Scientists from Yale University say they've successfully kept dismembered pig brains alive without their bodies for as long as 36 hours - an experiment that could redefine death as we know it.

The "mind-boggling" announcement has been met with both excitement and ethical concerns - if the same thing could be done with human brains, the technology could potentially open up strange new possibilities for life extension. 

Yale neuroscientist Nenad Sestan described the work on March 28 at a meeting at the National Institutes of Health, which aimed to investigate the ethical issues surrounding the latest research in neuroscience.

According to Sestan, his team has experimented on between 100 and 200 pigs obtained from a slaughterhouse. 

Using a system of artificial blood, heaters, and pumps, the team say they were able to restore circulation to the brains of pigs that had been decapitated around four hours earlier. The technique, known as BrainEx, kept the reanimated organs "alive" for as long as 36 hours. 

To be clear, there's no evidence that these brains were conscious. EEG scans showed the brains put out a flat brain wave, similar to an unresponsive, comatose brain.

But in what Sestan said was an "unexpected" result, the team found billions of individual brain cells were healthy and capable of normal activity.

In a simplistic sense, at least, that would technically make the organ alive.

"These brains may be damaged, but if the cells are alive, it's a living organ," Steve Hyman, director of psychiatric research at the Broad Institute in Cambridge, MA, who was at the meeting, told Antonio Regalado at MIT Technology Review.

"It's at the extreme of technical know-how, but not that different from preserving a kidney."

The big caveat here is that Sestan and his team haven't had their results published in a peer review journal as yet. But they have submitted the paper, and so Sestan told Regalado that he's unwilling to reveal further details about the experiment until after full publication.

This means until we have independently verified evidence, we need to take everything with a big grain of salt.

But apparently since early last year, a growing group of scientists and bioethicists have been speculating on the Yale project.

In addition to opening up ethical debates over whether human brains treated the same way would be considered "alive", the research would have benefits for the lab community - allow scientists to study intact and healthy brains in unprecedented detail.

Sestan and his team created the technique in the hopes of constructing a comprehensive atlas of connections between human brain cells, as well as offering better models and potentially even dismembered test organs for diseases such as Alzheimer's and brain cancer.

So how does it work? While the specific details are thin on the ground, MIT Technology Review reports that the BrainEx technology involves connecting a brain to a closed loop of tubes that circulate heated artificial blood throughout the brain's vessels - allowing oxygen to flow to cells even deep in the brain.

This is similar to the way scientists preserve other organs such as heart or lungs for transplants. 

But it's slightly more troubling when it comes to brains.

In the presentation to the NIH, Sestan admitted the technique would likely work on any species, including primates. "This is probably not unique to pigs," he said.

Although he did speculate on potential human uses, in this case Sestan is confident no lines of life and death were blurred.

"That animal brain is not aware of anything, I am very confident of that," Sestan told MIT Technology Review.

But Hyman added that this could lead to new life extension options. 

"It may come to the point that instead of people saying 'Freeze my brain,' they say 'Hook me up and find me a body,'" he said.

Perhaps because of this, 17 neuroscientists and bioethicists, including Sestan, have published an editorial in Nature this week, arguing that we need new rules and protections in place for experiments on human brains.

"We do not think that these difficult questions should halt this research," the researchers write in the editorial.

"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."