Andriy Onufriyenko via Getty Images
We’ve all heard eerie stories about people who almost perished, but survived to tell the tale of the strange visions and emotions they experienced when they were close to death. Now, scientists have observed a surge of energetic activity in the brains of dying patients, a discovery that reveals that our brains can be active even as our hearts stop beating, reports a new study.
The results challenge a longstanding assumption that brains become nonfunctional as they lose oxygen during cardiac arrest, and could eventually open a new window into the weird phenomena associated with near-death experiences (NDE).
Jimo Borjigin, an associate professor of neurology at the University of Michigan, has been interested in these questions since she first observed surges of activity in the brains of dying rats a decade ago. The surges consisted of gamma waves, the fastest oscillations in the brain, which are associated with conscious perceptions, lucid dreams, and hallucinations.
Now, Borjigin and her colleagues have discovered similar gamma activity in the brains of patients who died in the hospital while they were monitored by electroencephalogram (EEG) sensors, which record neural activity. The researchers examined EEG readings from a small sample size of four unresponsive patients who were removed from life support with the permission of their families. During cardiac arrest, two of the people experienced complex gamma activity in a “hot zone” of the brain that is critical for conscious processing.
The new observations “demonstrate that the surge of gamma power and connectivity observed in animal models of cardiac arrest can be observed in select patients during the process of dying,” according to a study published on Monday in Proceedings of the National Academy of Sciences. The findings could also help explain near-death experiences, which the study described as “a biological paradox that challenges our fundamental understanding of the dying brain, which is widely believed to be nonfunctioning” during death.
“The dying brain was thought to be inactive; our study showed otherwise,” said Borjigin, the senior author of the study, in an email to Motherboard. “The discovery of the marked and organized gamma activities in the dying brain suggests that NDE is the product of the dying brain, which is activated at death.”
“As far as I am concerned, our study may be as good as it will ever get for finding neural signatures of near-death consciousness,” she added. The “only thing better than this is to have the patients survive to tell the tale that correlates with the detected neural signatures.”
It’s impossible to know what the patients felt as a result of the enhanced activity in their brains, though Borjigin said the data hints at a subjective experience that might involve visual or auditory dimensions. In this way, the study may have provided an empirical counterpart to reports of near-death experiences, which often include strikingly similar phenomena, such as the presence of light, or a sense of levitation, or a highlight reel of memories.
The study is part of a recent wave of research that complicates our typical idea of death. A recent study monitored the vital signs of over 600 people as they died, and found evidence of cardiac activity minutes after a patient flatlined. The researchers said the observed activity would not support brain function, however.
More research will be needed to establish a link between death and gamma activity in the brain, in part because the study is based on a small sample size, making it difficult to draw broader conclusions. It’s also not yet clear why only two of the four patients experienced gamma activity during death. Both of those people had a history of seizures, which could account for the findings, though neither patient had experienced a seizure in the hour leading up to their deaths.
Given her work on animal models, Borjigin was not surprised that the dying human brain can also undergo a surge of activity. However, the patterns and intensity of the brain waves contained some unexpected details that will need to be examined in future research. For instance, the brains of dying rats were active in all EEG channels, while the human brains were active at specific frequencies.
“The gamma activation in the dying patients was detected in only two patients; this needs to be confirmed in more patients,” Borjigin said. “The activation patterns differed even among the two patients; does this mean the two patients had somewhat different subjective experiences internally at their final moments? What exact EEG features correlate with ‘seeing light’ or ‘seeing relatives,’ ‘out-of-body sensation’ or ‘life review? How are these potential sensory percepts encoded back to the brain for later recall if they survived? These are all unsolved questions in need of further studies and in need of funding support to do so.”
To solve these riddles, Borjigin and her colleagues plan to collect more observations of dying brains, which might help to expose the underlying meaning of these gamma surges. This line of research could shed light on the deeply mysterious phenomena of near-death experiences, which have sparked widespread fascination among experts and the public alike.
“What excites me most is to probe the role of the brain in cardiac arrest from these studies,” Borjigin said. “Our data reveals that the dying brain is far from hypoactive. Then, why would a dying brain be activated? What is the function of brain activation at near-death?”
“Producing an internal state of consciousness (NDE) cannot be its sole function when survival is truly at stake,” she concluded. “Much of my future research will focus on the role of the brain in cardiac arrest, including covert consciousness.”