I answered this question. I'll quote a passage:

This step requires medical technology that would also allow to transplant a human brain, because if a computer can be connected to the nervous system of a human body, then a human brain can be connected to the nervous system of a human body with the same procedure.

(emphasis mine) and later

I need a medical or technical solution to this logical contradiction.

There have been some claims that the question was actually asking something different, that we should assume that brain transplants are possible and can be done in any circumstance where the brain is intact enough to download. At best though, that is indeterminate. We have these passages that clearly indicate that the asker thought that a brain transplant was just as easy as the artificial implant. That the two require the same procedure.

At best, this is confusing. But confusing should not be read narrowly according to a reader's interpretation. I answered the question as per my interpretation. If my interpretation is incorrect, then the asker should fix the question.

When I read the question, I see it as "Because we can implant artificial brains, we must have the ability to transplant brains. But if we can transplant a brain, why didn't we just do that?" Many are taking "we must have the ability to transplant brains" as a premise. But I don't read it that way. I read it as a consequence of the premise that "we can implant artificial brains". But as I explain, it is not a required consequence. It is quite possible that an artificial brain implant be possible but a natural brain transplant not.

My answer pointed out that it is not necessarily true that a brain can be transplanted if an artificial brain can be implanted. It is strictly more difficult to transplant a brain than to implant one (my answer explains why this is so and doesn't need to be repeated here; I ignore the problems with creating an artificial brain and downloading to it). So there is no logical contradiction. Implanting an artificial brain is possible; transplanting via that same procedure is not.

This can be viewed either as a frame challenge to the premise that an implant being possible necessarily means that a transplant is possible or as additional information. Either view is possible, and either way, it answers the scenario in the question.

It shouldn't matter as rightness/wrongness is not a matter for deletion. But there seems to be some confusion about what I'm claiming. I'm not claiming that it is impossible to reattach blood vessels. I'm claiming that it is impossible to keep the brain alive while disconnecting and reattaching blood vessels.

A typical transplant cuts the blood vessels (and all other connections to the body) of the organ or body part. Then the organ or body part is put in a sterile container inside ice or other coolant. Then it is transported some distance with a delay that may be hours. Then it is attached to the new body, including blood vessels and nerves.

That process fundamentally won't work with a brain. A brain subjected to that treatment would be dead and destroyed. A brain that loses blood flow (and oxygen) dies in minutes, not hours.

As I put in my original answer, the process needed would likely have to keep blood flowing almost continually. This would likely require an artificial blood source that could be connected as the brain is removed from the original body and replaced as the brain is implanted in the new body. And it's possible that we might figure out the nerve problems prior to figuring that out.

  • 1
    $\begingroup$ While the question was deleted for being low quality, it is sufficiently borderline that if this is less a "Why was my post deleted?" question than a "Can my post be reinstated?" question, it could be reinstated. While I agreed with the low quality post flag, and still do, it is a borderline case, and I don't claim to be infallible. $\endgroup$
    – Monty Wild Mod
    Aug 15, 2019 at 13:07
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    $\begingroup$ The answer has been undeleted. Thank you for asking about it on meta. $\endgroup$ Aug 16, 2019 at 2:46

2 Answers 2


As the moderator who deleted the answer that is the subject of the OP's post, my reasoning was this: The answer had been flagged for being low quality, and the question treated brain transplants as an a priori fact.

In addition to my position as moderator, I have a university degree majoring in human physiology. The answer pointed out that connecting blood vessels would be more difficult than connecting neurons. However, in a complete brain transfer, there would be only a few blood vessels that would need to be connected, since any sensible doctor would sever the blood supply at the point where the least amount of effort would be involved to reconnect them to the new body's circulatory system, a task modern doctors should be capable of achieving.

However, the main problem in a brain transplant would be mapping and connecting thousands upon thousands of severed axons and ensuring that each brain-side axon connected to an appropriate body-side neuron. We can't do that today even when the brain remains in its original body, so to be able to do that as a matter of routine in a transplant scenario means that medical technology has advanced considerably, and that the problem of reconnecting blood vessels would be laughably trivial in comparison.

As the post did not in my opinion answer the question, nor did it pose a believable frame challenge, I found the flags to be justified, and hence deletion of the answer similarly justified.

