Scientists have managed to partially revive brain function in dead pigs already on their way to becoming bacon.
The achievement has challenged assumptions brain cells begin to irreversibly deteriorate just seconds or minutes after oxygen and blood stop flowing.
"The intact brain of a large mammal retains a previously underappreciated capacity for restoration of circulation and certain molecular and cellular activities multiple hours after circulatory arrest," said Nenad Sestan of Yale University, who led the study, published on Thursday in Nature.
The scientists managed to revive "many basic cellular functions" four hours after the 32 pigs were decapitated, by hooking them up to a system which pumped synthetic blood back into the disembodied grey matter.
Six hours later, the brain's cells were running almost like normal - but this is real-life, not Stephen King's Pet Sematary or Mary Shelley's Frankenstein, and the animals weren't conscious.
"At no point did we observe the kind of organised electrical activity associated with perception, awareness, or consciousness," said co- author Zvonimir Vrselja. "Clinically defined, this is not a living brain, but it is a cellularly active brain."
Synapses in the brain were working, but if electrical activity suggesting consciousness was observed the experiment would have been shut down immediately.
"Everyone agreed in advance that experiments involving revived global activity couldn't go forward without clear ethical standards and institutional oversight mechanisms," said study co-author Stephen Latham, director of Yale's Interdisciplinary Center for Bioethics.
"My first reaction was holy shit," Stanford ethics professor Hank Geely, who reviewed the paper before its publication, told Vox.
"The idea [that] after four hours with no oxygen, or glucose, or anything else, most of the cells in the pig's brain would start functioning again? That's astounding."
Even without accidentally creating a zombie pig of sorts, it's still a stunning achievement that promises to accelerate research into conditions like Alzheimer's.
"Previously, we have only been able to study cells in the large mammalian brain under static or largely two-dimensional conditions utilising small tissue samples outside of their native environment," said co- author and PhD candidate Stefano G Daniele.
"For the first time, we are able to investigate the large brain in three dimensions, which increases our ability to study complex cellular interactions and connectivity."
The researchers also hope it'll help develop treatments for patients who've undergone serious brain trauma or been denied oxygen at birth.
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It's unclear when scientists will be ready to try a restore function to recently deceased human brains, or whether consciousness can be restored at all.
"We just flew a few hundred metres, but can we really fly?" said Sestan.
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