. doi: 10.3389/fnhum.2012.00209
Near death, explained Near death, explained By Mario Beauregard at Salon.com, Saturday, Apr 21, 2012
Cosmological Implications of Near-Death Experiences by Bruce Greyson, Journal of Cosmology, 2011, Vol. 14.
Scientific theories of the near-death experience at near-death.com
Dr. Jeffrey Long Takes On Critics of, Evidence of the Afterlife at skeptiko.com
Proof of Heaven, Appendix B by Eben Alexander

List of Materialist Hypotheses Refuted:

Click on the hypothesis to see the refutation below, click on the sources to go to the original articles.

Lack of oxygen: Hogan, Tymn, Prescott (including acceleration induced hypoxia in pilots training under high g forces.), Facco and Christian, Beauregard, Greyson, near-death.com
Dying Brain: Hogan, Tymn, Beauregard, Greyson, near-death.com
Hallucinations: Hogan, near-death.com, Long
Religious Expectations: Hogan, Tymn, Long
Cultural Expectations: Hogan, Tymn, Long
Hearing about medical procedures after the fact: Hogan, Tymn
Hearing during resuscitation: Hogan, Prescott, Long
Brain Dysfunction (such as temporal lobe dysfunction): Tymn, Prescott, Facco and Christian, Beauregard, Greyson, near-death.com, Alexander
Inhibitory Network Failure Alexander
Retinal dysfunction causing an image of the tunnel: Facco and Christian
Visual cortex dysinhibition associated with anoxia causing an image of the tunnel: Facco and Christian
Brain chemicals such as ketamine, DMT, etc.: Prescott (ketamine), Facco and Christian (endogenous opioids, neurotransmitter imbalance and hallucinogens including DMT), Beauregard (ketamine), Long, Alexander
REM Intrusions: Facco and Christian, Long
Epilepsy or seizures: Beauregard
Psychopathology: Hogan, Tymn, Greyson
Unique Personality Traits: Greyson
Residual brain activity during unconsciousness: Greyson, Alexander
The experience occurred before or after brain activity stopped: Greyson
The experience occurred during CPR: Long
Evolutionary Adaptation: near-death.com, Alexander
Depersonalization: Hogan, near-death.com
Memory of birth: near-death.com
Medication: Hogan, Tymn, Facco and Christian
Defense against dying: Tymn
Partial anesthesia: Prescott, Long
Misuse of anecdotes: Long
Selective reporting: Long

Summary of Refutations

Below are summaries and excerpts from the source articles. Some excerpts are quotes from other authors. To appreciate the full force of the arguments and to see the references for quotes read the full articles. The article by Tymn is a summary of the article by Hogan so sometimes only one of these articles is referred to below.

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.
  
  ...
  
  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.
  
  ...
  
  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.
  
  ...
  
  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.
Dying Brain:
- Hogan
  
  1. In the cases where brain disturbances were evident on the patients’ EEG scans, NDEs were less common. [The brain was active but not functioning well, unlike the conditions during NDEs when brain functions stop.
  
  2. In delirium, the person tends to see events occurring at a distance, whereas, in NDEs, experiencers are close to many parts of what is experienced.
  
  3. The effects of delirium brought on by trauma vary widely in content, but NDEs are remarkably consistent across virtually all experiencers regardless of age, nationality, religious background, and all other demographics. 198
  
  Marshall, Lazar, and Spellman wrote in the journal, Brain, that brain physiology is such that many parts of the brain must be coherent for lucid experiences to occur. A disorganized, dying brain couldn't produce the experiences described by near-death experiencers:.
  
  ...
  
  Cerebral damage, particularly hippocampal damage, is common after cardiac arrest; thus only confusional and paranoid thinking as is found in intensive care patients should occur. The paradox is that experiences reported by cardiac arrest patients [during NDEs] are not confusional. On the contrary, they indicate heightened awareness, attention, and memory at a time when consciousness and memory formation are not expected to be functioning.200
  
  Michael Sabom, MD, a cardiologist in Atlanta, Georgia, monitored the brain waves of his patients using an electroencephalograph (EEG) and was able to show that some who had reported NDEs had been clinically dead, meaning they registered no electrical activity in their brain.
- Tymn
  
  Hogan points to research indicating that a dying brain has confusional and paranoid thinking, not the alert thinking and aware observations of the NDEr. He also mentions research by Michael Sabom, M.D. showing that the NDE occurred after the brain had already passed the dying experience.
- Beauregard: See above section on Lack of Oxygen.
- Greyson See source.
- near-death.com See source.
Hallucinations:
- Hogan
  
  1. Incredibly accurate and verifiable information results from the NDE that would not result from a hallucination.
  
  2. People on drugs who have NDEs actually see fewer deceased relatives when they travel out of body. This suggests that people who do see relatives are clear minded, not hallucinating.
  
  3. People see deceased relatives but not living relatives in their NDEs. In some cases, children see dead relatives whom they had never met or seen pictures of. That could not result from a hallucination.212
  
  ...
  
