The brains of decapitated pigs have been kept alive for as long as 36 hours, raising the possibility of human brains existing outside the body.
A team at Yale University have experimented on up to 200 pigs' heads, taken from an abattoir roughly four hours after the animals' slaughter, by connecting them to a system called "BrainEx".
Neuroscientist Nenad Sestan, who led the team, described their four year-long work to the US National Institutes of Health on 28 March, as reported by MIT Technology Review.
Using the system of pumps, heaters and bags of artificial blood, Prof Sestan described how billions of individual cells were found to be healthy and capable of normal activity after circulation was restored to the pigs' brains.
He branded this a "mind-boggling" result, although he saidthere was no evidence of the pigs' brains regaining consciousness.
Prof Sestan suggested use of the system, dubbed "brain in a bucket", would probably not be unique to pigs and was likely to work in any species, including primates.
Surgeons at Yale have reportedlyalready enquired about medical uses, including suggestions that disembodied human brains could be used to advance treatments for cancer and Alzheimer's that are too dangerous to trial on living people.
The study is likely to provoke ethical questions, such as whether the work could be developed further to preserve human brains outside a body – an area explored in sci-fi and horror movies.
Prof Sestan said: "People are fascinated. We have to be careful how fascinated."
Currently, those hoping to prolong their life after death have resorted to having their bodies cryogenically frozen, in the hope medical science will be able to bring them back to life and cure their conditions at some point in the future.
The Yale team found, despite the health of the tissue, the pigs' brains were in the equivalent of a comatose state.
Commenting on the "unchartered territory" of further advancements, Prof Sestan said: "That animal brain is not aware of anything, I am very confident of that.
"Hypothetically, somebody takes this technology, makes it better, and restores someone's [brain] activity.
"That is restoring a human being. If that person has memory, I would be freaking out completely."
Prof Sestan told the MIT Technology Review he did not want to elaborate on the work, which has been submitted for publication in a journal, saying he had not intended for his remarks to become public.
This week, he joined 16 other academics in publishing a joint editorial in the journal Nature regarding the ethics of experimenting with human brain tissue.
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They wrote: "Experimental models of the human brain could help us to unlock mysteries about psychiatric and neurological illnesses that have long remained elusive.
"But to ensure the success and social acceptance of this research long term, an ethical framework must be forged now, while brain surrogates remain in the early stages of development."
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