What is going on in your brain when you are about to die?


What happens when we actually die—the heart stops beating and the brain waves flatten?

Humanity has been searching for the answer to this question since ancient times. But it's difficult because the dead often can't tell us back about their experiences. Although religious texts offer a variety of explanations, scientists have struggled to find answers of their own, and they have made some progress in understanding the brain's transition from life to death.

Recently, a study monitored the brains of people near death, and some of them were able to recall their experiences on the verge of death. During cardiopulmonary resuscitation, some cardiac arrest patients' flat electroencephalograms suddenly become active -- even after their hearts have stopped beating for up to an hour, according to findings published Sept. 14 in the journal Resuscitation. A small number of surviving study participants were able to recall the experience, and one patient was able to identify a recording played as doctors resuscitated him.

The researchers interpreted the brain recordings from these patients as signs of "recollection of the death experience" - "something that has never been observed before," said Sam Parnia, the paper's lead author. Ya is an associate professor of medicine at New York University Langone Health Center. He has long studied the human death process. "We have also been able to propose a coherent, mechanistic explanation for why this occurs," he said.

To be precise, Parnia prefers the term "recalled experiences of death" rather than "near-death experiences," a term that appears in historical records from different cultures. There are reports. Some Western scientists previously dismissed these experiences as hallucinations or dreams, but recently some research teams have begun to take these phenomena more seriously as a means of studying consciousness and revealing death.

In the new study, Parnia and his colleagues sought to identify biological markers of recall of death experiences. Working with 25 hospitals, mainly in the United States and the United Kingdom, medical staff used lightweight equipment to measure brain oxygen levels and electrical activity in patients undergoing emergency heart attacks without interfering with treatment. The researchers also tested the patients' conscious and unconscious perceptions: They put on headphones and repeatedly played the names of three fruits: "banana," "pear" and "apple." Parnia explains that a person may not remember hearing the names of these fruits, but may still give the correct answer when asked to "randomly think of three fruits," which is unconscious learning. Past research has shown that even people in a deep coma can unconsciously remember the name of a fruit or city that someone else whispered in their ear.

Between May 2017 and March 2020, 567 patients suffered cardiac arrest at hospitals collaborating with the researchers. Medical staff collected data on available brain oxygen levels and electrical activity in 53 of the patients, with most showing flat EEGs. But about 40% of people will have normal or near-normal brain waves again at some point later, consistent with the presence of consciousness. This condition may occur even 60 minutes after CPR is performed on a patient with cardiac arrest.

Of the 567 patients, only 53 survived. The researchers interviewed 28 of these survivors and an additional 126 people from the community who had experienced cardiac arrest (because the sample size of survivors in the new study was too small). Nearly 40% reported that they had some perception of the dying process but no specific memory. 20% of people seem to have "recollections of death experiences." Parnia said many people who had "recollections of death experiences" described the event as a "moral assessment" of "their entire life and conduct."

Researchers found that only one survivor interviewed could recall the name of the fruit in a recording played while he was receiving CPR. But Parnia also acknowledged that the man might have gotten it right by accident.

Parnia and colleagues proposed a possible hypothesis to explain their findings. Typically, there is a "brake system" somewhere in the brain that filters out most elements of brain function so that they do not enter conscious experience - this allows people to function efficiently in real life. Because under normal circumstances, "you don't have access to the full range of the brain's activity in the realm of consciousness," Parnia said.

The researchers' hypothesis is that in the brains of people who are dying, the "braking system" is removed. Parts that are normally dormant become active, bringing the entire brain activity of a dying person into the realm of consciousness—"all your thoughts, all your memories, everything that was in your head before," Parnia said. We don't know what evolutionary role this served, but it seems to prepare people for the transition from life to death."

The findings also raise questions about the brain's ability to recover from hypoxia. "It's possible that some people who were traditionally thought to be unsavable could actually be saved," Parnia said. "Doctors' conventional wisdom is that once the brain is deprived of oxygen for five to 10 minutes, it will die. Our study can It proves that the brain's ability to withstand prolonged hypoxia is quite strong. This opens up new avenues for finding solutions to treat brain injuries in the future."

The new study "is a major effort to understand as objectively as possible the nature of brain function as it may apply to consciousness during cardiac arrest and near-death experiences," said Lakhmir Chawla, who is an intensive care unit physician at the Jennifer Moreno Veterans Affairs Medical Center in San Diego, California, who, while not involved in the study, has published papers on spikes in EEG activity when patients die.

While the results reported by Parnia and colleagues are "startling" from a scientific perspective, Chawla believes: "We should also think about the human nature of these data. First, the findings should motivate clinicians to Treat patients receiving CPR as seriously as we treat conscious patients, but in practice we rarely do this. Second, for those patients who appear to be irreversible, doctors can ask family members to come and say goodbye, as the patient may still be I can hear my family’s voices.”