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Near death experiences. What causes that?

  1. Aug 13, 2004 #1
    Near death experiences implie a set of diverse perceptions or hallucinations.
    Two or three years ago, a team was able to induce with electrodes out of body experiences.
    What are the biological causes of near death experiences?
    Is there any explanation from an evolutive viewpoint?
  2. jcsd
  3. Aug 14, 2004 #2
    I have read that DMT is secreted via the pineal gland during near death experiences. DMT is one of the most potent hallucinogens known to man.

    Indians and such would try to focus their meditative powers on the "third eye" (the pineal) in order to stimulate it to produce DMT, then they would travel to great places and have spiritual encounters.
  4. Aug 14, 2004 #3
    I remember watching a documentary about death that was on about people seeing "white light at the end of a tunnel" as near death experience. However, this is an effect that is experienced also when humans are subjected to high accelerations. I can't remember exactly what the logic was but the documentary seemed to portray that this "white light at the end of a tunnel" effect is an illusion that results from the way brain works.
  5. Aug 22, 2004 #4
    The basic question would be: If near death experiences are evoked by some neurotransmitters, What would be its usefulness? Or, similarly, why these experiences are conserved by evolution?
  6. Aug 23, 2004 #5

    Ivan Seeking

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    Some scientists feel that many questions remain. For example, NDE are found where no brain function is seen in the normal EEG's during the perceived experience. Given this, whether they be hallucinations or genuine memories of events in the ER or elsewhere, the fact that detailed and clear memories are formed under these conditions is difficult to explain. Apparently "deep" brain waves are found that are not detected with a normal EEG, but how these deep functions would allow for complex memory formation is apparently not well understood.
  7. Aug 23, 2004 #6


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    During a near-death experience, the body is in a crisis. It is not so difficult to imagine that the brain becomes disorganized and there is a release of stress hormones.

    I once saw an experiment where they isolated people in a dark and sound-proof room. They stimulated the person's head with electrodes and asked what their sensations were. Certain areas provoked a feeling like there was someone in the room, while other areas provoked the vision of light. It would be interesting to look up the experiment and see whether repeat experiments were done.
  8. Aug 25, 2004 #7
  9. Aug 25, 2004 #8
  10. Aug 25, 2004 #9

    Ivan Seeking

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    Until this can be explained the rest is moot.

  11. Aug 25, 2004 #10
    Is death a biological "singularity"?

    NDE would be considered as a form of conscience. They aren't perceived as hallucinations by the subjects neither by the observers. So, the explanation of NDE could be so difficult as the explanation of conscience by mechanistic hypothesis.
    Furthermore, it seems that it is need a lot of scientific observations and, perhaps, controlled experiments with electrodes or chemicals in healthy subjects to search manifestations of NDE.
    I think that it is particulary important a best scientific control of out-of-body experiences.
    Death is associated to irreversibility. But dying has a duration.
    By far analogy to physics, could we see the dying process as an entry into a form of biological "singularity"? If so, both observation and experimentation would constitute a very hard problem.
  12. Aug 26, 2004 #11


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    The following is an abstract of a presentation on the topic of ketamine and NDEs by Karl Jansen of the University of Auckland. The presentation itself was pretty much word for word what is included in the abstract.

    Abstract: Ketamine is a dissociative anesthetic with powerful hallucinogenic and psychedelic properties, including out-of-body experiences, transcendence of time, an extension of awareness beyond consensus reality into other universes, and other effects. Ketamine can produce every feature of a near-death experience (NDE) (Jansen 2001), including the conviction that one has died, awareness leaving the body, ringing/buzzing/ whistling sounds followed by travel through a tunnel at high speed, emerging into light, communion with God, and a life review.
    Because we know how ketamine acts in the brain, this provides us with an understanding of how NDE’s arise. Ketamine blocks ion channels attached to NMDA receptors, and causes a blockage so that salts cannot enter the cell. The neurotransmitter glutamate crosses the gap between cells and binds to NMDA receptors, turning the chemical key which should allow ions to enter the cell. However, while the tunnel is blocked by ketamine, this is not possible.

