These brain scans of dying patients may reveal what happens when you die

A mysterious burst of brain activity after two patients died provides clues as to what happens in our last moments

By Troy Farah

Science & Health Editor

Published May 3, 2023 5:30AM (EDT)

Computer artwork of an ECG (electrocardiogram) trace in front of a human brain (Getty Images/PASIEKA)
Computer artwork of an ECG (electrocardiogram) trace in front of a human brain (Getty Images/PASIEKA)

What happens when you die only you will ever know — because once it happens, there is usually no coming back and telling anyone about it. For the very rare occasions in which someone technically dies and is resuscitated, their stories can be otherworldly: those who've seen the so-called "other side" report golden tunnels of light, encounters with angelic beings, echoing voices and even the appearance of deceased relatives. These reports intrigue scientists because they are common across multiple cultures, regardless of religious background; but given their nature, they aren't easy to study. To do so, you would have to record someone's brain waves right as they were about to die, and be ready for that moment. 

Which is exactly what researchers did in a new study. 

The whole experience of meeting Jesus or your dead grandparents could be explained by this strange brain activity.

Published in the journal Proceedings of the National Academy of Science, the study describes the brain activity of four patients as they died in the neurointensive care unit at the University of Michigan. The researchers used an EEG, or electroencephalogram, a device that records the electrical activity of the brain using small, metal discs called electrodes that are affixed to the scalp. It translates the communication between neurons into squiggly lines, which can tell us something about what's happening inside someone's skull — although it's also quite limited technology and not even close to mind reading.

Each of the patients was comatose with essentially no chance of recovery. Life support was removed with the approval of the patients' family members. Three were women between the ages of 24 and 77 and one was an 86-year-old man.

So what actually happened upon death? Well, when ventilators were removed from two of the patients, their heart rates shot up accompanied by a surge in gamma waves, which are forms of high-frequency electrical activity in the brain.

Gamma waves are associated with waking consciousness, especially working memory processes and attention. Distortions in these neural ripples are associated with disorders like Alzheimer's disease, as well as hallucinations and epileptic seizures. People with schizophrenia, for example, experience "spontaneous" bursts of gamma activity.

What's more, the location of these waves in the dying patients' brains are also intriguing. In both patients, these gamma waves were localized to areas of the brain — specifically regions where the temporal, parietal, and occipital (TPO) lobes meet — associated with processing auditory, sensory and visual information. But these brain waves were also "global" meaning they spread out to other parts of the brain, connecting different parts of the brain, including the prefrontal cortex.

All of these regions are considered important because they enable numerous cognitive functions associated with perception. In a sense, all of reality — or what we think it is — can be condensed to how these lobes interact.

"Because this posterior cortical zone activated in dreaming largely overlaps with that identified in waking, the TPO junctions are considered a 'hot zone' for the neural correlates of consciousness," the authors write.

Of course, neuroscience is incredibly complicated and it's not always easy to reduce what is happening in one part of the brain to actual consciousness. In other words, just because one part of the brain is lighting up doesn't necessarily mean that a specific process is actually occurring. Our brains aren't as neatly compartmentalized as popularly believed and any cognitive phenomena are incredibly complicated. We know far, far less about these relationships in a brain that is dying.

"How vivid experience can emerge from a dysfunctional brain during the process of dying is a neuroscientific paradox."

Nonetheless, the fact that gamma waves were triggered during death in these regions is quite remarkable. However, what all this means isn't exactly easy to tease out. It could indicate that near-death experiences are a result of this kind of brain chatter. The whole experience of meeting Jesus or your dead grandparents could be explained by this strange brain activity. After all, the brain does produce its own psychedelic drugs, though typically in trivial amounts — maybe a squirt of DMT is what people who have near death experiences receive.

Or these gamma waves could just be random signals or bursts of electrical energy that don't mean much. The dying patients may not have been actually aware, or experiencing anything. They were already dead or dying. Either way, it's a jump to say. It's worth noting that both patients had a history of seizures, though there were no such episodes within the 24 hours leading up to their death and their bodies did not move in an epileptic-like fashion.

"How vivid experience can emerge from a dysfunctional brain during the process of dying is a neuroscientific paradox," Dr. Jimo Borjigin, an associate neurology professor and the study's lead author said in a statement. "We are unable to make correlations of the observed neural signatures of consciousness with a corresponding experience in the same patients in this study. However, the observed findings are definitely exciting and provide a new framework for our understanding of covert consciousness in the dying humans."

Their research correlates with previous research published a decade ago by Borjigin in which rats were surgically implanted with electrodes, injected with anesthesia and a mixture of potassium chloride, which caused the animals' hearts to stop. Similar to the dying humans, the rats experienced a "transient and global surge of synchronized gamma oscillations," which are the same signals observed in the two patients.

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While this is a pretty small sample size of just two individuals — and notably, the other two patients didn't experience such a surge in gamma waves — it isn't easy finding someone who is about to die while also being able to scan their brain. A previous study published last year in the journal Frontiers in Aging Neuroscience was the first to ever describe the brain waves of a dying patient in any detail. It was also completely accidental. The researchers were studying the patient's brain waves for an unrelated reason when he, an 87-year-old man, died unexpectedly from a heart attack.

The researchers were able to record what happened because the patient had a "do not resuscitate" order, meaning doctors weren't allowed to try to revive him. They reported similar gamma wave activity, but also changes in other signals in the brain. The more recent study sheds more detail on what happens as people die, but it's still quite a jump to say anything specific about what these individuals may or may not have been experiencing.

"Since it was observed in patients during the dying process," Borjigin and her colleagues write, "we cannot rule out the possibility that the surge of gamma power is a sign of a pathological process unique to the dying stage and unrelated to conscious processing. Mechanism and function of the observed gamma power surge during the dying process warrant further investigation."

Because of their rarity and association with death, it's not easy to study this kind of thing, but as the researchers note, this may be the closest we ever get to answering this question. Unlike euthanizing rats, it's very unlikely a similar study would ever be approved in humans. Of course, much more research is warranted, difficult as it may be and this study lays the groundwork for future research into the strange obscurity of consciousness and death.

By Troy Farah

Troy Farah is Salon's science and health editor specializing in drug policy and pandemics.

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Brain Consciousness Death Dreams Dying Gamma Waves Near-death Experience Neuroscience Schizophrenia Science