How to Tell If You’re Dead

The line between life and death has never been clear—and modern technology blurs it further.

Jimo Borjigin never intended to study death. Back in the mid-2010s, the consciousness researcher at the University of Michigan Medical School in Ann Arbor was instead interested in circadian rhythms, the internal cycles that regulate our physical, mental, and behavioral states throughout each day. The circadian clock is a bit of a black box, Borjigin says, so to study it she and her team developed an automated system to continuously monitor neurotransmitters that regulate circadian rhythms in rats.

Over the course of her research, the scientists tracked the animals for weeks at a time, and Borjigin began to notice something unusual. A few of the animals died while under observation, and when they did, the researchers’ sensors recorded a massive and unexpected spike in serotonin for up to 30 seconds after their hearts stopped beating. In humans, serotonin dysregulation has been linked to intense hallucinations, but Borjigin didn’t know what to make of such a finding in the context of rats. Or in death. Like any good scientist, she looked to the literature.

“I was sure we must know everything there is about the death process already, but when I went looking for evidence of this serotonin spike, I found nothing,” she says.

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