    NDE’s also involve blockade of NMDA receptors. A sudden fall in O2 or blood sugar, a rise in CO2 (e.g. during a heart attack), and other factors cause a flood release of glutamate. This over-excites cells which die. This is called ‘excito-toxicity’. The glutamate flood also activates apoptotic genes which trigger the cell to commit suicide. Ketamine can prevent this brain damage via the same mechanism which is important to its psychedelic effects: blockade of channels so that ‘the ion sea’ cannot rush into the cells. This led to the prediction that the brain would have its own, natural protective mechanisms against the glutamate flood (Jansen 2001). There would be a huge evolutionary advantage in the development of a protective mechanism involving a counter-flood of natural NMDA receptor-complex blockers, producing ketamine-like NDE effects. While a person is having an NDE at the psychological level, the brain is thus protecting itself from excito-toxic damage. Natural blockers include NAAG (N-acetyl-aspartyl-glutamate), magnesium and kynurenic acid, all of which protect cells from excito-toxic damage.
    People deprived of oxygen for long periods, e.g. after a heart attack, and who report NDE’s, sometimes survive with unimpaired brains. This lack of damage may result from an inherited mechanism for blocking over-excitation. Thus people who can have an NDE may be less likely to suffer brain damage. These may be the same group who report psychedelic experiences with ketamine. Dreams, ketamine ‘journeys’ and NDE’s are all states in which there is a dramatically reduced sensory input from the outside world. Those who do not recall dreams also do not recall ketamine ‘journeys’. The % who recall dreams is about the same as the % reporting ‘emergence phenomena’ after ketamine: about 40%, which is the % of the population who have had some kind of NDE. Genetic differences may be responsible, expressing themselves as different forms of NMDA receptors.

    Ref: Jansen KLR (2001a) Ketamine: Dreams and Realities. Sarasota, Florida: Multidisciplinary Association for Psychedelic Studies (ISBN 0-9660019-3-1) (Available from www.maps.org).
  13. Aug 26, 2004 #12

    Ivan Seeking

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    One key element of the NDE is the assimilation of real, new information. This is not mentioned.
  14. Aug 28, 2004 #13
    I have just read the interesting article of van Lommel et al published in The Lancet 2001;358:2039 http://www.ncbi.nlm.nih.gov/entrez/...ve&db=pubmed&dopt=Abstract&list_uids=11755611 (That links only to abstract)
    These authors made a prospective study on survivors of cardiac arrest. They found a NDE core experience in 12% of survivors.
    From their results, I find very interesting the fact that "no medical, pharmacological or psychological factor affected the frequency of the experience". It is also very interesting the description of a "veridical out-of-body experience of a resuscitated patient".
  15. Aug 31, 2004 #14
    Autoscopy and Out-of-Body Experience

    Out of body experiences would be the most interesting and testable elements of a NDE.
    A similar phenomenon related to out-of-body experiences is Autoscopy, defined as a visual experience where the subject sees an image of him/herself in external space, viewed from within his/her own physical body. Such experience seems to be linked to neurological / psychiatric pathology, Searching in PubMed, I found only 30 citations using "autoscopy" as search criterion.
  16. Sep 7, 2004 #15
    In a search in PubMed on NDE and ketamine, I have found only two references: (both of Jansen):
    A review of the nonmedical use of ketamine: use, users and consequences.
    J Psychoactive Drugs. 2000 Oct-Dec;32(4):419-33.

    Neuroscience and the near-death experience: roles for the NMSA-PCP receptor, the sigma receptor and the endopsychosins.
    Med Hypotheses. 1990 Jan;31(1):25-9.

    Searching by Jansen KL, I have found 28 references, from which only three seems to reflect his hypothesis.

    So, I think that the ketamine hypothesis is lacking of enough scientific basis at the moment.
  17. Sep 7, 2004 #16
    OBEs and NDEs

    One thing about near death experiences that science has yet to explain is that some NDEs include OBEs (out of body experience) where people have saw from a perspective outside of their bodies and desribe events that would be impossibe to view from "inside' the body. Some have even traveled to other rooms in a hospital and are able to desribe physical events and things.

    I am currently going to be reading the best selling book (from the 70s) "Life After Life" by Dr. Raymond Moody. I suggest it if you wish to hear about NDEs

  18. Sep 8, 2004 #17
    Wow wow! Wait! What is NDE, DMT and EEG?
  19. Sep 8, 2004 #18
    I have read the Moody's book. It is only a descriptive book, although interesting, entitled with the conclusion: There is life after death.

    With independence of personal conclusions on life after death, I think interesting the study of the biological substrates of the near death experience. Ia agree: the topic most difficult to be explained is the out-of-body experience. Nevertheless, it was recorded a similar experience with electrode stimulation. Autoscopy is a rare phenomenon with some analogies to the out-of-body experience.
  20. Sep 8, 2004 #19

    NDE: Near Death Experience

    DMT: N,N-Dimethyltryptamine

    EEG: Electroencephalogram
  21. Sep 8, 2004 #20
    I have just read this abstract http://www.ncbi.nlm.nih.gov/entrez/...ve&db=pubmed&dopt=Abstract&list_uids=15002845

    Do you have more information from peer-review jorunals on DMT and NDE?
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