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Problem: One time I went to a Target in Indiana and all the “Non-Fiction Bestsellers” were arguments for the existence of heaven, with the exception of Cheryl Strayed’s Wild and maybe a cookbook or something. A lot of the evidence for these popular and controversial books comes from the testimonies of people who’ve had near-death experiences and, upon recovery, claim they’ve seen heaven, based on incredibly lucid visions they had as they approached death. And they’ve gotten some support from scientists—neurosurgeon Eben Alexander in his October 2012 Newsweek cover and corresponding book outlined his own heavenly encounter during a near-death experience.

If you fear death, as you should, it’s easy to see why these theories are popular. But a study published on Monday in the Proceedings of the National Academy of Sciences offers a more scientific explanation for this phenomenon.

Methodology: Researchers from the University of Michigan created a near-death experience for nine anesthetized rats by inducing cardiac arrest with an injection of potassium chloride. They recorded the rats’ electroencephalogram (EEG) signals to measure their brain activity in the frontal, parietal and occipital cortices. A separate experiment did the same thing with rats that had inhaled CO2.

Results: The researchers found that after cardiac arrest, the rats experienced a surge of high-frequency brain activity. “Cardiac arrest induces a level of cortical directed connectivity in the near-death brain that far exceeds that observed during the waking state,” the study reads. The rats were having a near-death experience.

The researchers were able to connect this veritable brain explosion with death specifically and not just cardiac arrest, because the EEG readings were nearly identical as the rats approached death from CO2 inhalation.

Implications: These results provide “strong evidence for the potential of heightened cognitive processing in the near-death state,” the researchers write. These brain fireworks could account for some of the things people experience after staring death in the face only to return to tell the tale—visions and voices, a feeling of blissfulness, etc.

But the experiences feel real, because as Oliver Sacks put it in his rebuttal in The Atlantic to Alexander’s theory, “the fundamental reason that hallucinations—whatever their cause or modality—seem so real is that they deploy the very same systems in the brain that actual perceptions do.” And you can’t blame people for wanting to believe.

The study, "Surge of neurophysiological coherence and connectivity in the dying brain," was published in the current edition of the Proceedings of the National Academy of Sciences.

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