Patient Resources
Get Healthy!
Science Reveals Possible 'Surge of Consciousness' Just Before Dying
- May 2, 2023
- Dennis Thompson HealthDay Reporter
Near-death experiences -- seeing a bright light, floating outside your body, watching your life flash past, communicating with lost loved ones -- could well be part of a dying brain's final fight-or-flight response, a new report suggests.
Electroencephalogram (EEG) readings of dying intensive care unit patients found that some experienced a surge of brain activity in regions associated with consciousness and perception of vision and sound.
The patients in which this brain surge occurred also showed signs of a fight-or-flight response in their dying moments, with heart racing and lungs gasping for breath, said senior researcher Jimo Borjigin, an associate professor of neurology and molecular & integrative physiology with the University of Michigan Medical School.
This struggle "might trigger the alert system of the brain, which then leads somehow to realer-than-real consciousness processing,"Borjigin said. "They're not breathing. They're not moving. But internally, their brain is on fire."
These human studies follow years of animal studies in which researchers monitored the brains of lab rats as they died from cardiac arrest, Borjigin noted.
"A human brain is far more complex than an animal's,"Borjigin said. "We wanted to see whether there's any possibility that we could get brain activity that somehow correlates with neural signatures of consciousness."
The researchers took EEG readings from four patients who passed away due to cardiac arrest. All four were comatose and unresponsive and, with their families' permission, were removed from life support.
Upon removal of ventilator support, two of the four patients showed an increase in heart rate along with a surge in gamma wave activity, which are considered the fastest brain waves and are associated with consciousness.
Further, the gamma wave surge occurred in the so-called "hot zone"of consciousness, the junction that connects the temporal, parietal and occipital lobes in the back of the brain.
Prior brain studies have associated these temporo-parieto-occipital (TPO) junctions with dreaming, visual hallucinations during epileptic seizures, and altered states of consciousness, the researchers noted.
Stimulation of the temporo-parietal junction can produce out-of-body experiences, Borjigin said, while other parts of the junctions are important for auditory perception and visual consciousness.
But this brain surge only happened in the two patients who responded to ventilator withdrawal with physical signs of a fight-or-flight struggle prompted by the sympathetic nervous system.
"What's surprising is the two patients who had this response had an appropriate sympathetic nervous response to ventilator withdrawal, whereas the other two patients didn't have increased heart rate when the ventilator was removed,"Borjigin said.
The two dying patients who experienced this gamma wave surge also had prior experience with seizures, Borjigin said. They weren't seizing in the hour before they died, but their earlier experience might have primed their brain to undergo this response at the end of their lives.
"I believe that we now have a pretty good handle for potentially explaining why you see a very bright light, why something is realer than real, why it is possible that somebody could be having an out-of-body experience, why somebody could see or think they saw their relatives but it's coming from their own memory,"Borjigin said. "They are able to dig into their memory stores and recall life events."
The findings were published May 1 in the Proceedings of the National Academy of Sciences.
This study jibes with exploration of "covert consciousness,"a field of research examining brain activity in people who appear to be in a vegetative or minimally conscious state, said Dr. Joao Gomes, section head of the Neurointensive Care Section at the Cleveland Clinic's Neurological Institute in Ohio.
"They have actually found out that there is some level of consciousness in these patients that previously were thought to be unconscious,"trapped in a coma, Gomes said. The subject is a bit controversial, but the scientific understanding of consciousness is evolving as the technology used to gauge brain activity improves, Gomes noted.
At the same time, records of dying brain activity date back centuries, Gomes noted.
"Back in the reign of terror in France, when they were guillotining a lot of people and there were a lot of decapitations, there was this physician who would take the heads and examine them,"Gomes said. "And he actually reported that many of them had brain reflexes that were intact. He claimed some of these people actually would follow commands, minutes after decapitation."
Still, many questions remain about the phenomenon, including why the brain would have this response in its dying moments.
"Why would a brain build a mechanism like that? Is there any survival advantage?"Borjigin said. "Clearly, we know autonomic system activation is for survival. But beyond that, to have the visual activation, the auditory activation, to have an out-of-body experience, what is the physiological significance of that? Why would the brain want to activate that kind of system? That's something we don't know."
There's also one serious drawback to the new research -- the patients who experienced the surge in brain activity didn't survive to describe what they experienced, Borjigin said.
She hopes that EEG readings can one day be taken of people suffering cardiac arrest who survive their ordeal, so researchers can ask them what they saw or felt. Those personal experiences could then be compared back to the person's brain activity.
Borjigin said this research is driven by more than morbid curiosity, and could help save people who are near death.
"People have this idea that if you're looking at the last moment of somebody's life, what's the medical relevance of that? Why is that important to study?"Borjigin said. "We've been arguing if you don't know how exactly individuals die, how can you save them? It really does have relevance to cardiac arrest, and potentially the role of the brain in cardiac arrest."
More information
The Cleveland Clinic has more about the fight-or-flight response.
SOURCES: Jimo Borjigin, PhD, associate professor, neurology and molecular & integrative physiology, University of Michigan Medical School, Ann Arbor; Joao Gomes, MD, section head, neurointensive care section, Cleveland Clinic's Neurological Institute, Ohio; Proceedings of the National Academy of Sciences, May 1, 2023
