By Jon Holmlund
The latest mind-blowing (seriously, no pun intended) report from the science literature is that a team of scientists at Yale Medical School have been able to use an artificial preservative solution to recover electrical activity in some of the cells of the brains from the severed heads of pigs that had been slaughtered for food. This is absolutely stunning because the understanding—so widely accepted that the term “conventional wisdom” is trite in this case—that the brain’s need for oxygen, nutrients, and the blood flow that provides them is so massive, so constant that an interruption of even a few minutes means irreversible death of brain tissue. This can be in part of the brain (as in a stroke), or the whole brain (as in brain death). Your correspondent is not a neuroscientist, but understands that recent research is showing the human brain, anyway, to be more adaptable than historically understood, meaning that after an event like a stroke, function can be restored over time with rehabilitative efforts that support the remaining, undamaged brain tissue adapting to the damage.
In this case, it was four hours after the pigs’ deaths that the researchers isolated their brains and put them into the solutions. Besides the electrical activity in some nerve cells, the researchers also found evidence that blood vessels could support circulation, and that there was metabolic (energy-using) activity in the isolated brains. Evidence that the whole brain was working, and able to, for example, “feel” pain or detect stimuli, was not evident, but the researchers were not trying to do that. Their immediate goal was apparently to understand how long brain cell function might be preserved.
Before we rush to invoke the immortal Viktor Frankenstein, it should be said that the researchers in this case appear to have carefully followed existing ethical guidelines for the research use of animals. And it is tempting to speculate about this work leading to new treatments for brain injury.
Still, many ethical issues are raised. What constraints should proper ethics of experimentation on animals put on future, similar experiments? Is it acceptable to pursue a model for whole animal or even human brains preserved outside the body to study preservation and restoration of function, perhaps even to the point of trying to “jump start” the whole brain, as the current researchers speculate might be necessary. Or, such a recovery might be impossible; they say they might just be observing an evitable process of brain death and decay. Maybe it takes rather longer than previously appreciated.
That last point raises further concerns about how we understand when death has occurred. Do current approaches toward harvesting human organs for transplantation, that may require that blood flow to the brain be interrupted for only a matter of minutes before declaring death of the donor, effectively jump the gun? Might some people who are thought brain dead in fact have better chance of recovery than appreciated? These questions already trouble ethicists thinking about how to determine when a person has died.
These are only a few of the concerns, and some authors this week are calling for an international review of the ethics of this work, before proceeding further with research on mammals—never mind humans, that’s not in view, yet.
A summary of the work for the non-specialist is openly available. Summaries of related ethical issues, also openly available, can be found here and here. The full scientific report in Nature requires subscription or purchase.