Dr Nenad Sestan has a technique to recover some functioning neurons from dead brains. He’s been collecting decapitated pig heads from slaughterhouses and hooking them up to perfusion pumps and running an oxygenated saline (plus other secret ingredients) through them, and then doing physiological assays on the brain tissue, finding that significant numbers of the neurons are still viable and show signs of cellular activity.
There was no evidence that the disembodied pig brains regained consciousness. However, in what Sestan termed a “mind-boggling” and “unexpected” result, billions of individual cells in the brains were found to be healthy and capable of normal activity.
This work has not yet been published in a peer-reviewed journal, so take that “billions” number with a grain of salt. Even if accurate, and I don’t think there’s any way he could have accurately gotten a good count, it still means that only a small percentage of the cells in the brain retained any capacity to function. It is mostly dead, and ignoring the Princess Bride reference, mostly dead is completely dead. The integrated whole is non-functional. The pig is not thinking, not dreaming, not awaiting the kiss from its true love to awaken. It is unresponsive. It is an ex-pig.
Sestan now says the organs produce a flat brain wave equivalent to a comatose state, although the tissue itself “looks surprisingly great” and, once it’s dissected, the cells produce normal-seeming patterns.
The lack of wider electrical activity could be irreversible if it is due to damage and cell death. The pigs’ brains were attached to the BrainEx device roughly four hours after the animals were decapitated.
Put that four hours in context. If your brain is deprived of oxygen for four minutes, irreversible damage begins. After about six minutes, you are dead and typically beyond resuscitation. Within that window between the onset of damage and death, the functional network of the brain begins to break down, and victims have an increasing chance of being reduced to a comatose vegetable.
Those pig brains were deprived of all oxygen and nutrients for 240 minutes. “Comatose” is a generous assessment of their state. You’ve no longer got a brain, you’ve got a scattering of individual cells that no longer work together, but haven’t quite gotten the message that they’re supposed to decay, or haven’t yet been chewed up by bacteria or the wash of lytic enzymes released by their definitely dead neighbors.
This is not a surprising result. No one expects that there is an instant of death in which every cell ruptures their membranes and disintegrates into a liquid acellular mass. It takes time for a mass of meat to break down completely. It is a slight surprise that they can salvage useful single cells after hours of breakdown, but only slightly.
Is this a useful observation? Yes. It would be nice to have another source of neurons for laboratory work that doesn’t require maintaining a colony of animals that you have to personally kill to extract the very freshest cells. You can also use this surviving subset to trace functional activity, which is apparently the goal of the research. It’s going to have new problems, though: how do you interpret the cellular activity of a neuron that has been hypoxic for four hours? Is it actually comparable to newly isolated or cultured cells? The Sestan lab has a lot of work ahead of them. It’s also likely to be extendable to animals other than pigs: human brains donated to research might provide a pool of living cells for physiological work.
But realistically, this is more like discovering that you can go down to the local junkyard and find an unbroken passenger side front window for a 1998 Toyota Corolla that you can use to replace the one someone broke on your car, or a replacement starter motor for your Jeep Cherokee. It does not mean that we can expect a zombie car uprising as the whole junkyard starts up and rushes to clog up the nearest freeway.
Unfortunately, it is also priming unrealistic and irrelevant ethical dilemmas.
The one type of research he thinks may call for quick action to set up rules of the road is Sestan’s unpublished brain preservation technique (which the Nature editorial did not discuss). “If people want to keep human brains alive post mortem, that is a more pressing and realistic problem,” says Hyman. “Given that it is possible with a pig brain, there should be guidelines for human tissue.”
It is not a pressing or realistic problem. What is described as a concern is not possible with a pig brain — I have to say it again, those are dead, non-functional, unsalvageable brains, although a tiny fraction of the cells might have some utility for research. Still, it could become a legitimate ethical issue, so I can see where the responsible ethicist will set up guidelines before it becomes a problem.
Imagine a situation where a patient is dying of organ failure, but their brain is still healthy. If we could decapitate them, hook them up within seconds to the pumps and fluids that Sestan pioneers, keeping their brain intact and undamaged and healthy in a nice little vat, should we? Given that there is no known technique for reconnecting such a brain, it might be greater torment than allowing them to die — would you want to spend decades in a sensory deprivation tank, just for the sake of living? That’ll be a fun one for the bioethicists to wrestle with.
But this technique is not currently anywhere close to raising this problem.
What I see as a greater problem is this annoying essentialism. It’s HUMAN, it’s a HUMAN brain, therefore we need to regard it with the same requirement of respect we accord to HUMAN BEINGS. There is a difference between an adjective and a noun. It is human tissue, yes, but it has none of the properties essential to a good definition of a sapient human being (which we don’t have in most people’s heads: they’ll talk about 46 chromosomes, or parentage, or attributes of the human body like having one head and two arms and two legs, which are all pretty much irrelevant to personhood, I would think), so people freak out over human organoids, little blobs of brain tissue around a millimeter across in a dish, or over chimeras, small subpopulations of human cells in an animal host.
As far as I’m concerned, the Sestan experiment has been grossly overhyped, although it has real potential, and the ethical gasps are actually in response to an imaginary situation, rather than anything that has happened yet.
Lest anyone think I said anything the ethicists don’t already know, I should include this bit from one of them:
Hyman…thinks most of the scenarios are exaggerated or unlikely. It’s hardly possible a tiny brain organoid will feel or think anything, he says.