Undergoing a brush with death may sound terrifying. But people who have had a near-death experience (NDE) typically report feeling peace, comfort, and calm throughout the ordeal.
Perhaps it's the brain's way of coming to terms with its mortality. Or perhaps something more complex is going on.
Scientists have several theories to explain some of the surprising sensations associated with NDEs, such as physiological changes in the brain as brain cells die.
But a lot about NDEs remains a mystery, in part, because it's practically impossible to study in real-time, said Dr. Bruce Greyson, a professor of psychiatry and neurobehavioral sciences at the University of Virginia and co-founder of the International Association of Near-Death Studies.
Researchers must rely on anecdotes, memory recall, and in some cases, animal studies to understand how brains change from a NDE and what it could mean for future medicine.
What a near-death experience feels like
When it comes to describing NDEs, there are two sides to the coin: what's physically happening to you versus what you're perceiving on a psychological level.
Physically, NDEs are typically associated with extremely painful events, including a head injury, heart attack, or respiratory arrest.
But psychologically, the brain tends to shut down the sensation of pain – or at least the memory of it.
For example, Julia Nicholson – a former CEO, executive leadership expert, and business consultant – said that she saw the faces of her loved ones vividly flash before her eyes, one by one, during a near-fatal car crash in 1980.
"I don't remember feeling any pain until I arrived at the hospital," she recently told Newsweek.
Seeing loved ones – deceased or living – is common among NDEs, as is seeing a bright light at the end of a tunnel.
Other people have reported more corporeal sensations like that of leaving their body, floating above it, feeling physically drawn into that tunnel with the light at the end of it, or having a spiritual encounter with a supreme being, aliens, or lost loved ones.
And all the while, during these other-worldly experiences, people rarely report having felt fear or pain – it's usually an overwhelming sense of calm and love.
Some of these phenomena can't be explained by science – at least not yet. But in 2022 the NDE research community received something it had never witnessed before: the brain scan of a dying man.
And it unveiled some secrets that, up to that point, scientists could only speculate.
The brain scan of a dying man
In 2016, a then-87-year-old man was connected to an electroencephalogram, or EEG, when he unexpectedly had a heart attack and died. Researchers later published the results in Frontiers of Aging Neuroscience.
An EEG measures electrical signals that the brain produces in order to help diagnose or examine certain neurological conditions like seizures and memory loss.
Sure enough, doctors were monitoring the man for a series of recent seizures when his heart suddenly stopped beating.
In the paper, researchers reported that during the 15 seconds leading up to the man's heart attack, the EEG scan revealed high-frequency brainwaves called gamma oscillations, which are thought to play a role in creating and retrieving memories.
"It is very hard to make claims with one case… but what we can claim is that we have signals just before death and just after the heart stops like those that happen in the healthy human when they dream or memorize or meditate," lead study author Dr. Ajmal Zemmar told Insider's Anna Medaris.
Of course, these scans are of a man seconds before death and not exactly equivalent to an NDE, where the person survives. However, such activity may help explain why people see memory flashbacks or faces of people they know during an NDE, Greyson said.
Moreover, EEG scans of people attempting to remember their NDE also provide more clues to what an NDE does to the human brain.
What a near-death experience does to the brain
When people recall an NDE, the brain "shows increased activity in many different parts," Greyson said, "such as those associated with memory, vision, hearing, and emotion."
In particular, the temporal lobe, which is responsible for helping process sound and encode memories, is thought to be associated with out-of-body experiences and memory flashbacks during NDEs, said Dr. David San Filippo, an associate professor at National Louis University and a near-death experience researcher.
"That has led some people to believe that near-death experiences are simply biological, chemical reactions to the brain dying," San Filippo said.
To that point, a study in rats suggested that the overwhelmingly positive experience people report with NDEs may be linked to a flood of serotonin the brain releases. This may be the brain's way of gradually preparing the body for death by inducing feelings of euphoria and pain relief, San Filippo said.
While animal studies can offer clues, they're not an analog to what may be happening in a human and therefore more research is warranted on this topic, Greyson said.
Some researchers think NDEs are just as much spiritual as they might be biological.
Across different age groups and among people in different countries, reports of NDEs are strikingly similar, especially in regards to encountering a spiritual deity or feeling part of something bigger than life on earth, San Filippo said.
"We hear the same story. It might differ based on cultural or spiritual beliefs, but it is essentially the same," San Filippo said. "That leads us to believe that a near-death experience is a transpersonal experience happening outside of the brain."
What this means for future treatment
While researching NDEs is a challenge because they're hard to predict, as researchers come to better understand these phenomena, it could inform new therapies and treatments for people facing terminal illnesses, and their loved ones.
For example, San Filippo said that people in his studies who have had an NDE and recall feeling calm and comforted during the experience report that they no longer fear death.
"If we can learn more about what causes a positive near-death experience that is comfortable and peaceful, we could possibly develop a powerful therapy for people who are in turmoil or struggling," Rasouli said.
Rasouli added that it could make the concepts of death and dying "become less mysterious and subsequently, less frightening" for us all.
"I think people benefit from hearing stories of NDEs and are comforted by the idea that death is a process and the pain ends," San Filippo said.
This article was originally published by Business Insider.
More from Business Insider: