The Search for Meaning in a Mysterious Brain Signal at Death

Research on a surge of gamma wave activity at death has been cited as proof your life flashes before your eyes before you die; in truth, no one knows exactly what it means.
Brain scans on a screen.
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In 2016, an 87-year-old man went to the emergency room at Vancouver General Hospital after falling down. A CT scan showed that his brain was bleeding, and he needed surgery. After the operation, the man was stable for two days, but then he started to decline and have seizures. 

Because of the seizures, his doctors measured the electrical signals from his brain using an electroencephalogram, or EEG. While the electrodes were on his head, the man had a heart attack and died. 


A study published at the end of February documented what was found during the recording: In the 30 seconds before and 30 seconds after the man’s heart stopped, there was a surge in brain activity—and not just any activity, but gamma waves. Brain oscillations, or waves, are patterns of coordinated brain activity; gamma waves are associated with conscious states, including learning and memory, and have also been observed in meditative states

Why would a man, as he was dying, have a sudden increase in a brain activity associated with consciousness? In the paper, the authors wrote that “it is intriguing to speculate that such activity could support a last ‘recall of life’ that may take place in the near-death state.” 

Though the authors included some important caveats, and though it is impossible to read subjective experience from an EEG, the case created a media sensation over the past couple of weeks, suggesting that what happened to one man with a brain injury provides evidence that we relive memories in the moments before we die. “A new study suggests our lives really do flash before our eyes in our final moments,” wrote The Daily Mail. MSN reported that this study “reveals what our last thoughts may be.” The Philly Voice wrote, “What happens when you die? Life may literally flash before your eyes.” Live Science reported, “First-ever scan of a dying human brain reveals life may actually 'flash before your eyes.’”


Could what was observed here be the neural signature of the near-death experience, or our lives flashing before our eyes as we die? It’s a provocative speculation, but that’s all it is: a speculation. It also wasn’t anything new. Though the authors of the new paper wrote that this was the “first-ever” continuous recording by EEG of a person as they died, this exact phenomenon has actually been noticed and published about for over a decade.

The past studies, in combination with this one, show there can be a surge of electrical activity in the brain right as people—or animals—die, which sometimes continues after the heart stops. It’s a topic that deserves investigation, because it could have important implications for end of life care, organ donation, or understanding the exact process of death. But what it means, and how it’s experienced, is still unknown. For now, what this finding might be most effective at teaching us is how data is filtered through our own personal beliefs: What people think of the surge often tells us less about a still-mysterious phenomenon than it does about their own worldviews. 

While the recent paper boasts about being “first”—and this was technically the first time the specific type of EEG measurement here was done—it’s not the first to measure the brain as someone died. 


“It is not the first continuous EEG recording from the human brain in the transition to death,” said Loretta Norton, a neuroscientist at King's University College at the University of Western Ontario. She published a paper on EEG measurements as people died in 2017; the main difference is that her study didn't have full-scap coverage of electrodes, as the new one does. There were a couple of other differences: In her patients, there was a decision to remove life-sustaining therapies, while the new paper, and another from 2021, cover  patients who died despite receiving treatment. 

This isn’t just about who was first to what: A case study like this, while intriguing on its own, is even more interesting when it’s considered in combination with evidence offered by past work that has shown the same unexpected surge in electrical activity in the dying brain. 

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Here’s what’s been observed in similar published papers over the past 13 years: In animals and in humans, at the time of cardiac death (when the heart has stopped and there is no pulse), a proportion of animals and humans show an increase in electrical activity in the brain. This is unexpected, said Lakhmir Chawla, a critical care doctor who has published numerous papers on this topic, because there’s no blood flow and no oxygen going to the brain.


In the intensive care unit (ICU), patient’s brains are sometimes measured with EEG monitors that record waves from the front of the head and algorithmically translate them into a number between zero and 100 to inform doctors about a person’s level of wakefulness. In some people, Chawla noticed that when their pulse went to zero, the number would momentarily shoot up right when they died. In 2009, Chawla and his colleagues published this observation: seven critically ill patients had life support withdrawn, and then there was a surge in electrical activity before the machine’s readings fell to zero. 

At first, Chawla thought it might be a seizure, or the brain releasing all its energy.  But after looking at the raw EEG data for one patient, Chawla and his colleagues found that the activity wasn’t seizure activity, or some last-gasp attempt of the brain to save itself.  They found that the signal was on a higher frequency that’s usually associated with gamma waves. This, too, was surprising. To see gamma wave activity, which is associated with consciousness, was “massively unexpected,” Chawla said. 

More work has continued to reveal this spike in gamma activity—but importantly, not in all patients. In 2017, Chawla and his colleagues observed 35 patients, seven of whom were clinically considered brain dead. None of the brain-dead patients showed an increase in brain activity at death; 13 of the 28 remaining ones did.