  Turning to the question of whether the NDE was a hallucination (the most common skeptical argument), they [Sabom and Ring] both noted that a hallucination is accompanied by heightened brain activity. But their studies produced data showing that NDEs happened more often when neuroophysiological activity was reduced, not increased. Sabom also found that NDEs were more likely when the person was unconscious for longer than 30 minutes; Ring found that the closer people were to physical death, the more extensive the NDE.213
- near-death.com See section below on brain chemicals.
- Long
  
  The percentage of time that people encounter deceased relatives is extremely high. It was actually 96% in the NDERF study and only 4% of near-death experiencers met beings who were alive at the time of the near-death experience. That’s actually corroborated by another major scholarly study which found it was 95% of the time that they encountered beings they knew from their earthly life that were deceased.
  
  The important thing is that any other experience of altered consciousness that we experience on earth, dreams, hallucinations, drug experiences, you name it; all of these other types of experiences of altered consciousness, a vastly higher percentage of people are going to be alive at the time of their experience.
  
  You're going to remember the banker that you did business with that day or your family member you said hi to as you were walking into the house. This is what's in the forefront of consciousness. So for people to so consistently encounter deceased relatives is very, very strong evidence that they are, indeed, in an unearthly realm and it certainly points to evidence of an afterlife.
  
  ...
  
  People in general, all other hallucinatory events, dreams, all other temporary, transient, even pathological alterations of consciousness are essentially never going to result in that high a percentage of people experiencing them going on and have those types of profound life changes that we see in near-death experiencers.
  
  And moreover, what you see in the life changes of near-death experiencers is markedly consistent. In other words, it’s not just that they have life changes; it’s the consistency of those life changes. The substantial majority, if not overwhelming majority of near-death experiencers believe that there’s an afterlife. They believe that there’s a God. They no longer fear death. They’re less materialistic. They value loving relationships more. The list goes on and on. I consistently observed, not only in the NDERF study but from scores of prior scholarly studies of this phenomenon over 30 years.
Religious Expectations:
- Hogan
  
  The phenomenon is not a result of some religious expectations. If it were fulfilling the experiencer's expectations of what dying is like, we would expect that only people who believed in and expected a near-death experience would have one, not suicides who anticipate annihilation, fundamentalists who expect only to see God, or agnostics and atheists who would not believe in an NDE phenomenon at all. In fact, that is not the case. Carol Zaleski wrote in her book, Otherworld Journeys, describing NDEs, "Suicide victims seeking annihilation, fundamentalists who expect to see God on the operating table, atheists, agnostics and carpe diem advocates find equal representation in the ranks of the near-death experiencers."214
- Tymn Summary of Hogan.
- Long
  
  A really interesting part of the study that I did was looking at children age 5 and under. In fact, their average age was 3-1/2 years old. These are children so young that to them, death is an abstraction. They don’t understand it. They can't conceptualize it. They’ve almost never heard about near-death experiences; have no preconceived notions about that. They certainly have far less cultural influence, both in terms of religion or anything else that could even potentially modify the near-death experience at that tender young age.
  
  And yet looking at these same 33 elements of near-death experience that I did in other parts of this study, I found absolutely no statistical difference in their percentage of occurrence in very young children as compared to older children and adults. So no question about that.
  
  That almost single-handedly shoots down the skeptical argument that near-death experiences are due to pre-existing beliefs or cultural influences. We’re not seeing a shred of evidence that corroborates that at all. In fact, that finding is actually corroborated with another major scholarly researcher who actually reviewed over 30 years of near-death experience research and came up with the same conclusion.
Cultural Expectations:
- Hogan
  
  Margot Grey's study of NDEs in England215; Paola Giovetti's study in Italy216; Dorothy Counts' study in Melanesia217; Satwant Pasricha and Ian Stevenson's study in India218. More studies are coming out from different countries on a regular basis, and historical examples show that the experience has been remarkably consistent over time (see Plato's example of Er's NDE in The Republic).219
- Tymn: "Hogan cites research demonstrating that different cultures have produced remarkably similar findings, thus showing that they're not dependent on expectations in any culture."
- Long
  
  A really interesting part of the study that I did was looking at children age 5 and under. In fact, their average age was 3-1/2 years old. These are children so young that to them, death is an abstraction. They don’t understand it. They can't conceptualize it. They’ve almost never heard about near-death experiences; have no preconceived notions about that. They certainly have far less cultural influence, both in terms of religion or anything else that could even potentially modify the near-death experience at that tender young age.
  
  And yet looking at these same 33 elements of near-death experience that I did in other parts of this study, I found absolutely no statistical difference in their percentage of occurrence in very young children as compared to older children and adults. So no question about that.
  
