Most people contemplate the moment of death. Whether there is white light or not, it is one of the moments that people are most scared of.
A recent study suggests that a final "recall of life" may indeed take place in the near-death state. Published in the journal Frontiers in Aging Neuroscience, its authors write, "We report what is to our knowledge the first continuous EEG recording from the human brain in the transition phase to death."
And the brainwaves they recorded followed patterns similar to those of higher cognitive processes such as memory recall or dreaming.
The study was serendipitous. Doctors in Vancouver, Canada were treating an 87-year-old man for head injuries after a fall, when he developed epilepsy. They used continuous electroencephalography to detect his seizures, during which he suffered a fatal heart attack.
"We measured 900 seconds of brain activity around the time of death and set a specific focus to investigate what happened in the 30 seconds before and after the heart stopped beating," said Dr. Ajmar Zemmar in a press release by the University of Louisville, in the U.S. state of Kentucky, where he's a neurosurgeon. Zemmar, who organized the study, was a resident at Vancouver General Hospital at the time.
"Just before and after the heart stopped working, we saw changes in a specific band of neural oscillations, so-called gamma oscillations, but also in others such as delta, theta, alpha and beta oscillations."
Brain oscillations, or brainwaves, are patterns of rhythmic electrical impulses. Different wavelengths are associated with different cognitive functions, and the patterns described in the study are similar to those during meditation or memory retrieval. This suggests "the brain may be playing the last recall of important life events just before we die, similar to the ones reported in near-death experiences," Zemmar speculated.
Neurologist Dr. Frank Erbguth, president of the German Brain Foundation, isn't surprised by the results of the study. "(Finding that) the human brain creates its imagery in certain situations is nothing new," he said, noting that it's known to occur in migraine patients as well as drug users. "So near-death experiences are similar to a wide variety of phenomena in which the brain produces pictures."
The experiences are readily explicable, according to Erbguth. When we die, the concentration of carbon dioxide in our brain cells rises, he said. "This alters brain electricity and brain metabolism – these are the two keyboards where near-death experiences are located."
People who are very good at meditating can evoke similar experiences, he added. Their EEGs show increased brainwaves in the gamma spectrum, similar to those observed in the study. "And we know that these gamma activities indicate memory retrieval," he said.
Gamma waves are fast, with a frequency range starting at about 30 Hz. "The gamma band can't be seen in a conventional EEG," said Erbguth, remarking that its inclusion in the study's brainwave analysis, therefore, offers new insights.
An American study conducted on rats in 2013 found a similar increase in gamma-band activity in the first 30 seconds after cardiac arrest. The authors of the recent study write that the overall similarity in brainwave changes in the two studies suggests that "the brain may pass through a series of stereotyped activity patterns during death" in multiple biological species.
They concede, however, that several caveats must be considered before venturing any generalizations, chief among them that their findings involved a single patient who was heavily medicated after suffering a traumatic brain injury resulting in hemorrhaging, swelling and epileptic seizures.
"Epileptic activities of this kind mean that brain electricity is thoroughly shaken up," making it difficult to conclude a normal dying brain, points out Erbguth.
All in all, he says, the recent study provides another facet to the already comprehensive body of knowledge about the dying brain. When blood circulation stops, the brain shuts down communication between nerve cells, certain brain electricity rhythms shift, and cells have an electrical output one last time.
In 2018 in the journal Annals of Neurology, the American and German neurologists published results of their research on the human brain's reaction to oxygen deprivation following cardiac (and hence circulatory) arrest. They described the release of a massive wave of electrochemical energy known as "spreading depolarization."
Studies of this kind receive a lot of attention, Erbguth says, because they're thought to perhaps give a glimpse of what's behind death's curtain. "But all that we're looking at takes place in front of the curtain," he counters since even people who have reported near-death experiences were only close to exitus and not dead.
Be that as it may, Zemmar said his and his colleagues' study may give some solace to surviving family members: "Right now, we don't know anything about what happens to their loved one’s brain when they're dying. I think if we know ... that they're remembering nice moments, we can tell these families and it builds a feeling of warmth."
Erbguth is less sanguine. "Our brain is at least still able to produce images," he remarked – as evidenced by descriptions of near-death experiences and also reasonable to assume of a dying brain. But resuscitation medicine studies show that while two-thirds of patients who report such experiences say they were pleasant, the other third say the scenes were terrible, he pointed out.
"I'd be happy if passage into death is accompanied by nice memories," he said, "but I'm afraid it's not within our control."