In Norton’s 2017 study, she and her colleagues measured EEG activity 30 minutes prior to death until 30 minutes after death in four patients. They, too, saw increases in higher-frequency brain waves similar to those described in the new paper in two of the four patients just before cardiac death, but didn’t see any gamma activity after death.  

Most recently, in 2021, a study looked at data from patients that died from heart attacks, who had also been undergoing standard EEG monitoring in an ICU. Of 19 patients who died a cardiac death, 11 had EEG activity following permanent cessation of the electrical or pump function of the heart, they reported. Jan Claassen, the senior author on that paper and a neurologist at Columbia University, said that they had one patient out of 19 who showed EEG activity briefly after blood flow to the brain stopped.

This has been seen in animals too. In a study from 2013, George Mashour, an anesthesiologist at the University of Michigan, and first author Jimo Borjigin looked for this brain activity in rats. They implanted electrodes into the brains of nine anesthetized rats, and then killed them. In the moment just after cardiac death, there was a surge of high-frequency brain activity. 

They found that the surge of electrical activity wasn’t just the brain going “haywire” before death, Mashour said. The brain activity was coordinated, and in a specific higher wave frequency: the gamma bandwidth. (A 2011 study that decapitated rats with a miniature guillotine—in order to assess how humane this method is for euthanization—also found that there was a “a very slow, large, late wave in the EEG,” the authors wrote.)


Mashour said that the new case report is interesting because it continues to connect the work done in rats to what’s been observed repeatedly in humans. “They were able to identify very similar findings, and these studies mutually complement and support one another,” he said. 

This part of the story is consistent, Chawla said: Some portion of people after cardiac death display cohesive gamma wave activity. Chawla gets phone calls from doctors all over the country who report the same. “I don’t think there’s anyone who can argue that this is not happening,” he said. 

Intriguing as all of this is, there’s still a huge gap between what exactly is going on from a phenomenological perspective, meaning how this surge is experienced. “I don’t know what the rat was experiencing, if it was experiencing anything, because in our study we had the animals anesthetized,” Mashour said. 

Similarly, we can’t know what the man in the newly published case report was feeling, or if he saw memories from his past. Chawla said that it can be a valid hypothesis that this brain activity is connected to a near-death experience (NDE), or reliving memories, given the timing and kind of brain activity. But proving that hypothesis, on the other hand, would be difficult.  

NDEs often have the same characteristics, and people remember them extremely vividly. In 1975, a doctor Raymond Moody collected reports of NDEs from 150 coma survivors, finding that NDEs can include out of body experiences, feelings of peacefulness, entering a gateway or tunnel, and seeing a bright light. But similar descriptions of near-death experiences have existed long before that, like in Hieronymus Bosch’s painting The Ascent of the Blessed from 1505. 


NDEs have been reported in 10 to 23 percent after recovery from heart attacks, but only in 3 percent of people who had recovered from traumatic brain injuries. Not all NDEs are enjoyable experiences: One study from 2019 found that 14 percent of them are “described as nightmarish.”

It could be that NDEs are related to this brain activity near death. But it’s one thing to observe this brain activity, Mashour said, and another to say that it is related to a specific kind of conscious experience. 

The authors of the new paper did discuss caveats: The man’s brain was severely injured, with bleeding, swelling, and seizures. The senior author, Ajmal Zemmer, told Motherboard he’s been trying to stress in press interviews that this was a single case study, that’s not necessarily generalizable. 

But the media coverage—and some of the quotes from Zemmer—took interpretation too far, according to the other scientists who have done work on this topic. “Something we may learn from this research is: although our loved ones have their eyes closed and are ready to leave us to rest, their brains may be replaying some of the nicest moments they experienced in their lives,” Zemmer told The Daily Mail. 

Actually, Norton said, we don’t know that’s the case. It is interesting that the brain activity that’s been observed is in the gamma frequency. But there should be caution when interpreting the gamma waves, because that frequency can overlap with other signals from the body, like electromyography signals that come from the muscles. 


It could also be picking up signals from non-physiological sources, like elements that are present in a busy intensive care unit. “An ICU is a very noisy environment,” Norton said. “It has a lot of equipment and machines in the environment and creates quite a lot of artifacts.”

Claassen agreed that in the critical care environment, the high gamma range signal detected on surface EEG should be interpreted with great caution. “These electrical signals are not unique to a highly specific neurological function like reliving your memories; they have moreover been seen broadly including in seizures,” he said. “Just because gamma surges may have been associated with a certain clinical or psychological phenomenon in one context does not mean that one can assume the psychological phenomenon is present any time gamma surges are detected.”

Norton said it’s possible that this activity could reflect a feature of neurological death, but whether or not it’s consciously experienced by the patient, she has doubts about. Again, not every person has this burst of activity, and it’s not known why. It could be due to brain injury, different medications, or some other variation in neurobiology. 