  That almost single-handedly shoots down the skeptical argument that near-death experiences are due to pre-existing beliefs or cultural influences. We’re not seeing a shred of evidence that corroborates that at all. In fact, that finding is actually corroborated with another major scholarly researcher who actually reviewed over 30 years of near-death experience research and came up with the same conclusion.
Hearing about medical procedures after the fact:
- Tymn
  
  Some debunkers speculate that the NDE is pieced together after a trauma from bits and pieces of information gathered from medical personnel while the experiencer floated in and out of consciousness. Here again, research has shown that experiencers have observed things outside their visual fields and what is going on in the emergency room or trauma scene.
Hearing during resuscitation:
- Hogan
  
  Michael Sabom, MD, examined six cases on record that included visual descriptions and discovered that the reports included visual details the patients could not have observed in their unconscious state, and some details were of events that were outside of their visual fields, even in other rooms.221
- Prescott
  
  The expression "adequately anesthetized" is intended here to exclude cases of literal awakening, or partial awakening, during surgical procedures. Such awakening is known to occur, even using present-day techniques, in something on the order of 0.1-0.3% of all general-surgery procedures. Higher rates occur, as might be expected, when muscle relaxants are used in combination with low levels of anesthetic agents.... The phenomenology of such awakenings, however, is altogether different from that of NDEs, and often extremely unpleasant, frightening, and even painful. The experiences are typically brief and fragmentary, and primarily auditory or tactile, and not visual. [Footnote, page 387]
- Long
  
  Yet there are dozens of these out-of-body perceptions during near-death experiences where they can hear and see events far, far removed from their physical body, often in completely different rooms, geographically far away, where any possible physical sensory awareness should be absolutely impossible.
  
  And yet when they make these very remote out-of-body experience observations, their accuracy is absolutely the same – about 96% — as the observations of events going on around their physical body. So no doubt about that.
  
  ...
  
  In fact, it's often the case that they’ll make out-of-body observations of events right around their physical body during the NDE, and then as part of the same experience, make out-of-body observations far removed from their physical body. Absolutely no difference in what they're describing.
Brain Dysfunction (such as temporal lobe dysfunction):
- Tymn
  
  While temporal lobe seizures produce illusions, hallucinations, and feeling of despair, these negative experiences are clearly not consistent with positive NDEs.
  
  Hogan mentions some interesting research by Carl Becker, Ph.D., professor of comparative thought at Kyoto University and a scholar in bioethics, death, and dying. Becker determined that NDEs are real, verifiable, objective events, as 1) experiencers have clairvoyant or precognitive knowledge they could not have known that is later verified; 2) the NDE is the same across cultures and religions; 3) the NDE is different from religious expectations and are thus not fantasies; 4) in some cases, a third party has observed visionary figures seen by the experiencers, thus indicating that they are not subjective hallucinations.
- Prescott
  
  Persinger has also claimed that "a vast clinical and surgical literature ... indicates that floating and rising sensations, OBEs, personally profound mystical and religious encounters, visual and auditory experiences, and dream-like sequences are evoked, usually as single events, by electrical stimulation of deep, mesiobasal temporal lobe structures". His sole reference for this strong claim is a paper by Stevens (1982). That paper, however, is confined entirely to descriptions of certain physiological observations made in studies of epileptic patients, and it contains no mention whatever of any subjective experiences or of electrical stimulation studies, much less of "a vast clinical and surgical literature" supporting Persinger's claim. Persinger goes on to claim that, using weak transcranial magnetic stimulation, he and his colleagues have produced "all of the major components of the NDE, including out-of-body experiences, floating, being pulled towards a light, hearing strange music, and profound meaningful experiences." However, we have been unable to find phenomenological descriptions of the experiences of his subjects adequate to support this claim, and the brief descriptions that he does provide in fact again bear little resemblance to NDEs (e.g., Persinger, 1994, pages 284-285)....
  
  Neurologist Ernst Rodin stated bluntly: "In spite of having seen hundreds of patients with temporal lobe seizures during three decades of professional life, I have never come across that symptomatology [of NDEs] as part of the seizure." [Pages 382-383]
- Facco and Christian
  
  Therefore, in Britton and Bootzin's study (2004), the tendency toward a temporal lobe dysfunction in patients reporting NDEs, though of interest, might simply be the result of the injury, without any cause-effect relationship with NDEs.
  
  ...
  
  ... near-death-like experiences have been reported in the absence of cerebral dysfunctions (Owens et al., 1990; Gabbard and Twemlow, 1991; Facco and Agrillo, under revision). To that effect, van Lommel (2010) summarized some of the most frequently recurring circumstances that might prompt NDEs in the absence of brain function disorders. These include serious (but not immediately life threatening) conditions, isolation, depression, existential crisis, meditation, and similar experiences (the so-called “fear-death experiences”). Another potential circumstance was described by Moody and Perry (2010), who reported shared death experiences in healthy people attending the moment of death of a close relative.
- Beauregard
  
