Pigs for Brains

In contention to the idea that brain death is lethal, researchers have successfully revived the disembodied brains of pigs – four hours after their initial termination. Although it was not clear how wide spread the revival was within the brains’ numerous regions, or whether consciousness is also capable to being reinstated, the study does raise contemplative questions surrounding the ethics of the approach as well as the nature of death itself; the existing medical and legal descriptions of death inform routines for resuscitation and organ transplantation.

These pig-brain revival experiments were published in the journal Nature on 17 April. It detailed how researchers at Yale University in New Haven coupled the brains to a system that relayed a blood substitute to and throw. The procedure restored some baseline functions, like the ability of brain cells to produce energy, maintain their own structure and remove toxins.

In a majority of countries, a person is classified as dead when brain activity shuts down, or when the heart and lungs cease to function. The brain is high maintenance and complex, requiring an inordinate amount of nutrients, oxygen and energy production, and going without these key ingredients for little more than a few minutes is thought to cause irreconcilable damage.

Previous studies have demonstrated researchers’ ability to take brains cells many hours after death and revive their baseline metabolic functions. As well, scientists, early on in the twentieth century, had conducted experiments that kept animals’ brains alive the instant the heart stopped, through cooling the brain and circulating a blood substitute within it; yet, it was not clear how successful this was. These precursor studies led Yale neuroscientist Nenad Sestan to think it possible to revive a brain hours after death.

Sestan put his hypothesis to the scientific test: after acquiring 32 severed pigs’ heads from a nearby slaughterhouse, his team went about removing each brain from it’s encapsulating skull and placing each organ in a chamber, where a catheter would be inserted. Exactly four hours after death, the team began funnelling a warm preservative solution into the brain’s veins and arteries.

The system, BrainEx, closely mirrors blood flow by brining nutrients and oxygen to brain cells and the surrounding white matter. The solution the researchers used also contained inhibitory chemicals that prevented complex electrical brain activity from restarting –effectively put the brakes on any chance of consciousness being reignited.

Sestan and his team examined how well these brains functioned during a six-hour period. They discovered that the brain cells began to regain normal and essential metabolic functioning, with the brain’s additional immune functions also coming back to life. Sestan termed this revived functioning of billions of cells as “mind-boggling” and “unexpected.”

Sestan’s team, who used BrainEx to keep pig brains functioning for up to 36 hours, do not think their pursuit for brain revival will take them toward the consideration of restoring electrical activity. Instead, their aim is to investigate how long this system can maintain a brain’s metabolic, immune and other physiological functions without a body present. “It is conceivable we are just preventing the inevitable, and the brain won’t be able to recover,” Sestan opines. “We just flew a few hundred metres, but can we really fly?”

The BrainEx system can only maintain its functional competencies to a brain outside it’s skull, meaning this contraption is a massive leap away from becoming useable on people. Sestan, however, did acknowledge that surgeons sought his opinion on if this brain preserving tech could have medical utility. Disembodied human brains, he mused, could be used to test potential cancer and Alzheimer’s treatments considered simply too risky to try on the living.

This maintenance system, jestingly termed the “brain in a bucket,” would conjure up serious legal and ethical questions if it were ever to go near a living human.

For instance, if a person’s brain were to be reawakened “in a bucket,” with complete sensory deprivation, would it suffer indefinitely and be subject to complete hysteria, without anyway to communicate? Would the brain be able to simulate the sense of self and identity that a person feels and would the brain be able to retrieve memories? Would it be considered correct to use such a brain as a disposable treatment guinea pig?

“There isn’t really an oversight mechanism in place for worrying about the possible ethical consequences of creating consciousness in something that isn’t a living animal,” says Stephen Latham, a bioethicist at Yale who worked alongside Sestan’s team.

Calculating the degree in which a brain is aware, without its usual integration with a body, would be problematic. “We could imagine that the brain could be capable of consciousness,” said George Mashour — a neuroscientist at the University of Michigan in Ann Arbor who studies near-death experiences — to the scientific journal Nature. “But it’s very interesting to think about what kind of consciousness, in the absence of organs and peripheral stimulation.” Sensory deprivation, it has been shown, can lead to people hallucinating a sensory reality, but it is unknown how much suffering a constant fluttering in and out of hallucination would cause an isolated brain to experience.

Sestan’s study also presents questions regarding the nature of brain damage and death. Many physicians have assumed for years that even minutes without oxygen can induce irreversible damage to the brain. Yet, the pig brain study could suggest that the brain could remain workable for a couple of steps longer than previously thought, even without the other assets a body provides. “This paper throws a hand grenade into the middle of what the common beliefs are,” says Becker, an emergency-medicine specialist at the Feinstein Institute for Medical Research in Manhasset, New York,. “We may have vastly underestimated the ability of the brain to recover.”

The world of organ donation, in addition, could also be in for an ethical debate. For instance, in some European countries, first medical responders who cannot resuscitate after a heart attack will sometimes attempt to use a system that distributes oxygenated blood throughout the body, without the inclusion of the brain, to maintain organs for potential transplantation. But, if a BrainEx styled technology does become ethically and practically feasible, the ability to extend the period of resurrection could have a knock-on effect for the pool of eligible organ donors.

“There’s a potential conflict here between the interests of potential donors — who might not even be donors — and people who are waiting for organs,” says Stuart Youngner, a bioethicist as Case Western Reserve University in Cleveland, Ohio.

Sestan’s study has opened a pandoras box of questions regarding the nature of death, and whether it is ethical to revive consciousness without knowing what the subject’s experience could entail. “This really is a no-man’s land,” Christof Koch — president and chief scientist of the Allen Institute for Brain Science in Seattle, Washington – told Nature “The law will probably have to evolve to keep up.”

 

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