In the 1960s, while filming Cleopatra, the actress Elizabeth Taylor developed such a severe case of pneumonia that she fell into a coma and was pronounced dead by doctors, according to her own account on The Oprah Winfrey Show. While Taylor was in a nonresponsive state, she apparently had a near-death experience. She remembered seeing the doctors working on her in the operating room, and saying they thought they had “lost” her. She remembered a brief reunion with her ex-husband and producer Mike Todd, who had passed away a few years earlier. She remembered Todd telling her it wasn’t yet her time. When she eventually recovered from the coma and the pneumonia, she had lost her fear of death, she told Winfrey.
Taylor’s experience has some of the classic features of a near-death experience, or NDE, a term first coined in 1975 by psychiatrist, philosopher, and researcher Rick Moody, who had one himself. There are now hundreds of such accounts in the research literature, and yet they remain among the most mysterious phenomena known to neuroscience. This is partly because much of what scientists do know about them comes from subjective self-reports from survivors long after the experience is over. But as resuscitation science has improved, more people are surviving life-threatening events, such as comas and cardiac arrest, which is changing the tools we have to plumb their depths.
One Belgian researcher named Charlotte Martial, from the University of Liege, recently completed the first EEG recordings of patients in the throes of near-death experiences and helped to develop a neurophysiological model that she says can explain how they arise and why they might have evolved. I talked with Martial, who has been studying near-death experiences for over a decade, about how NDE memories shift over time, the possible adaptive value of NDEs for humans, and what mysteries remain.
What is the definition of the near-death experience?
There is still no universally accepted definition in research. But I like to define the phenomenon as an episode of disconnected consciousness, a mental experience that has no connection to one’s surroundings or environment, but with prototypical features such as the out-of-body experience, meeting entities, seeing a bright light, and having an intense feeling of peacefulness. And this happens when we’re close to death or when we believe we’re close to death.
Do near-death experiences challenge traditional models of consciousness?
My personal view is that they don’t challenge what we know about physiology. My team took two years to review the entire literature on consciousness, everything related to near-death experiences, the dying brain, and created the first comprehensive model that gathers psychological, but also neurophysiological data, to convincingly explain how this complex, intense experience arises during a severe physiological crisis. But we need to empirically test several parts of the hypothesis.
Historically, NDEs have been used to exemplify that we don’t understand what happens when we’re close to death. That’s partly true: There are many remaining questions about what we subjectively experience when we’re close to death. But we have some answers, too. According to our model, when we’re close to death, the brain is deprived of oxygen, which creates a lack of energy in the brain cells, triggering a chain reaction of several neurochemical mechanisms, including the massive release of specific neurotransmitters such as noradrenaline and serotonin. This release of neurotransmitters occurs in specific parts of the brain, such as the temporal parietal and occipital regions, which we’ve shown to be much more active during this physiological crisis, and which are specifically associated with consciousness, perception, and memory.
What this demonstrates is that we don’t need our entire brain to be conscious. We just need some specific parts of the brain that are functionally activated, permitting this rich experience to arise.
You’ve suggested that the NDE serves an adaptive function in extreme situations like threat or collapse. Can you tell me more about this?
We suggest that something called thanatosis, where animals pretend to be dead to protect against predators, may have been a kind of precursor in evolution. With the evolution of complex brain and language in humans, this stereotypical behavior evolved into the more complex and multi-dimensional experience that is the NDE. Basically, we suggest the NDE is a defense mechanism for coping with a life-threatening situation. It permits the person to disconnect from the environment, from the surroundings, to be absorbed into a more peaceful mental experience.
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Wouldn’t such a disconnect make it more difficult to escape the life-threatening situation?
We suggest it’s like a biological reflex that arises in the brain when we’re close to death. We also suggest that NDEs could, for some at least, have psychological benefits. A lot of people who experience NDEs say it’s life transforming. It allows them to evolve and change their own behavior or beliefs.