  ... researchers describe an OBE as a temporary dysfunction of the junction of the temporal and parietal cortex. But, as Pim van Lommel noted, the abnormal bodily experiences described by Blanke and colleagues entail a false sense of reality. Typical OBEs, in contrast, implicate a verifiable perception (from a position above or outside of the body) of events, such as their own resuscitation or a traffic accident, and the surroundings in which the events took place.
- Greyson
  
  The most important objection to the adequacy of all such reductionistic hypotheses is that mental clarity, vivid sensory imagery, a clear memory of the experience, and a conviction that the experience seemed more real than ordinary consciousness are the norm for NDEs. They occur even in conditions of drastically altered cerebral physiology under which the production theory would deem consciousness impossible.
- near-death.com "... the characteristic emotions that result from temporal lobe stimulation are fear, sadness, and loneliness, not the calm and love of a NDE."
- Alexander
  
  Isolated preservation of cortical regions might have explained some of my experience, but were most unlikely, given the severity of my meningitis and its refractoriness to therapy for a week: peripheral white blood cell (WBC) count over 27,000 per mm3, 31 percent bands with toxic granulations, CSF WBC count over 4,300 per mm3, CSF glucose down to 1.0 mg/dl, CSF protein 1,340 mg/dl, diffuse meningeal involvement with associated brain abnormalities revealed on my enhanced CT scan, and neurological exams showing severe alterations in cortical function and dysfunction of extraocular motility, indicative of brainstem damage.
  
  The thalamus, basal ganglia, and brainstem are deeper brain structures (“subcortical regions”) that some colleagues postulated might have contributed to the processing of such hyperrealexperiences. In fact, none of those structures could play any such role without having at least some regions of the neocortex still intact. All agreed in the end that such subcortical structures alone could not have handled the intense neuralcalculations required for such a richly interactive experiential tapestry.
  
  A “reboot phenomenon”—a random dump of bizarre disjointed memories due to old memories in the damaged neocortex, which might occur on restarting the cortex into consciousness after a prolonged system-wide failure, as in my diffuse meningitis. Especially given the intricacies of my elaborate recollections, this seems most unlikely.
  
  Unusual memory generation through an archaic visual pathway through the midbrain, prominently used in birds but only rarely identifiable in humans. It can be demonstrated in humans who are cortically blind, due to damaged occipitalcortex. It provided no clue as to the ultra-reality I witnessed, and failed to explain the auditoryvisual interleaving.
Inhibitory Network Failure:
- Alexander
  
  In an effort to explain the “ultra-reality” of the experience, I examined this hypothesis: Was it possible that networks of inhibitory neurons might have been predominantly affected, allowing for unusually high levels of activity among the excitatory neuronal networks to generate the apparent “ultra-reality” of my experience? One would expect meningitis to preferentially disturb the superficial cortex, possibly leaving deeper layers partially functional. The computing unit of the neocortex is the six-layered “functionalcolumn,” each with a lateral diameter of 0.2– 0.3 mm. There is significant interwiring laterally to immediately adjacent columns in response to modulatory control signals that originate largely from subcortical regions (the thalamus, basal ganglia, and brainstem). Each functional column has a component at the surface (layers 1–3), so that meningitis effectively disrupts the function of each column just by damaging the surface layers of the cortex. The anatomical distribution of inhibitory and excitatory cells, which have a fairly balanced distribution within the six layers, does not support this hypothesis. Diffuse meningitis over the brain’s surface effectively disables the entire neocortex due to this columnar architecture. Full-thickness destruction is unnecessary for total functional disruption. Given the prolonged course of my poor neurological function (seven days) and the severity of my infection, it is unlikely that even deeper layers of the cortex were still functioning.
Retinal dysfunction causing an image of the tunnel:
- Facco and Christian
  
  In a sudden severe acute brain damage event such as cardiac arrest, there is no time for an experience of tunnel vision from retinal dysfunction, given that the brain is notably much more sensitive to anoxia and ischemia than peripheral organs; its role in coma from acute brain lesions (such as trauma or hemorrhage) is also questionable, as the pathophysiology of brain damage does not imply retinal ischemia. Fainting due to arterial hypotension—a common event—does not seem to be associated with the tunnel visions described in NDEs. In a comprehensive review of symptoms and signs of syncope (Wieling et al., 2009), the prodromal visual changes were described as blurred and fading vision, scotomas, color changes, dimming or graying of the peripheral field of vision (“graying out”), followed by peripheral light loss and complete blindness (“blacking out”). Graying out has been clearly described in experimental conditions only, such as during exposure to centrifugal force. There may be a link between graying out and the experience of seeing a tunnel, but the latter is qualitatively different and seems to depend on cultural factors as well (Belanti et al., 2008): in fact, it is usually described as passing through a tunnel and reaching a new landscape (van Lommel et al., 2001; Facco, 2010), while graying out is a much simpler transient sensation usually followed by blackout. These data as a whole make the retinal hypothesis as the main mechanism of tunnel vision plausible at best only for pilots and falls from a high altitude in the mountains.
Visual cortex dysinhibition associated with anoxia causing an image of the tunnel:
- Facco and Christian
  
  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.
- 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.
  
