Excerpted from
http://www.mindspring.com/~scottr/nde/jansen1.html:
"Near-death experiences (NDE's) can be
reproduced by ketamine via blockade of receptors in the brain (the N-methyl-D-aspartate, NMDA receptors) for the neurotransmitter glutamate. Conditions which precipitate NDE's (hypoxia, ischaemia, hypoglycaemia, temporal lobe epilepsy etc.) have been shown to release a flood of glutamate, overactivating NMDA receptors resulting in neuro ('excito') toxicity. Ketamine prevents this neurotoxicity. There are substances in the brain which bind to the same receptor site as ketamine. Conditions which trigger a glutamate flood may also trigger a flood of neuroprotective agents which bind to NMDA receptors to protect cells, leading to an
altered state of consciousness like that produced by ketamine. This article extends and updates the theory proposed in 1990 (Jansen, 1990b).
The near-death experience (NDE) is a phenomenon of considerable importance to medicine, neuroscience, neurology, psychiatry, philosophy and religon (Stevenson and Greyson, 1979; Greyson and Stevenson, 1980; Ring, 1980; Sabom, 1982; Jansen, 1989a,b, 1990b). Unfortunately, some scientists have been deterred from conducting research upon the NDE by claims that NDE's are evidence for life after death, and
sensationalist media reports which impart the air of a pseudoscience to NDE studies. Irrespective of religous beliefs,
NDE's are not evidence for life after death on simple logical grounds: death is defined as the final, irreversible end. Anyone who 'returned' did not, by definition, die - although their mind, brain and body may have been in a very unusual state.
There is overwhelming evidence that 'mind' results from neuronal activity. The dramatic effects on the mind of adding hallucinogenic drugs to the brain, and the religious experiences which sometimes result, provide further evidence for this (Grinspoon and Bakalar, 1981).
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" (Morse, 1989, original italics).
...
Ketamine administered by intravenous injection, in appropriate dosage, is
capable of reproducing all of the features of the NDE which have been commonly described in the most cited works in this field, and the following account is based upon these (Domino et al., 1965; Rumpf, 1969; Collier, 1972; Siegel,1978, 1980, 1981; Stafford, 1977; Lilly, 1978; Grinspoon and Bakalar, 1981; White, 1982; Ghoniem et al., 1985; Sputz, 1989; Jansen, 1989a, b,1990b, 1991c, 1993). Important features of NDE's include a sense that what is experienced is 'real' and that one is actually dead, a sense of ineffability, timelessness, and feelings of calm and peace, although some cases have been frightening. There may be analgesia, apparent clarity of thought, a perception of separation from the body, and
hallucinations of landscapes, beings such as 'angels', people including partners, parents, teachers and friends (who may be alive at the time), and religious and mythical figures. Transcendant mystical states are commonly described. Memories may emerge into consciousness, and are rarely organised into a 'life review' (Greyson, 1983).
Hearing noises during the initial part of the NDE has also been described (Noyes and Kletti, 1976a; Morse et al., 1985; Osis and Haraldsson, 1977; Greyson and Stevenson, 1980; Ring, 1980; Sabom, 1982). Ring (1980) classified NDE's on a 5 stage continuum: 1.feelings of peace and contentment; 2.a sense of detachment from the body; 3. entering a transitional world of darkness (rapid movements through tunnels: 'the tunnel experience'); 4. emerging into bright light; and 5. 'entering the light'. 60% experienced stage 1, but only 10% attained stage 5 (Ring, 1980). As might be expected in a mental state with a neurobiological origin,
more mundane accounts also occur, e.g. children who may 'see' their schoolfellows rather than God and angels (Morse, 1985). It is clear that NDE's are not as homogeneous as some have claimed.
...
A psychologist with experience of LSD described ketamine as 'experiments in voluntary death' (Leary, 1983, p375). Sputz (1989, p65) noted:'one infrequent ketamine user reported a classic near-death experience..."
I was convinced I was dead. I was floating above my body. I reviewed all of the events of my life and saw a lot of areas where I could have done better". The psychiatrist Stanislav Grof stated:
"If you have a full-blown experience of ketamine, you can never believe there is death or that death can possibly influence who you are" (Stevens, 1989, p481-482). '
Ketamine allows some patients to reason that ...the strange, unexpected intensity and unfamiliar dimension of their experience means they must have died..' (Collier, 1981, p552).
...
Hypercarbia:
a CO2-enriched breathing mixture can result in typical NDE phenomena such as bodily detachment and the perception of being drawn towards a bright light.
...
2. Regression in the service of the ego:
confronting death cuts off the external world resulting in regression to a pre-verbal level. This is experienced as mystical ineffability (Greyson, 1983). Losing contact with the external world is one of the most typical effects of ketamine. This is partially due to blockade of NMDA receptors involved in sensory transmission. NMDA receptors play a central role in the transmission of data from all sensory modalities (Davies and Watkins, 1983; Greenamyre et al., 1984; Headley et al., 1985; Cotman et al., 1987; Cline et al.,1987; Monaghan, Bridges and Cotman, 1988; Kisvardy et al., 1989; Oye et al., 1992).
3. State dependant reactivation of birth memories (Grof and Halifax, 1977). Movement through tunnels towards light
may be a memory of being born : a 'near-birth experience'. NMDA receptor blockade could be the mechanism for such a reactivation of primitive memories.
4. Sensory deprivation: memories may normally be suppressed by a 'gate' which admits primarily external signals when we are fully conscious and concentrating upon an external task (Siegel,1980, 1981). If this input is dramatically reduced (e.g. by ketamine or a heart attack) in combination with central stimulation (e.g. by excessive glutamate release during hypoxia, epilepsy, or arising without external provocation),
stored perceptions are released and become 'organised' into a meaningful experience by psychodynamic forces in the mind in question (Greyson, 1983). The 'white light' may result from CNS stimulation , and also a possible lowering of the phosphene perceptual threshold (Siegel,1980, 1981).
Sensory deprivation can produce profound alterations in consciousness (Lilly, 1961,1978).
...
Spiritualists have sometimes seen scientific explanations of NDE's as
dull and reductionist. However, the exploration of the mind-brain interface is one of the most
exciting adventures which humans have ever undertaken.
The real reductionism lies in attempts to draw a mystical shroud over the NDE, and to belittle the substantial evidence in favour of an scientific explanation."
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Topic: Debunking Near Death Experiences (NDEs) (Read 4529 times)
August 02, 2010, 05:59:07 pm