Patients in the ICU are often heavily sedated, for their comfort, which leads to unawareness. “The fact that somebody might have some kind of internal awareness and reflection, I think, is extremely unlikely,” she said. 


Mashour said he finds it striking that the brain activity does seem to be organized, but he cautions we have nothing to correlate this brain activity with an experience yet, and he doesn’t think we can say for certain it’s the neural substrate for the near-death experience. 

“It cannot be stated, ‘Well good news, don’t be afraid, you’re going to be living it all again in this blissful state of the near-death experience,” Mashour said. 

Investigating this brain activity further could lead to important and practical considerations about end of life care. Currently many people are sedated at the end of life for their own comfort. Would that prevent them from having this experience? We also often think of death as an off-on switch. This kind of brain activity, after the heart has stopped, challenges that assumption. 

“Doctors assume that after clinical death, the brain is dead and inactive,” Borjigin told science journalist Ed Yong in 2013. “They use the term ‘unconscious’ again and again. But death is a process. It’s not a black-or-white line.”

There could be implications for organ donation—how long should operators wait before harvesting organs, if there is, at times, this surge of activity right after cardiac death? Waiting too long can compromise the organs’ viability. 


Mashour wondered if it could be related to other phenomena, like terminal lucidity, which is when people have been observed to have enhanced cognition just before they die. For example, in Alzheimer’s patients, it can sometimes be the case that a person becomes lucid again, then dies shortly after. 

Zemmer said he’s looking to continue studying this, but that it’s a struggle to get the proper recordings. Given the nature of the work, he’ll almost certainly be confined to sick or injured patients, and it can be difficult to predict the time of death.

Mashour thinks that one way we could try to empirically connect this brain activity with NDEs is to study the near-death experience in people who aren’t dying. People who narrowly avoid an accident can have near-death experiences, sometimes called fear-death experiences. Some drugs, like DMT or ketamine, have been theorized to mimic or be similar to NDEs. 

Then, at least, there’s actually the opportunity for a person to describe what they experienced, and it could be correlated to neurophysiology. “We’re just not going to be able to answer this question by recording the whole-scalp EEG of every cardiac arrest,” Mashour said. 

Mashour and Norton’s past studies also got a lot of press. “It was on the front page of the Washington Post, as a rodent study,” Mashour said. 


When Norton’s paper came out in 2017, she didn’t do any media requests because the findings were too sensationalized, and the headlines didn’t reflect the content of what was in the paper. She worries the same thing is happening now. 

“They have no idea what that guy is experiencing,” Chawla said. It’d be different if the man survived, and reported that he experienced a recall of memories. But since he died, we have no idea what happened. To say otherwise, “is frankly appalling,” Chawla said. 

Zemmer said that he has been inundated with media requests from outlets from around the world. “If I could go to my patients or their family next time, or in a few years when this is solidified, and I could say, ’They’re okay, they're not suffering, they're not in pain, death is a natural part of life,” he said. “‘It is sad, but maybe they’re remembering the nicest memories of their life.’ Maybe that can comfort them. It’s a very, very difficult moment. To me personally, that is the biggest thing I take out of it.”

When asked by Motherboard whether it would be ethical to say that to someone if it potentially wasn’t true, Zemmer said, “I think that’s very fair and I very much respect that. I take a bit of a different standpoint, I think that you can see it either way. You could not say something that may not be true, or you can say something that may be true.” 

Chawla said that in the years he’s been publishing on this topic, he’s seen many different interpretations of the data. To some, this electrical surge is physical proof of the soul. “They are adamant that this is the soul rising from the body,” he said. In a talk from 2017, Chawla said that when he went on a radio show once, to explain these findings, he was “berated for not understand that the soul was clearly leaving the body and our stupid physicians are so scientific we have failed to see the divinity.” 

But for others with a less spiritual perspective, this brain activity becomes evidence to negate the spiritual experience—it shows that any near-death-like phenomenon is just a byproduct of the brain. We all have some kind of belief structure around death, whether it comes from contemplating your own death, or the deaths of those around you. A fascinating aspect of these data, and this topic in general, is how what people think the spike means often depends on their starting beliefs. 

This is probably true of all information that we receive: Our biases and belief structures influence our reactions and interpretations in some way. But this topic, in particular, seems to be an apt example of that.

“Having been through this so many times, whatever your belief structure is, if you wrote it down on a piece of paper before I showed you this data, I could predict with a high degree of certainty what you’ll think of it,” Chawla said. “It's an interesting notion about this data, but also about data in general.”

It makes sense for there to be fascination around this topic. “We all die, and we’re all trying to understand what happens to a loved one, or what happens to one's body during the dying process,” Norton said.

But because we care so much, it’s all the more reason for scientists to present their data without conclusions they can’t yet verify, Chawla said. “There is a singular right way to do this,” he said. “It’s very ethically tight: We describe without conclusion. Other people can conclude, but we, as scientists should be saying, this is what the data show.”

Follow Shayla Love on Twitter.