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At last year's first International Medical Conference on Near-Death Experience, held in Martigues, France, eight participants describing themselves as "a group of dedicated physicians and researchers working in different scientific fields" released a statement. They said that while the NDE is mediated by chemical changes in the brain, "its extremely rich and complex content cannot be reduced to a mere illusion." It is of the "utmost importance," they argued, "that scientists wishing to understand the nature of human consciousness conduct research without prejudice."
So what's so baffling about NDEs? We know that when a person's heart stops, the decline in brain function caused by a cut in blood supply is steep. Simultaneous recording of heart rate and brain output shows that within 11 to 20 secs. of the heart failing, the brain waves go flat. A flat electroencephalogram (EEG) recording doesn't suggest mere impairment. It points to the brain having shut down. Longtime NDE researcher Pim van Lommel, a retired Dutch cardiologist, has likened the brain in this state to a "computer with its power source unplugged and its circuits detached. It couldn't hallucinate. It couldn't do anything at all."
Yet it's in this period, between switch-off and resuscitation, that many researchers believe NDEs occur. "Many near-death experiencers describe heightened perceptions and clear thought processes, and form memories, at a time when the brain is incapable of coordinated activity," says Greyson, director of the University of Virginia's Division of Perceptual Studies. "Our current neurophysiological models can explain NDEs only if one ignores much of the empirical data."
Of the thousands of NDEs reported, none has done more to convince some researchers that the phenomenon's explanation must lie outside the square than the case of Pam Reynolds, an American who underwent brain surgery for an aneurysm in 1991. Preparation for Reynolds' operation included taping her eyes shut, blocking her ears and monitoring her EEG to ensure her brain was functioning at only the most basic level. Yet after coming around, Reynolds described not only a full-blown NDE but the bone saw that had been used to cut her skull.
For many years, says cardiologist van Lommel, he was in the first camp on NDEs, sure their basis was entirely material. His interest having been pricked in the mid-'70s by the first book about NDEs, Life After Life by American doctor Raymond Moody, van Lommel in 1988 began a study that would encompass 344 survivors of cardiac arrest in 10 Dutch hospitals. Van Lommel and his co-authors wrote in The Lancet in 2001 that 18% of subjects reported some recollection of the time of clinical death, and 7% an experience that qualified as a deep NDE.
The Dutch team found little about the NDErs that distinguished them as a group from those for whom clinical death was a blackout. Factors such as psychological profile, medications, religion and previous knowledge about NDEs all appeared to be irrelevant. To this day, Van Lommel can't explain why some people have NDEs and most don't. But the fact the experience isn't universal undermines, to his mind, a purely physiological explanation: if lack of oxygen were the cause of NDEs, then all survivors of cardiac arrest should have one.
A few years ago, Van Lommel retired from cardiology to concentrate on NDE research. "I'm lecturing all over the world," he says. "I know all the skeptical questions and I love to answer them." In trying to account for NDEs, he's challenged ideas residing in the bedrock of science, including that consciousness and memories are localized in the brain. As astounding as it may be, he argues, the implication of NDEs is that consciousness can be experienced in some alternative dimension without our body-linked concepts of time and space. "In my view, the brain is not producing consciousness, but it enables us to experience our consciousness," he says. He compares the brain to a television, which receives programs by decoding information from electromagnetic waves. Likewise, he says, "the brain decodes from only a part of our enhanced consciousness, which we experience as waking consciousness. But our enhanced consciousness is different, and this is what is experienced during an NDE."
The idea that the brain can be retuned to alternative states resonates with psychiatrist Jansen, who's written prolifically on how an NDE (or something closely resembling it) can be induced by an anesthetic drug, ketamine. That NDEs can be induced led him at first to suspect that the spontaneous type was similarly hallucinogenic. Now he's not so sure. Perhaps ketamine and brain stress simply make certain states more accessible. "All our realities are alternative realities," says Jansen. "Nobody sees the world in quite the same way as any other person."
Jansen once wrote: "It's good to have an open mind, but not so open that your brain falls out." For many scientists, this scenario might account for the sort of speculation just summarized. While most researchers concede that there's a lot about NDEs we don't know, they reject the push to replace tried-and-tested paradigms with new (largely untestable) ones in an attempt to fill the gaps.
Outside of cardiac arrest and the injection of ketamine, NDE-type phenomena can occur in many circumstances, including fainting spells, serious disease and in the seconds before potentially catastrophic accidents, like falling off a cliff. While that doesn't suck the mystery from the phenomenon, it does suggest that NDEs are a flawed pointer to what might await us in death as opposed to the process of dying or a really hairy moment.
Another, possibly key, point is that NDEs vary across cultures. In a soon-to-be-published review of the literature, a team of Australian researchers reports, for example, that Chinese NDEs are dominated by feelings of bodily estrangement without all the pleasant stuff, and that the Japanese see caves rather than tunnels. For co-author Mahendra Perera, a Melbourne psychiatrist, these differences don't prove that NDEs are hallucinations, only that their "final expression is colored by culture, language and learning."
Science is trying to solidify the brain-based theory of NDEs, which goes something like this: Survival is our most powerful instinct. When the heart stops and oxygen is cut, the brain goes into all-out defense. Torrents of neurotransmitters are randomly generated, releasing countless fragmentary images and feelings from the memory-storing temporal lobes. Perhaps the life review is the brain frantically scanning its memory banks for a way out of this crisis. The images of a bright light and tunnel could be due to impairment at the rear and sides of the brain respectively, while the euphoria may be a neurochemical anti-panic mechanism triggered by extreme danger.
As for perhaps the strangest element of NDEs, the out-of-body experience, studies led by Swiss neuroscientist Olaf Blanke have shed light on what may be going on there. In 2002, Blanke and others reported how they were able to induce OBEs in an epilepsy patient by stimulating the brain's temporoparietal junction (TPJ), thought to play a role in self-perception. In emergencies where blood supply is cut, says Blanke, "the effects are occurring first at the TPJ, which is a classical watershed area of the brain." It's probable, he concludes, that stress in the TPJ causes the dissociation of NDEs — a dissociation that's entirely illusory.