Have you or someone you know ever had a near-death experience (NDE)? These events are estimated to occur in as many as 10 to 20 percent of cardiac arrest survivors, who report seeing white lights, voices, or even visits from loved ones who have already died.
Even though these experiences are more common than you might think, what causes these perceptions has remained a mystery.
Now, a new study published on May 1, 2023, in the Proceedings of the National Academy of Science provides “the strongest evidence yet” that some kind of covert consciousness remains for a short time after a person’s heart stops beating and they are considered dead, says lead author Jimo Borjigin, PhD, an associate professor in the department of molecular and integrative physiology and the department of neurology at the University of Michigan Medical School in Ann Arbor.
Covert consciousness is the state in which the brain shows inner signs of awareness and activity when evaluated with an EEG, even though the body is nonresponsive. It’s estimated that as many as 15 to 20 percent of people who appear to be in a coma show signs of covert consciousness, according to Scientific American.
Because many near-death experiences have common elements, it begs the question of whether there is something fundamentally real underpinning them, according to the authors.
Although most of us wonder what happens when we die, surprisingly little is known, says Dr. Borjigin. “When I first began studying the brain over a decade ago, I was shocked to find out we know so little about the entire process — what is happening to the heart, brain, and lungs to a person when they are dying,” says Borjigin.
Brain Waves and Memory
The study by Borjigin and her team is a follow-up to animal studies conducted almost 10 years ago in collaboration with George Mashour, MD, PhD, the founding director of the Michigan Center for Consciousness Science.
In that study, researchers analyzed the recordings of brain activity called electroencephalograms (EEGs) from nine anesthetized rats undergoing experimentally induced cardiac arrest.
Within the first 30 seconds after cardiac arrest, all the rats displayed a short but widespread surge of highly synchronized brain activity, including a type of activity called gamma waves.
But why is that significant? “We have brain waves going on in our brain all the time — they don’t stop. The question is: When do they increase and when do they happen? How can we correlate them with certain behaviors that we do,” says Ajmal Zemmar, MD, PhD, a neurosurgeon and researcher in death and near-death experiences at University of Louisville Health in Kentucky, who was not involved in this study.
One connection that brain researchers have made is with gamma waves, says Dr. Zemmar. “If someone were to put an EEG on our head and show us pictures and videos of memorable events of our lives — such as the birth of a child, a wedding day, a day somebody that we loved passed away — and we recall those events, gamma waves go up. So people believe that the presence of increased gamma waves activity is the way for the brain to recall memory,” he says.
After this activity was observed in rats, the next step was to find out if this could be happening across species — not just in rats, but in humans, too.
Last year, Zemmar led a group of researchers that showed that these gamma waves were coming a few seconds after the heart stopped beating in a human, confirming what was found in the rats, according to the findings published in Frontiers in Aging Neuroscience in February 2022.
Evidence That Death Might Not Occur After the Heart Stops Beating
“People always think when the heart stops beating, we’re dead. This is what we see in movies, when the EKG sign goes flat. What this research opens is: Maybe we’re not [dead yet]? Because the brain pulls off pretty coordinated activity after the heart stops,” says Zemmar.
This new study by Borjigin confirms those two previous studies: that the gamma waves are going up after the heart stops, and it further illuminates what that activity could mean, he says.
In the newest study, researchers studied four patients who died due to cardiac arrest in the neurointensive unit while under EEG monitoring at Michigan Medicine. All four of the patients were comatose, unresponsive, and ultimately determined to be beyond medical help. With their families’ permission, they were removed from life support.
Upon removal of ventilator support, two of the patients showed an increase in heart rate along with a surge of gamma wave activity. The other two patients didn’t show increases in either area.
Activity Detected in the Part of Brain Correlated With Religion and God
In the patients who did have activity, researchers also detected gamma waves in the so-called “hot zone” of neural correlates of consciousness in the brain: the junction between the temporal, parietal, and occipital lobes in the back of the brain, called the temporal parietal junction (TPJ). This area has been correlated with dreaming, visual hallucinations in epilepsy, and altered states of consciousness in other brain studies, according to the authors.
Previous research has shown that when someone has an out-of-body experience, there’s activity in the TPJ, says Zemmar. “Across cultures and religions, when people think of God or have religious or spiritual experiences, activity in that area goes up,” he says.
This is the first study to show that not only are gamma waves increasing when the heart stops, but that they are also located in the temporal parietal junction, which makes a lot of sense, says Zemmar.
These findings provide good evidence that near-death experiences are a product of the brain, says Borjigin. “The brain is dying. The owner of the brain is dying. When oxygen is so precious during the dying process, why would the brain have gamma activity? What is the function of these subjective experiences? Does it benefit survival for the subject? These are long-term questions we still need to answer,” she says.
Because this study only included four people, it’s too soon to make any global statements about what these findings mean, wrote the authors. They also noted that it’s impossible to know in this study what the patients experienced, because they did not survive.
Overall, this study is an important addition to the field, says Zemmar. “It’s a very difficult field to research, because getting the data is so hard. You can’t predict when somebody is going to die, and you can’t just apply an EEG on their head when they die to record this activity,” he says.
Larger studies at different centers, including EEG-monitored ICU patients who survive cardiac arrest, could provide much more information to further clarify whether these bursts in gamma activity are evidence of hidden consciousness even near death, said the authors.
Research Could Have Implications for End-of-Life Care and Organ Donation
There is an obvious societal interest in when death occurs and what we experience, but there are additional implications beyond that, says Zemmar.
“Being a neurosurgeon, it matters for us to decide what determines if a person is dead, and [if] we need to change how we currently define that,” he says.
Right now, we think if the heart stops beating or a person has stopped breathing, that person has died, says Zemmar. “If we only live 20 seconds after our heart stops beating, maybe in clinical sense, that doesn’t really make a difference. But there are researchers in Italy that recorded the brain of a monkey after the monkey underwent cardiac arrest, and the monkey exhibited this wave activity for two hours after their heart stopped," he points out. Zemmar was referring to experiments conducted in the 1960s, according to The New York Times.
“When has the patient stopped ‘being there’? How long after the heart stops, does the patient consciously continue? These questions have direct implications for things like organ donation and end-of-life care,” says Zemmar.