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Does Your Brain Know When You’re Dead?

Medically Reviewed by Hansa D. Bhargava, MD on November 08, 2017
arena tunnel

Nov. 8, 2017 -- When you die, your brain may know it.

Researchers say that after your heart stops, your brain  stops working as well. If your brain has shut down, how is that possible?

But many people who have been resuscitated and, essentially, brought back to life -- describe experiences that occurred after death. If your brain is dead, how is that possible?

“Since the 1960s, when CPR was developed and we began to be able to resuscitate people whose hearts had stopped, many of them have reported these unusual experiences in which they had full awareness, consciousness, of events going on at the time of their cardiac arrest,” says Sam Parnia, MD, PhD, director of critical care and resuscitation research at NYU Langone Health in New York City. “In many cases, those have been verified by medical and nursing staff.”

Each year, as many as 1 out of 5 people whose hearts stop will be revived. The stories that some of them share are often called near-death experiences, or NDEs. These incidents often feature tunnels leading to a bright light, spiritual encounters, meetings with deceased loved ones, and other things that seem mystical. In some cases, people whose hearts have stopped beating describe out-of-body experiences, in which they feel like they’ve left their bodies and seen the efforts to revive them.

“These are anecdotal reports, but there are a large number of them going back decades, and these testimonies suggest that something is going on,” says Parnia.

When the brain stops, blood quickly stops flowing to the brain. Patients are unconscious, and their brains register no activity. They are, says Parnia, clinically dead.

“In the context of cardiac arrest, they are not near death,” says Parnia. “They really have gone biologically beyond death.”

Previous Studies Offer Clues

Though unable to explain how patients in this state can have such vivid experiences, some research supports their claims. In a 2014 study, Parnia and his colleagues interviewed 101 people who had been revived after cardiac arrest. Nine had had an NDE, while two of the patients were able to describe events happening while doctors attempted to resuscitate them. One of those patients, the researchers verified, accurately recalled events that occurred minutes after cardiac arrest. That should not be possible.

“We can’t explain consciousness occurring during cardiac arrest,” says Parnia. “What happens at cardiac arrest is you have no blood flow into your brain, and your brain shuts down immediately.”

Earlier studies also examined this phenomenon:

  • A 2000 study by Parnia, also in Resuscitation, reported that seven cardiac arrest survivors out of 63 interviewed described memories similar to an NDE.
  • In 2001, researchers in the Netherlands reported that 41 of their 344 study participants, who had each had a cardiac arrest, had an NDE. The study appeared in The Lancet.
  • Researchers at the University of Virginia found that NDEs happened in 11 of the 116 cardiac arrest patients who took part in their 2003 study, published in General Hospital Psychiatry.

The author of that last study -- Bruce Greyson, MD -- developed the tool used to establish NDEs. The Greyson scale lists 16 things common to NDEs. Patients must meet certain criteria, which include:

  • A changed sense of time
  • Faster-than-normal thoughts
  • Feelings of peace and joy
  • Feelings of being separated from the body
  • A sense of being in a different, unearthly place
  • An encounter with a spirit, such as a deceased relative or divine being

Neurologist Kevin Nelson, MD, also investigates near-death experiences. His research has led him to conclude that people who have had NDEs have brains that are more likely to blend waking consciousness with REM consciousness, the phase of sleep when dreaming happens.

“Many out-of-body experiences can be explained by triggering REM consciousness,” says Nelson, a professor of neurology at the University of Kentucky and author of The Spiritual Doorway in the Brain: A Neurologist's Search for the God Experience.

Absolute Truth Is Elusive

Nelson says these can be powerful, sometimes life-changing events for patients, but he's skeptical that they happen when the brain has completely shut down. He points out that electroencephalograms (EEGs), which monitor brain activity, can be very difficult to interpret during resuscitation.

The chaos of an emergency room can make it difficult to pinpoint when the heart or brain might stop working. People are scrambling around; equipment gets bumped, which can throw off later analysis.

“Wires get jiggled, signals cross,” he says. “We don’t know if the EEG is actually flatlined, and, if it is, we don’t know that the conscious experience takes place during the flat line. People are not having experiences when there’s a true flatline EEG.”

Parnia’s research, however, does not support that conclusion.

“In our study, we had confirmed consciousness present for at least 3-5 minutes,” he says. "It’s a paradox. The fact that you have people who can fully recall something, who appear to have full consciousness, when the brain is shut down, suggests that consciousness may be a separate entity from the brain."

Some parts of the experience may be easier to explain, Nelson says. He explains that the sense of seeing a tunnel with a bright light at the end, for example, comes from the lack of blood flow to brain. It happens when a patient’s vision narrows so that it resembles a tunnel. The light may simply be the last thing the eyes are capable of seeing before unconsciousness sets in.

Lasting Changes

How such experiences happen may be less important than the impact that they have, says Laurin Bellg, MD, a critical care doctor at ThedaCare Health System in Appleton, WI.

Often, people who have had an NDE say they no longer fear death. They feel less caught up in everyday worries and cares, and they have a new or heightened sense of altruism, or selfless concern for others.

“It’s worth paying attention to the fact that people who have had these experiences are changed, and universally so,” says Bellg, who interviewed many such people for her book Near Death in the ICU:  Stories from Patients Near Death and Why We Should Listen to Them. “Many of the people that I talked to felt they were in a place they called heaven or the afterlife. In many cases, they were disappointed that they had to come back.”

Nelson agrees that the cause of NDEs may be less significant than what he calls the “personal and transformative value” they have for patients. But, like Bellg, he says these events should not be taken as evidence of an afterlife.

“I hope there is an afterlife; don’t get me wrong, I’m not disparaging that faith at all. But the idea that these experiences prove a great beyond is not true,” says Nelson.

Still, it's tough to find a good explanation for these events. For example, they don't come from delirium or hallucinations that can happen while under anesthesia, says Bellg.

“Those tend to be scattered images that patients can’t fit together with any coherence,” she says. “Patients describe NDEs with such clarity.”

And Parnia suggests that some NDEs may be even richer and broader than patients recall. Cardiac arrest can cause the brain to suffer memory problems, and parts of the experience could be lost as a result.

In addition to his research into near-death experiences, Parnia also investigates how to improve resuscitation so that patients can be revived without brain damage. As those methods get better, and more people survive cardiac arrest with their brains intact, the numbers of reported NDEs may rise.

Bellg says their stories may help dying patients face their own deaths.

“For patients who are afraid of dying, it can be very useful to tell them that most of those who have been through death found it peaceful,” she says. “People who have died and come back did not find it frightening at all and look forward to going there again. It has been useful to me in my practice to say I’m not so sure that there’s anything to fear, and I’ve found that that offers comfort.”

Show Sources

Laurin Bellg, MD, critical care doctor, ThedaCare Health System, Appleton, WI.

Kevin Nelson, MD, professor of neurology, University of Kentucky, Lexington.

Sam Parnia, MD, PhD, director of critical care and resuscitation research, NYU Langone Health, New York City.

Greyson, B. General Hospital Psychiatry, July 2003.

International Association for Near Death Studies: “Greyson NDE Scale.”

Nelson, K. Annals of the New York Academy of Sciences, November 2014.

Parnia, S. Resuscitation, December 2014.

Sinha, N. Current Neurology and Neuroscience Reports, July 1, 2017.

Van Lommel, P. The Lancet, December 15, 2001.

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