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A neuroscientist from Yale University is claiming to have developed a technique that preserves the brain tissue of pigs for an extended period following decapitation. The brains are apparently not conscious, but the new technique is raising a number of important ethical issues.


As Antonio Regalado reports in MIT Technology Review, Yale neuroscientist Nenad Sestan described the new system on March 28 during a meeting to discuss the ethics of cutting-edge brain research at the National Institutes of Health. The technique, called BrainEx, restores circulation to decapitated brains using a system of pumps, heaters, and oxygen-rich artificial blood warmed to body temperature. The point is to restore “micro-circulation,” allowing oxygen to replenish small blood vessels in the brain, including those deep inside. Sestan said he experimented “on between 100 and 200 pig brains,” which he acquired from a local slaughterhouse. The organs, sans body, were kept alive (if it can be called that) for up to 36 hours.

The severed heads were hooked up to BrainEx around four hours after “death.” But because certain aspects of brain function were preserved, and because the brains were effectively kept “alive,” it would be more accurate to say the heads were hooked up after decapitation, rather than after death. Indeed, the technique has the potential to upset traditional conceptions of death, and our sense of when it should be declared. It also speaks to the futuristic prospect of so-called “head transplants.”


All this said, the technique was not designed to enable brain transplants or long-term brain preservation. Instead, it could be used to improve our understanding of the brain’s composition and function, and to develop therapies for comatose individuals, cancer patients, and individuals suffering from dementia, among other neurological disorders.

By using an electroencephalogram (EEG), Sestan’s team detected no signs of consciousness in the pigs’ brains. Rather, they saw a flat brain wave, which is indicative of a comatose state. At the same time, however, the tissue and cells within the brain itself looked “surprisingly great,” in Sestan’s words, appearing healthy, and capable of normal function.

As Regalado notes, Sestan didn’t expect his comments made at the NIH meeting about the BrainEx system to go public, but he did say the results of this work have been submitted to a science journal for consideration.

This isn’t the first time that an animal’s brain has been kept alive outside the body. In the early 1990s, scientists used a similar technique to keep the brains of guinea pigs alive “ex vivo.” The difference here is that the Yale scientists succeeded with a large mammalian brain, which means the technique is likely also applicable to human brains—a possibility not lost on the researchers.


“Hypothetically, somebody takes this technology, makes it better, and restores someone’s [brain] activity,” said Sestan during the NIH meeting. “That is restoring a human being. If that person has memory, I would be freaking out completely.”

Such speculations aside, it’s not clear from the experiments how much damage was inflicted onto the brains, either during the four-hour period following decapitation, or by the BrainEx procedure itself. The technologies and medical know-how required to repair this sort of damage are still likely decades away, so it’ll be a while—if ever—before we see this form of life extension applied to human brains, or the prospect of head transplants.


“It would be a major, pretty much impossible step even to get this far with a human brain,” Frances Edwards, a professor of neurodegeneration at University College London, told the Guardian. “Both in the pig and in a human, the whole brain is only available at death, but in the pig, you are taking a healthy animal and able to control exactly when and how it dies and immediately take out the brain. It would need to be cooled within a few minutes and then only rewarmed when oxygenated.” She said this sort of experimentation isn’t possible for humans, arguing that in cases where an individual has been declared brain-dead, “by the time the brain is accessible it would be well and truly compromised.”

Of more proximate concern is the ethics involved in the Yale experiments. Is the pig actually alive in a meaningful sense? What should the criteria be for the declaration of death? Should death be tied to specific bodily or brain functions, or should it be declared once the permanent cessation of consciousness has been guaranteed? As time goes by, technological advancements will continue to make these questions more difficult to answer.


Sestan said his pig brains didn’t exhibit any signs of consciousness, but what if he’s wrong? Or what if in the future, with a more advanced version of BrainEx, these brains do show signs of conscious awareness? It’s a truly nightmarish scenario, bringing to mind (no pun intended) visions of vats in jars, and brains with no connections to the outside world. Scientists will need to tread very carefully as they venture forward in this area.

And indeed, such was the opinion of a Nature editorial published yesterday by a group of neuroscientists and bioethicists, including Sestan. The authors said new rules and protections are now required for experimenting on human brain tissue, including so-called brain organoids, or mini-brains, human-animal chimeras (intermingling of human and non-human genes), and pieces of human brain tissue removed during surgery.


This is all fine and well, but as the new Yale research demonstrates, we also need to be wary of conducting this sort of research on animals, as the potential for abuse is rather alarming.

[MIT Technology Review, The Guardian]