A 13-year Dutch study led by Pim van Lommel and published in Lancet found that 12 percent (or 18 percent, depending on how NDE is defined) of 344 resuscitated patients who had experienced cessation of their heart and/or breathing function reported an NDE. If the cause of the NDE were purely physiological, the researchers reasoned that all of the patients should have had one because of their similar plight. Psychological factors were ruled out by the researchers, as were the medications taken by the patients. However, the researchers believe that
neurophysiological processes must play some part in NDE. Similar experiences can be induced through electrical stimulation of the temporal lobe (and hence of the hippocampus) during neurosurgery for epilepsy, with high carbon dioxide levels (hypercarbia), and in decreased cerebral perfusion resulting in local cerebral hypoxia as in rapid acceleration during training of fighter pilots, or as in hyperventilation followed by Valsalva manoeuvre. Ketamine-induced experiences resulting from blockage of the NMDA receptor, and the role of endorphin, serotonin, and enkephalin have also been mentioned, as have near-death-like experiences after the use of LSD, psilocarpine, and mescaline. These induced experiences can consist of unconsciousness, out-of-body experiences, and perception of light or flashes of recollection from the past. These recollections, however, consist of fragmented and random memories unlike the panoramic life-review that can occur in NDE. Further, transformational processes with changing life-insight and disappearance of fear of death are rarely reported after induced experiences.
Thus, induced experiences are not identical to NDE...*
The Dutch researchers seem to be assuming that no significant life-insight changes occur in people who have had induced NDE-like experiences. They cite no evidence that this is so. In any case, the proper conclusion should be that the effect of induced experiences is not identical to the effect of "natural" NDEs.
We can't assume that those who report NDEs had an NDE. Nor can we be sure that only those who report having had an NDE actually had one.
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Source:
http://skepdic.com/nde.html