But would there be situations where it wouldn’t be so adaptive? Say you’re in an avalanche and you need to escape—wouldn’t you need to be conscious and finding solutions?
We suggest that the NDE arises when you don’t have any other kind of escape. So there is this fight-or-flight mechanism, but when neither fight nor flight is possible, this alternative would arise.
What about people who have negative near-death experiences—how do these square with evolutionary explanations?
Yes, usually, we talk about the positive near-death experience, but there are also some very distressing ones, where people are in a hellish world, with fire and monsters everywhere. Afterward, we can see that those patients may have PTSD [post-traumatic stress disorder]. This is one of the most intriguing experiences, which has so far been understudied. There are fewer than 10 scientific papers on it. We’re still thinking about that in the context of the evolutionary hypothesis.
There are at least two possible explanations. One, maybe some neurotransmitter can explain some part of it. So maybe these patients don’t experience the massive release of endorphins, which trigger the intense feelings of peacefulness and calmness. And two, people with negative NDEs are more likely to attempt to die by suicide, compared to those who have positive NDEs. This may reflect something about the mindset of these individuals when the life-threatening situation arose.
From what you’ve found in your studies, does it seem that some people are more susceptible to near-death experiences than others?
So far what we observe in my study, but also in the work of other researchers, is that at least one trait seems to be consistent in those patients who report NDEs, and that’s a propensity for dissociation in everyday life. Not pathological states of dissociation, like the kind seen in PTSD or borderline personality disorder, but rather a capacity to be connected with internal states and disconnected from the environment.
You recently made the first EEG recordings of people undergoing near-death experiences. What did you find?
It’s not published yet, but we conducted a prospective two-year study in a hospital where as soon as the patient was transferred to the resuscitation room of our hospital, we ran in to hook them up to EEG, or electroencephalogram. We tracked 180 patients, and of those, 12 had near-death experiences. Our preliminary results suggest that the brains of patients who had near-death experiences showed greater complexity than those who did not. [Brain complexity is a marker of the brain’s ability to adapt, process information, and maintain integrated, flexible, and efficient neuronal network activity.]
When we’re unconscious, like in a coma or dreaming, brain complexity measures tend to be super low, well below what they are when you’re conscious and awake. When you take a psychedelic, your brain complexity is much higher than when you’re awake. But those unresponsive patients who later report NDEs show higher brain complexity than the wakeful patient.
What’s the one mystery about near-death experiences that you’re most excited about resolving?
Some features of NDEs are still difficult to explain, such as precognition. Some people seem to report future events that are later confirmed. But so far, this hasn’t been properly tested. There is also a big question about the temporality of the experience. Our hypothesis is that NDEs happen just before or just after the cardiac arrest, where you can see a peak of activity. This is something that’s been observed in a study of rats in cardiac arrest. But it’s not super clear when the NDE happens.
How NDE memories evolve is also not clear. Something like 98 percent of the empirical literature in the field is retrospective, meaning that most of the studies are done in patients who experienced the NDE years or decades prior. There are only a few studies that are done in real time, like the one that we completed. Again, we haven’t published this study yet, but what we observed is that as soon as several days after the acute severe crisis, we can see memory change in terms of content of the experience, which challenged what was found in the retrospective literature.
Some features appeared, and some others disappeared in their memories. For instance, you can have someone who doesn’t report an out-of-body experience upon awakening, however, two months later, the person does report it.
It’s a new finding, but isn’t that surprising because we know that human memory is malleable. It makes sense that memory would take some time to be properly coded in people who have been in a severe physiological crisis, where sensory input and output are disturbed.
Is it fair to say that some of the contents of the near-death experience are a kind of illusion?
It depends how you define illusion. When you meet entities or when you feel as though you’re out of your body, those are non-ordinary states of consciousness caused by disturbed perception. So you don’t actually meet your father in a tunnel of light, for example. But near-death experiences are real in the sense that the person who reported it did have this vivid and intense subjective experience. 
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