  Also see Lack of oxygen.
Brain chemicals such as ketamine, DMT, etc.:
- Prescott (ketamine)
  
  Unlike the vast majority of NDEs, ketamine experiences are often frightening and involve bizarre imagery, and patients usually express the wish not to repeat the experience. Most ketamine users also recognize the illusory character of their experience, in contrast to the many NDE experiencers who are firmly convinced of the reality of what they experienced and its lack of resemblance to illusions or dreams. Even if ketamine experiences do resemble NDEs in some respects, many important features of NDEs, such as seeing deceased people or a revival of memories, have not been reported with ketamine. Furthermore, ketamine typically exerts its effects in an otherwise more or less normal brain, while many NDEs occur under conditions in which brain function is severely compromised. [Pages 380-381]
- Facco and Christian (endogenous opioids, neurotransmitter imbalance and hallucinogens including DMT)
  
  Endogenous opioids, which are likely released in critical conditions, are only weak hallucinogens, though they might help to evoke vivid experiences, particularly when in combination with cognitive confusion. Nevertheless, NDEs are not reported by patients using opioids for severe pain, while their cerebral adverse effects display an entirely different phenomenology in comparison to NDEs (Mercadante et al., 2004; Vella-Brincat and Macleod, 2007). Morse also found that NDE occurrence in children is independent from drug administration, including opioids (Morse et al., 1986). Therefore, opioids are far from successful at entirely explaining the positive mood and vivid “hallucinations” of NDEs.
  
  The topic of neurotransmitter imbalance and hallucinogens is very complex and far beyond the limits of this analysis; however, even though some psychedelic drugs such as DMT and ayahuasca can give rise to quite similar experiences (Strassman, 2001), aside from providing usable analogies for NDEs, there are marked differences between the hallucinations that accompany use of psychedelic drugs and NDEs, preventing the latter's interpretation as a simple byproduct of the release of specific neurotransmitters (see Facco, 2010, as a review of the topic).
- Beauregard (ketamine)
  
  But ketamine experiences are often frightening, producing weird images; and most ketamine users realize that the experiences produced by this drug are illusory. In contrast, NDErs are strongly convinced of the reality of what they experienced. Furthermore, many of the central features of NDEs are not reported with ketamine.
- Long
  
  The percentage of time that people encounter deceased relatives is extremely high. It was actually 96% in the NDERF study and only 4% of near-death experiencers met beings who were alive at the time of the near-death experience. That’s actually corroborated by another major scholarly study which found it was 95% of the time that they encountered beings they knew from their earthly life that were deceased.
  
  The important thing is that any other experience of altered consciousness that we experience on earth, dreams, hallucinations, drug experiences, you name it; all of these other types of experiences of altered consciousness, a vastly higher percentage of people are going to be alive at the time of their experience.
  
  You're going to remember the banker that you did business with that day or your family member you said hi to as you were walking into the house. This is what's in the forefront of consciousness. So for people to so consistently encounter deceased relatives is very, very strong evidence that they are, indeed, in an unearthly realm and it certainly points to evidence of an afterlife.
- Alexander
  
  Endogenous glutamate blockade with excitotoxicity, mimicking the hallucinatory anesthetic, ketamine (occasionally used to explain NDEs in general). I occasionally saw the effects of ketamine used as an anesthetic during the earlier part of my neurosurgical career at Harvard Medical School. The hallucinatory state it induced was most chaotic and unpleasant, and bore no resemblance whatsoever to my experience in coma.
  
  N,N-dimethyltryptamine (DMT) “dump” (from the pineal, or elsewhere in the brain). DMT, a naturally occurring serotonin agonist (specifically at the 5-HT1A, 5- HT2A and 5-HT2C receptors), causes vivid hallucinations and a dreamlike state. I am personally familiar with drug experiences related to serotonin agonist/antagonists (that is, LSD, mescaline) from my teen years in the early 1970s. I have had no personal experience with DMT but have seen patients under its influence. The rich ultra-reality would still require fairly intact auditory and visual neocortex as target regions in which to generate such a rich audiovisual experience as I had in coma. Prolonged coma due to bacterial meningitis had badly damaged my neocortex, which is where all of that serotonin from the raphe nuclei in the brainstem (or DMT, a serotonin agonist) would have had effects on visual/auditory experience. But my cortex was off, and the DMT would have had no place in the brain to act. The DMT hypothesis failed on the basis of the ultra-reality of the audiovisual experience, and lack of cortex on which to act.
REM Intrusions:
- Facco and Christian
  
  The hypothesis of REM intrusions (Nelson et al., 2006) is not compatible with cardiac arrest, a condition in which brain electrical activity is silent...
- Long
  
  The percentage of time that people encounter deceased relatives is extremely high. It was actually 96% in the NDERF study and only 4% of near-death experiencers met beings who were alive at the time of the near-death experience. That’s actually corroborated by another major scholarly study which found it was 95% of the time that they encountered beings they knew from their earthly life that were deceased.
  
