In 2013, a team led by Jimo Borjigin at the University of Michigan slid electrodes into the cortices of laboratory rats, induced cardiac arrest, and watched what happened in the brain during the thirty seconds it took to die. The dying rats did something nobody expected. Their electroencephalograms lit up with a burst of high-frequency gamma oscillations that were highly synchronized and coherent—exceeding levels seen during normal waking states. The brain, in the moments after the heart stopped, was not switching off. It was firing in patterns that looked, by every standard neural measure of consciousness, hyperaware.
The paper landed in a major scientific journal and immediately became one of the most cited and most argued-over results in the small, contested field of dying-brain neuroscience. Borjigin’s lab had not set out to study near-death experiences. They had been recording neurochemistry in rats and noticed, by accident, that the EEG signal after cardiac arrest looked strange. They went back, designed the experiment properly, and confirmed it: in those final seconds, the rat brain produced a transient flood of gamma-band activity, with cross-regional coupling that exceeded the waking baseline.
What gamma waves are, and why coherence matters
Gamma waves are the fastest electrical rhythms the cortex produces, and neuroscientists have spent two decades linking them to conscious awareness, attention, memory binding, and the moment a perception clicks into place. When you suddenly recognize a face in a crowd, gamma synchrony spikes across the visual and frontal areas of your brain. When you fall into dreamless sleep or general anesthesia, gamma collapses. MIT neuroscientist Earl Miller has proposed that the flexible organization of cortical gamma activity is essentially what cognition and consciousness are made of.
Coherence is the part that makes the Michigan finding so disorienting. A loud signal in one brain region is not, on its own, evidence of anything rich happening. What matters is whether distant regions are oscillating together. In the dying rats, frontal-to-posterior gamma coherence rose to levels substantially higher than waking values. Cross-frequency coupling, where slow rhythms organize fast ones, also surged. The standard quantitative markers neuroscientists use to flag conscious processing all pointed in the same direction at once.
The leap from rats to near-death experiences
A substantial minority of people who survive cardiac arrest report a near-death experience: a feeling of leaving the body, a tunnel, an encounter with deceased relatives, a life review compressed into seconds, an overwhelming sense of meaning. The phenomenology is consistent enough across cultures that researchers have built standardized scales to score it. The puzzle has always been mechanistic. How can a brain that is, by clinical measure, shutting down generate experiences that survivors describe as more vivid and more real than ordinary waking life?
Borjigin’s proposal was straightforward. If a rat brain can mount a coordinated gamma surge in the seconds after cardiac arrest, a human brain might do the same, and that surge could be the neural substrate of the imagery survivors report. Other researchers have since extended the argument, suggesting that the gamma burst could underlie the hallucinations, autobiographical replay, and altered sense of self that characterize the experience. A dying brain stripped of oxygen would release a cascade of neurotransmitters, lose inhibitory control, and briefly enter a state of disinhibited cross-talk between areas that normally police each other.
A human case in 2022
The rat work would have stayed a curiosity if not for an accident in a hospital. An elderly man with epilepsy was being monitored on continuous EEG when he had a heart attack and died. The recording captured roughly 15 minutes around his death, including 30 seconds before and 30 seconds after his heart stopped. Researchers analyzed the trace and found, in the seconds bracketing cardiac arrest, a surge of gamma-band activity with increased cross-frequency coupling. It was a single case, recorded under uncontrolled conditions, and the man’s brain was already abnormal from years of seizures. The pattern matched the rats.
That paper, published in 2022, did what the rat study could not. It put a human EEG next to the rodent data and showed the same general signature. It also drew enormous criticism. One brain. Epileptic. No controls. The authors themselves were careful not to claim the man experienced anything specific. They simply noted that the oscillatory patterns observed are the kind associated, in healthy brains, with memory retrieval and dreaming.
The 2023 follow-up that pushed the case further
In a subsequent study, Borjigin’s team examined four comatose patients at the University of Michigan who had been removed from life support with family consent. Two of the four showed a surge of gamma activity in the dying brain, concentrated in a region called the posterior cortical hot zone, an area implicated in conscious experience by other neuroscientists. The other two patients showed no such surge. Whether the difference reflected pre-existing brain injury, medication, or something about the dying process itself, the team could not say. But two of four human brains, monitored at the moment of death, did the thing the rats did.
The pattern has since been folded into broader debates about consciousness at the edge of life. Researchers continue to argue over whether near-death reports reflect a genuine conscious state mounted by a failing brain, or a reconstruction assembled later from fragments of returning awareness. The gamma data do not settle the question. They constrain it.
What survivors actually report
The phenomenology is the part most outside the laboratory. Studies of cardiac arrest survivors have found that a meaningful percentage recall some form of near-death experience. The experiences often include heightened clarity, time dilation, geometric or autobiographical visions, and an emotional charge that often reshapes the rest of their lives. A multidisciplinary model has proposed that these experiences arise from the brain’s response to lethal physiological stress, with the gamma surge as one candidate mechanism among several.
Skeptics point out that the rat gamma burst lasted about 30 seconds, while some human NDE reports describe experiences that subjectively span hours. Defenders of the gamma hypothesis note that time perception itself depends on cortical rhythms, and a brain in a hyper-coherent gamma state may not be running on ordinary clock time. The rat data cannot tell you what it feels like to be a rat dying. It can tell you that something neurally extraordinary is happening in those seconds.
The harder question
None of this resolves the deeper argument about what consciousness is. If a brain in the first seconds after cardiac arrest produces gamma coherence higher than the waking baseline, two readings are possible. Either the dying brain is briefly generating a more vivid experience than ordinary life, which would fit survivor reports of hyperreal clarity, or gamma coherence is not the marker of consciousness neuroscientists have taken it to be, and something else is doing the work. Some theorists have begun proposing that consciousness has structural features that ordinary EEG cannot fully capture, and that the dying brain is a useful natural experiment for testing them.
The Michigan rats are long gone. Their EEG traces, archived as digital files, still show the burst: a sharp climb in high-frequency power, frontal and parietal electrodes locking into phase, the signal flaring for 20 to 30 seconds, then collapsing into the flat line that defines clinical death. Whatever the rats experienced, if they experienced anything, lasted about as long as it takes to read this paragraph.
Cardiac arrest kills roughly 350,000 Americans outside of hospitals every year. A small fraction are resuscitated. A smaller fraction of those report something. The gamma surge, if it generalizes, is happening in brains all over the world, every minute, unseen because nobody is recording. The Michigan study’s strangest implication is not that near-death experiences are real or unreal. It is that the last thing a brain does, before it stops, may be the most coordinated thing it ever does.
