Although scientists are unsure, an increase in a specific type of high-frequency wave in dying brains may be related to final conscious experiences.
Some people’s brains produce a spike of impressively organized-looking electrical activity in the final moments of their lives, which may or may not reflect consciousness. Scientists are unsure of this phenomenon.
The current study, which was released on Monday (May 1) in the journal PNAS(opens in new tab), shows that this surge can occasionally happen before the brain shuts down but after a person’s breathing stops. Due to the activity pattern’s resemblance to that seen while people are awake or in dreamy states, it has been hypothesized that these electrical surges may represent the extrasensory experiences recorded by persons who have experienced near-death experiences: a tunnel and white light, the ability to view the body from the outside, or the ability to revisit significant moments in time.
However, it is impossible to know if the patients in the new study had such experiences because they all passed away in the end.
“If you talk about the dying process, there is very little we know,” said Jimo Borjigin, a neuroscientist at the University of Michigan Medical School and the study’s principal investigator. According to Borjigin of Live Science, it is uncommon for patients to have their brains continuously monitored as they pass away. This study may be the first to demonstrate the death of the brain second by second.
Near-death encounters
Some people who have been saved from imminent death have described hearing or seeing unexplained things while receiving CPR or when they appear to be unconscious. It’s unclear why these near-death experiences occur and whether they are really unique to death.
According to international surveys, only approximately half of what people refer to as “near-death experiences” truly take place in potentially fatal circumstances, according to Daniel Kondziella(opens in new tab), a University of Copenhagen neurologist who was not involved in the new study. According to Kondiziella, the other half take place during meditation or in frightful circumstances that don’t jeopardize one’s health or interfere with brain metabolism.
The problem is that you cannot tell from the experience whether someone has had a cardiac arrest, syncope (a momentary loss of consciousness), or a close call with a car collision, according to Kondiziella.
It’s difficult to tell whether those who genuinely die also have these subjective experiences because those who survive to describe a near-death experience are essentially different from those who die — their brains don’t permanently lose function, for example.
Borjigin and her coworkers monitored electrical activity in the brains of rats they had put to death by cardiac arrest in 2013(opens in new tab). They discovered that the brain had an increase in gamma waves, the brain’s highest-frequency electrical oscillations, for roughly 30 seconds after the heart stopped. Gamma waves are one of many signs that a person might be alert and aware; they are connected with conscious experience but do not necessarily indicate that a person is conscious.
An electroencephalogram (EEG), which measures electrical activity on the surface of the brain, was being used by a different team of medical professionals to monitor the brain of an 87-year-old man in 2022 when the patient passed away suddenly. The man’s brain displayed an increase in gamma activity in the 30 seconds before and after his heart stopped, much like Borjigin’s rats did.
‘Reading’ the dying brain
Borjigin and her team purposefully used EEG to record the brain’s appearance during death in their most recent study.
The study team received approval to keep an eye on patients in intensive care who were dying and whose breathing assistance had been turned off after treatment proved ineffective. Four individuals in all, all of whom had experienced cardiac arrest, were included in the study.
Two of the four patients’ brains displayed surges in gamma waves in the 30–2 minute period following the removal of their ventilators. The gamma waves in one area of the brain were connected to predictable activity patterns in other parts of the brain, which is an intriguing indication of structured gamma activity.
Gamma waves were particularly active in the temporoparietal junction, a portion of the brain located behind the ear where the temporal and parietal lobes converge. According to Borjigin, this area is known to become active during dreams or out-of-body experiences.
According to Raul Vicente(opens in new tab), a neuroscientist and data scientist at the University of Tartu who co-authored the 2022 article but was not engaged in Borjigin’s work, the new findings confirm what was observed in the 87-year-old patient who passed away unexpectedly. He told Live Science, “It’s quite good to get a confirmation.
“The more consistent findings we have, the more evidence it is that this likely is a mechanism happening at the time of death, and if we can pinpoint this down to one location, even better,” said Ajmal Zemmar, co-author of the 2022 study and a neurosurgeon at the University of Louisville Health.
Zemmar and Vicente are hopeful that these signals may represent evidence of conscious experience just before passing away. But Kondziella is more dubious, which is in line with the discussion in the industry.
“We know that when you die a cardiac death as opposed to a brain death, that takes time,” he stated. He said that between the heart stopping and the death of brain cells, minutes elapsed. It shouldn’t come as a major surprise that abnormal electrical activity would occur in the brain during those minutes.
In these situations, some people might have what Kondziella called “near-death experiences,” but we may never know for sure. A more likely explanation for near-death experiences that include both life-threatening and non-life-threatening experiences, he said, may be “REM sleep intrusion into wakefulness,” a condition in which the brain combines waking and dreaming states. And once more, these experiences may not be unique to death. Dreaming and brain activity patterns, such as gamma waves and other lower-frequency waves, that are strikingly similar to those of waking hours are signs of REM sleep.
In an effort to strengthen the case that the dying brain may produce predictable gamma-wave patterns, Borjigin’s team is still gathering data on end-of-life patients. Similar mind-reading may be possible with unconscious and dying patients, according to Vicente. Other research teams have already tried to use artificial intelligence to identify objects that people saw in their dreams(opens in new tab) based on their brain activity.
If we collect enough data, “this opens an opportunity at some point to be able to decode what people in different coma states are thinking,” Vicente said.
This article is for informational purposes only and is not meant to offer medical advice.