  The important thing is that any other experience of altered consciousness that we experience on earth, dreams, hallucinations, drug experiences, you name it; all of these other types of experiences of altered consciousness, a vastly higher percentage of people are going to be alive at the time of their experience.
  
  You're going to remember the banker that you did business with that day or your family member you said hi to as you were walking into the house. This is what's in the forefront of consciousness. So for people to so consistently encounter deceased relatives is very, very strong evidence that they are, indeed, in an unearthly realm and it certainly points to evidence of an afterlife.
  
  ...
  
  People in general, all other hallucinatory events, dreams, all other temporary, transient, even pathological alterations of consciousness are essentially never going to result in that high a percentage of people experiencing them going on and have those types of profound life changes that we see in near-death experiencers.
  
  And moreover, what you see in the life changes of near-death experiencers is markedly consistent. In other words, it’s not just that they have life changes; it’s the consistency of those life changes. The substantial majority, if not overwhelming majority of near-death experiencers believe that there’s an afterlife. They believe that there’s a God. They no longer fear death. They’re less materialistic. They value loving relationships more. The list goes on and on. I consistently observed, not only in the NDERF study but from scores of prior scholarly studies of this phenomenon over 30 years.
Epilepsy or seizures:
- Beauregard
  
  A review of the literature on epilepsy, however, indicates that the classical features of NDEs are not associated with epileptic seizures located in the temporal lobes.
Psychopathology: also see sections: defense against dying, hallucinations, religious expectations, cultural expectations
- Hogan
  
  There is little evidence or reason to believe that these experiences represent psychiatric pathology or dysfunction, according to German psychiatrist Michael Schroeter.204 They can be easily distinguished from hallucinations of schizophrenia or organic brain dysfunction.205,206 NDEs are predominantly positive and lack the paranoid ideation, distortions of reality, negative imagery, olfactory elements, and aggressive and hostile elements of drug-induced hallucinations or other transient psychoses.207,208 They represent an acknowledgment of reality, whereas intensive care unit psychosis usually represents a denial of reality.209 They occur to people in excellent mental health, who have a similar capacity for fantasy, as well as similar repressed anxieties as the typical population.210 To explain NDEs as depersonalization or regression into the psychologic state before ego differentiation ignores the clinical experiences of the subjects, which are experienced with intact ego identity.211
- Tymn
  
  Some debunkers have suggested that NDEs are a result of mental instability. Hogan cites research indicating that NDE subjects were actually significantly healthier than psychiatric inpatients and outpatients and somewhat healthier than college students. He quotes Dr. Melvin Morse as saying that NDEs are predominantly positive and an acknowledgement of reality.
- Greyson
  
  Although the theories and evidence provided by Joseph (1996, 1999b, 2001a) and others is intriguing, they only provide empirical support and address only selected aspects of the phenomena (Greyson et al., 2009). The most important objection to the adequacy of all such reductionistic hypotheses is that mental clarity, vivid sensory imagery, a clear memory of the experience, and a conviction that the experience seemed more real than ordinary consciousness are the norm for NDEs. They occur even in conditions of drastically altered cerebral physiology under which the production theory would deem consciousness impossible.
Unique Personality Traits:
- Greyson See section on Psychopathology.
Residual brain activity during unconsciousness:
- Greyson
  
  In cardiac arrest, even neuronal action-potentials, the ultimate physical basis for coordination of neural activity between widely separated brain regions, are rapidly abolished (Kelly et al., 2007). 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). In short, it is not credible to suppose that NDEs occurring under conditions of general anesthesia, let alone cardiac arrest, can be accounted for in terms of some hypothetical residual capacity of the brain to process and store complex information under those conditions.
- Alexander
  
  The distorted recall of memories from deeper parts of the limbic system (for example, the lateral amygdala) that have enough overlying brain to be relatively protected from the meningitic inflammation, which occurs mainly at the brain's surface ... did not explain the robust, richly interactive nature of the recollections.
The experience occurred before or after brain activity stopped:
- Greyson
  
  However, unconsciousness produced by cardiac arrest characteristically leaves patients amnesic and confused for events immediately preceding and following these episodes (Aminoff et al., 1988; Parnia & Fenwick, 2002; van Lommel et al., 2001). Furthermore, a substantial number of NDEs contain apparent time "anchors" in the form of verifiable reports of events occurring during the period of insult itself. For example, a cardiac-arrest victim described by van Lommel et al. (2001) had been discovered lying in a meadow 30 minutes or more prior to his arrival at the emergency room, comatose and cyanotic, and yet days later, having recovered, he was able to describe accurately various circumstances occurring in conjunction with the ensuing resuscitation procedures in the hospital.
  
