WASHINGTON POST: When patients see the line between life and death, should we believe them?

As she was lifted into the ambulance and Miasha Gilliam-El told herself, “I can’t die this way.”

After emergency workers at the hospital cut the clothes off her to assess her breathing, the 37-year-old nurse and mother of six, blacked out.

What happened next has happened to thousands who’ve returned from the precipice of death with stories of strange visions and journeys that challenge what we know of science. Last year, researchers from Belgium, the US and Denmark launched an effort to explain NDEs (near-death experiences) on a neurobiological level — work that is now being contested by researchers in Virginia.

At stake are questions almost as old as humanity, concerning the possibility of an afterlife and the nature of scientific evidence — questions likely to take centre stage at a conference of brain experts in Porto, Portugal, in April.

“The next thing I knew, I was out of my body, above myself, looking at them work on me, doing chest compressions,” Ms Gilliam-El said, recalling the day in 2012 when she suffered a rare condition called peripartum cardiomyopathy. Between the last month of pregnancy and five months after childbirth, a woman’s cardiac muscle weakens and enlarges, creating a risk of heart failure.

Ms Gilliam-El, who had given birth just three days earlier, recalled watching a doctor try to snake a tube down her throat. She remembered staring at the machine showing the electrical activity in her heart and seeing herself flatline. Her breathing stopped.

“And then it was kind of like I was transitioned to another place. I was kind of sucked back into a tunnel,” she said. “It is so peaceful in this tunnel. And I’m just walking and I’m holding someone’s hand. And all I’m hearing is the scripture, ‘Yea, though I walk through the valley of the shadow of death …’”

While neuroscientists have discovered more and more about the inner workings of the brain in recent decades, a deep mystery still surrounds NDEs like Ms Gilliam-El’s.

Writing last year in the journal Nature Reviews Neurology, a research team led by Charlotte Martial, a neuroscientist at the University of Liege in Belgium, synthesised some 300 scientific papers focusing on commonalities across these experiences: viewing one’s body from the outside, journeying through a tunnel towards a brilliant light, and experiencing a deep sense of peace. The authors linked these experiences to specific changes in the brain, creating a model called NEPTUNE (short for neurophysiological evolutionary psychological theory understanding near-death experience).

Bruce Greyson and Marieta Pehlivanova, researchers at the University of Virginia School of Medicine, responded with a sweeping critique of the NEPTUNE model in the journal Psychology of Consciousness: Theory, Research and Practice.

While calling the model “an admirable strategy”, they wrote that aspects of such experiences cannot be explained solely by brain physiology, and they criticised the NEPTUNE authors for omitting evidence that did not support their ideas.

Although this debate is taking place in the rarefied atmosphere of scientific journals and conferences, it is almost certainly one that has crossed the minds of most people.

“This is not the digestive function of some lower life form we’re talking about here. These are implications that reach all of humanity,” said Jeffrey Long, a radiation oncologist and co-author of Evidence Of The Afterlife: The Science Of Near-Death Experiences.

“Do we have some evidence?” he asked. “And how strong is that evidence that we have life after death, that our consciousness survives bodily death?” Dr Long — who was not involved in the paper or the critique — said he has studied more than 4000 NDEs.

The NEPTUNE researchers cited several studies showing that about 10 to 23 per cent of near-death experiences occur after a heart attack, 15 per cent after a prolonged stay in intensive care and 3 per cent after a traumatic brain injury. Others occur after electrocution, near-drowning and complications during childbirth.

“For most of them, it’s a life-transforming experience,” Dr Martial said. “Typically, they are less afraid to die (afterwards).” They tend to develop greater interest in spirituality and can become more empathetic, she said.

To create the NEPTUNE model, scientists examined changes in gas concentrations in blood vessels in the brain: the decreased oxygen and increased carbon dioxide that occur just before and during a cardiac arrest.

They cited studies suggesting that the sensations may be generated in the temporoparietal junction, a high-level hub for processing sensory information and helping distinguish the self from others. Studies indicate that applying electric stimulation to this area, behind and just above the ear, could trigger an out-of-body experience, they wrote.

Folded into their analysis were observations about brain chemistry, including the nerve cells and chemical messengers that regulate mood, sleep and learning. Dr Martial said the model is intended as a living document that can be revised as scientists learn more.

But Dr Greyson and Dr Pehlivanova disputed key aspects of the model. They wrote that illusions triggered by stimulation are “nothing like the visions of deceased persons reported”. For example, one study reported inducing an illusion in which a patient felt the presence of a person behind them whom they could not see or hear.

“This is not remotely comparable to the visions reported in many (near-death experiences?) of identified deceased persons who are seen, heard, smelled, and touched,” wrote Dr Greyson and Dr Pehlivanova, who are, respectively, a professor emeritus and a research assistant professor of psychiatry and neurobehavioural sciences.

The two acknowledged that NDEs “are typically triggered by physiological events” but stressed that such events do not account fully for the experiences people have described. They faulted the paper’s authors for dismissing evidence from patient accounts and from hospital staff who have supported aspects of those accounts — for example, the number of people who were in the room during resuscitation.

Scientists disagree on whether the stories patients tell constitute reliable scientific data.

NDEs have been described since antiquity. Researchers have been collecting and discussing accounts since at least 1892, when Swiss mountaineer and geologist Albert Heim discussed stories he’d collected since his own brush with death while climbing in the Alps.

By their nature, these reports can be difficult to define and even harder to analyse with scientific rigour.

In a 1983 paper, Dr Greyson described a 16-item scale he developed for measuring accounts of NDEs and standardising research into them.

But the effort to impose rigour on the study of NDEs forces researchers into an uncomfortable zone that straddles the line between the scientific and the spiritual.

“These stories are seductively powerful narratives that give hope to our deepest yearnings for consciousness beyond our death,” Kevin Nelson, an emeritus professor of neurology at the University of Kentucky, wrote in an email.

I too have such hope, but with wax in my ears and science lashing me to the mast, I will not succumb to the siren’s song.

(Nelson was one of the NEPTUNE paper’s authors).

Dr Greyson said the NEPTUNE researchers may dismiss the testimony of patients “as not evidential, but the fact is that every scientific discovery begins with subjective observation that may eventually be corroborated by controlled experiment”.

In addition to testing aspects of the NEPTUNE model, Dr Greyson and Dr Pehlivanova wrote that “it will also be important to remain open to other potential causes, whether currently unknown or not yet fully understood”.

By necessity, most previous studies have involved researchers going back to patients after their NDE to gather their accounts and medical records. But such retrospective studies are open to biases in how people remember events after time has passed and how they have told their story to others.

However, NEPTUNE researcher Dr Martial, said that she and three colleagues are in the midst of a prospective study that will track patients from the moment they are taken to a hospital’s resus room. It will involve video recorded at the hospital and recordings of electrical activity in the brain.

“When we die, this is a process — not just an event,” Dr Martial said. “During a cardiac arrest, we have a decrease of oxygen, which leads to a decrease of brain activity. But at some point, actually, we see an increase of electrical brain activity, and then we can observe a kind of flatline.”

Ms Gilliam-El remembers that her NDE ended when a powerful voice told her “not yet” and she felt herself return to her body. Everything looked blurry in the bright hospital room.

She feared that if she told anyone what had happened, they wouldn’t believe her.