  Also see the next section below: The experience occurred during CPR
The experience occurred during CPR:
- Long
  
  When you talk to the patients who have actually survived CPR, one thing that is very, very obvious is that the substantial majority of them are confused or amnesic, even when they're successfully recovered. They may be amnesic for the period of time following their successful resuscitation or even for events prior to the time of their cardiac arrest.
  
  ...
  
  If you read even a few near-death experiences, you immediately realize that there’s essentially none of them that talk about episodes of confusion or altered mental status when they just don’t understand what’s going on. You really don’t see that at all.
  
  Again, for near-death experiences, they're highly lucid, organized events. In fact, in the survey we did, we found 76% of people having a near-death experience said their level of consciousness and alertness during the NDE was actually greater than their earthly, everyday life. So again, getting back to statistics, that’s 3/4 and a substantial majority of the remaining 24% still had at least a level of consciousness and alertness equal to their earthly, everyday life.
  
  So for that to be the statistics that you consistently see during near-death experiences and balance that with a substantial majority of people being confused around the time of their successful resuscitation from CPR, you really have to come away with the conclusion that even if there’s blood flow to the brain induced by CPR, it's a life-saving maneuver. By no means is that correlated with clear consciousness and certainly nowhere near the level of consciousness and alertness with near-death experiences. You just don’t see that.
  
  But also, in addition to that, note that the substantial majority of people that have a near-death experience and have an out-of-body experience associated with cardiac arrest, are actually seeing their physical body well prior to the time that CPR is initiated. Once CPR is initiated, you don’t see any alteration in the flow of the near-death experience, suggesting that whatever blood flow might be going back to the brain is affecting the content, modifying it at all, in any way.
  
  ...
  
  When there’s a cardiac arrest, the out-of-body observations that are often described during these near-death experiences certainly correlates to a time prior to CPR being initiated, and prior to a time there should be no possibility of a conscious, lucid, organized experience. And yet that’s exactly what happens.
  
  I'll tell you another thing, too, is if you were doing CPR and that were accounting for memory, I would tell you that you would hear a lot more from near-death experiencers. They would talk about their remembrance of the pain of the chest compressions.
  
  Alex, that’s a fairly painful procedure. It often breaks ribs and hurts. And yet, even when you have a patient who had a cardiac arrest and had a near-death experience, essentially never do you hear them describing as part of their near-death experience the pain of chest compressions.
  
  ...
  
  And if their consciousness was really returning during CPR, wouldn't near-death experiencers not have out-of-body perceptions but describe their perceptions from within their physical body? And yet you don’t see that with near-death experiences.
  
  So in other words, if you started CPR and they had a near-death experience and suddenly they started to have some consciousness, you’d expect that instead of having the out-of-body experience where their consciousness is apart from their body, their consciousness would be within their body. You just don’t see that.
Evolutionary Adaptation:
- near-death.com
  
  But this theory does not explain why NDEs are erratic, or why we shunted down an evolutionary sidetrack for years by making them something that people were reluctant to talk about. After all, in Darwinian terms, humans are the complete masters of the Earth.
- Alexander
  
  A primitive brainstem program to ease terminal pain and suffering ("evolutionary argument"- possibly as a remnant of "feigned-death" strategies from lower mammals?) ... did not explain the robust, richly interactive nature of the recollections.
Depersonalization:
- Hogan
  
  Another common explanation is that the NDE occurs because of depersonalization, meaning it is simply a self-defense mechanism as the person is confronted with non-existence. But this conflicts with the feeling of the enhanced self-identity that invariably occurs in an NDE. Furthermore, if the event is only a physical-brain reaction, it would have to be in a dream-like state where finer details are missing, but the NDE is marked by the absolute clarity.
  
  Also, the traumatized patients often don’t realize they are in a life-threatening situation and enter unconsciousness suddenly, without consciously considering whether they’re dying.
- near-death.com
  
  ... some typical features of a NDE just do not fit into the depersonalization mode, such as the strong spiritual and mystical feelings, and the increased alertness and awareness.
Memory of birth:
- near-death.com
  
  a baby being born does not exactly float at high speed down a tunnel, but is buffeted along with difficulty by its mother's contractions. And how does this model explain the meeting with friends and relatives who have died? The "Being of Light" is supposed to be the midwife or the doctor who rules the delivery room - but many babies are born without a midwife or doctor present, or perhaps with many people present. On a purely practical level, a baby's nervous system is not sufficiently developed to allow it to assimilate and store memories of the birth process.
  
  Those who argue this theory say that the feelings of peace and bliss are a memory of the peace of the womb when all physical needs were met by the mother and there were no stresses and strains. Why should this be any more likely than the feelings of peace and bliss are relief from the pain of illness and injury at the point of death? However, being born is often not a pleasant experience for babies which leaves them crying as if in agony. In contrast, NDEs are more often described as the most pleasurable experience a person can have. The birth process is not pleasant.
Medication:
- Hogan
  
  The reports are of sensations and consciousness that are more lucid than normal, an effect opposite to that of a brain clouded by drugs.
  
  Michael Sabom, a cardiologist on staff at Northside and Saint Joseph’s Hospitals in Atlanta, Georgia, studied the experiences described in NDEs and concluded that they are quite different from hallucinations induced by drugs.194
  
  Hogan also qotes Melvin Morse:
  
  In the case of the suggestion that mind-altering medication causes the NDE, Melvin Morse has produced a study where a group of one hundred and twenty-one children were seriously ill, but had less than a five per cent chance of dying, and yet none had an NDE [because they had not been near death]. Of another thirty-seven children who had received many forms of mind-changing drugs, again, there were no NDEs. However, in another group of twelve children who had suffered a cardiac arrest, eight of these recalled having an NDE. A considerable amount has been written by medical professionals that demonstrates that medication cannot be the cause of the NDE.195
- Tymn: "...there are numerous NDEs not involving medication or drugs...Hogan cites the research of Michael Sabom, a Georgia cardiologist, and Melvin Morse, a professor of pediatrics, both demonstrating that the experiences are quite different from hallucinations caused by drugs..."
- Facco and Christian
  
  ... 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.
- It has been reported that Naloxone causes hellish NDEs which would suggest there is a physiological cause of NDEs. However, this claim is a misrepresentation of the facts that does not stand up under close scrutiny. Naloxone is used to treat overdoses of narcotic drugs and itself can cause hallucinations. The claim it caused an NDE is based on one case of a patient who was semiconscious and his experience lacked the common characteristics of NDEs and included elements typical of drug-induced hallucinations not seen in NDEs.
Defense against dying:
- Tymn
  
  Debunkers also claim that the NDE is simply a self-defense mechanism for the person who is confronted with extinction. "But this conflicts with the feeling of the enhanced self-identity that invariably occurs in an NDE," Hogan points out, going on to mention that this theory suggests a dream-like state, whereas NDEs are marked by absolute clarity.
Partial anesthesia:
- Prescott
  
  The expression "adequately anesthetized" is intended here to exclude cases of literal awakening, or partial awakening, during surgical procedures. Such awakening is known to occur, even using present-day techniques, in something on the order of 0.1-0.3% of all general-surgery procedures. Higher rates occur, as might be expected, when muscle relaxants are used in combination with low levels of anesthetic agents.... The phenomenology of such awakenings, however, is altogether different from that of NDEs, and often extremely unpleasant, frightening, and even painful. The experiences are typically brief and fragmentary, and primarily auditory or tactile, and not visual. [Footnote, page 387]
- Long
  
  Rather than the type of coherent NDEs you read here, anesthetic-awareness results in a totally different experience.
  
  ...
  
  Those who experience anesthetic-awareness often report very unpleasant, painful and frightening experiences. Unlike NDEs which are predominately visual experiences, this partial awakening during anesthesia more often involves brief and fragmented experiences that may involve hearing but usually not vision.
  
  ... you just don’t have near-death experiences that are predominately hearing but no vision.
  
  ...when we talked about near-death experiences under general anesthesia, out of 33 elements of near-death experience, we compared between NDEs under general anesthesia and all types of causes of near-death experience, and in 32 out of 33 elements studied there was no statistical difference between the two groups.
  
  Now, virtually anybody in the science or medical field would say, “Well, that pretty much nails it down that these two experiences are basically the same, with at most, minor differences between the two of them.
Misuse of anecdotes:
- Long
  
  ... the NDERF study that I presented in the book is certainly vastly beyond anecdotal evidence. We actually studied 1,300 near-death experiences. It’s certainly not just a limited number of case reports. And you’re right, our modern questionnaire is over 150 questions, so no doubt we have the depth of analysis, as well. And most of the research that’s published in the book was based on surveying over 600 near-death experiencers that filled out the most recent version of the questionnaire.
  
  Let me start out with sort of a basic scientific overview, and that is what’s real is consistently observed. So we’ve observed evidence of the afterlife and near-death experience is not only in the vast number of near-death experiences studied in tremendous depth in my own study, but all my major findings are corroborated by scores of prior scholarly studies. We’re way beyond what could reasonably be called anecdotal. We’re really in very hard-core evidence based on my work and the work of many others.
Selective reporting:
- Long
  
  What we did with our NDERF study is we studied every single person who had a near-death experience. In other words, they nearly died and they had an experience.
  
  In addition to that, we used the most validated research tool in near-death experience research, and that’s called the NDE scale. So we analyzed every single person that had such an account. In fact, we post every single near-death experience on the website for the people who give us permission, which is over 95%. So we not only have a very valid, comprehensive look at near-death experience because of the numbers, but in addition to that we share that with the world, so everybody else can see the data set that we’re seeing, too.

Detailed list of hypotheses refuted by each source:

Chapter 2 in "Your Eternal Self by R. Craig Hogan, Ph.D. (Search for the header: "Purely Physiological Explanations for the NDE Accounts Have Been Shown to Be Insufficient to Account for Them.")