  • $\begingroup$ And why do you think that the neuroscientist's description was incorrect? In particular, why do you think that reconnecting blood vessels could be done quickly enough to keep the brain alive (the problem with neurons is matching and healing). $\endgroup$
    – Brythan
    Aug 15, 2019 at 13:04
  • $\begingroup$ By maintaining the brain on an artificial circulation device, it could be kept supplied with oxygen. It could be attached to the brain by small valved connectors that are bioreplaceable. By connecting the new body's circulatory system to the brain via a closed branch of the valve, the connection could be made while the circulatory device was in place as a shunt, and then once the blood vessels had been connected, the valves could be switched and the circulatory device removed. A fairly trivial engineering solution. The valves would subsequently be replaced by the patient's cells. $\endgroup$
    – Monty Wild Mod
    Aug 15, 2019 at 13:21
  • $\begingroup$ @Brythan We might not be able to do that now, but we're close to it, and by the time that we can map and cross-connect severed and mismatched axons, it should be practically a certainty. $\endgroup$
    – Monty Wild Mod
    Aug 15, 2019 at 13:44
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    $\begingroup$ Regardless of whose neuroscientists are right or wrong, deletion isn't for "wrong"; it's for things that don't attempt to answer or are problematic in some way (incomprehensible, rude, spam, etc). If you think an answer is wrong, downvote and/or leave constructive comments that the author can use to improve the answer. $\endgroup$ Aug 16, 2019 at 2:49
  • $\begingroup$ So...you deleted the answer because it was wrong? Yes, I know you say that you think it doesn't answer the question but that entire assessment relies on the answer being wrong and therefore not answering the question. $\endgroup$
    – VLAZ
    Aug 16, 2019 at 8:10
  • $\begingroup$ After reading the answer in context (since it's been reinstated), I also disagree on not being a believable frame change - it cites a real-world source on why we don't do brain transplants. The question asks why can't there be (living) brain transplants, when artificial ones are possible. I believe the real-world reasons apply here. It's entirely conceivable that it is possible to transplant artificial brains but not possible or at least unfeasible to transplant living ones. There is no conflict between premise and answer - OP doesn't want living brains to be transferred. $\endgroup$
    – VLAZ
    Aug 16, 2019 at 8:23
  • $\begingroup$ @VLAZ, The OP does want living brain transfers, but also wants a reason why occasionally it can't/doesn't happen. $\endgroup$
    – Monty Wild Mod
    Aug 16, 2019 at 12:58
  • $\begingroup$ @VLAZ -- As I've mentioned elsewhere, the frame challenge fails largely because it's out of date (yes, at present we can't transplant biological brains; but in the OP's world, they can and do!) With all due respect to the respondent, a frame challenge for a futuristic scenario should not rely on current knowledge or technology. $\endgroup$
    – elemtilas
    Aug 19, 2019 at 1:05
  • $\begingroup$ @elemtilas I don't find it inappropriate. The question was why is X not possible in the future - the current limitation is quite appropriate. If we can't do X right now, then there is nothing to say we never found a way to overcome the limitation for X, even if we can now do Y and it is related. We don't necessarily need to invent a new one. $\endgroup$
    – VLAZ
    Aug 19, 2019 at 6:27
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    $\begingroup$ Being wrong is what DVs are for. So, guess what you get ;) - The take-away here should be that you are incapable of objectively moderating neuroscience questions. It's a conflict of interest. In the future, for conundrums like this you should pass the buck to another moderator. $\endgroup$
    – Mazura
    Aug 22, 2019 at 1:12
  • $\begingroup$ @elemtilas - if it's a social, cultural, or religious question, sure. If it's a technological question that starts with a handwave and it expects us to invent the middle, then that's no bueno. IMO, it's a story based question anyway, and thus deserves nothing but frame challenges. $\endgroup$
    – Mazura
    Aug 22, 2019 at 1:20
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    $\begingroup$ +1 for coming here and explaining your reasoning. I don't mean that any action in a stack should be justified, but it is the polite thing to do when the matter gets called on meta. Were I in your shoes, I would just have downvoted the OP's answer. $\endgroup$ Aug 22, 2019 at 14:16
  • $\begingroup$ @Renan, Since I also undeleted the answer in question, my subsequent action was to do just that. $\endgroup$
    – Monty Wild Mod
    Aug 24, 2019 at 4:45

I'll take your "B.S." and raise you Technological Superiority.

The premise of the world in the query is that: transfers of data content of biological brains to artificial on a relatively regular basis; and also implantations of artificial brains as well as transplantations of biological brains with relative ease.

Your frame challenge doesn't make sense given the scenario.

I concur: transplanting a brain would be a nightmare procedure with our current understanding and technical ability. But not for the reason you're thinking! Blood vessels aren't the problem --- that's routine reanastamosis which we do with any transplant, any coronary vessel bypass, any peripheral vessel bypass, any tissue flap inset procedure.

What's beyond us at present is the reconnexion of the brain stem to the host spinal cord. If you leave the eyes behind, reconnecting the severed optic nerves will also pose a problem. Once we sort out spinal cord & optic nerve regeneration, I suspect an actual brain transplant could at least be on the distant horizon. (As an aside, they may just take the eyes as part of the brain, though there are other relatively easy to overcome issues by doing so.)

But in the OP's world, those technical hurdles have long been overcome! The question isn't asking whether or not brains can be transplanted but rather why in this narrative circumstance the usual procedure is not being done: i.e., why use an artificial brain when the patient's natural brain is intact.

I suspect this is why your answer was deleted.

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    $\begingroup$ I find your claims to be inferior to those of the neuroscientist that I cited. But beyond that, that's a question of right or wrong. Answers should not be deleted for being wrong. The question does not say that biological transplants are possible in general. It specifically says that biological brain transplants must be possible because artificial brain implants are impossible. That is clearly false and deserves to be challenged. $\endgroup$
    – Brythan
    Aug 13, 2019 at 22:28
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    $\begingroup$ Well, apart from quoting a neuroscientist, what is your experience in the operating theatre? Mine is first hand, and what you claim, that it's the blood supply that precludes brain transplant is simply not the case. I'm not saying dealing with the brain's blood supply is a trivial matter! But the techniques are not beyond a vascular surgeon's capabilities. Apart from that, a moderator saw fit to delete your answer (whether right or wrong, and I suspect said Mod wouldn't know), as I said, because you didn't answer the question asked. You're welcome to disagree and downvote my answer, but $\endgroup$
    – elemtilas
    Aug 14, 2019 at 2:59
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    $\begingroup$ that's pretty much your answer in a nutshell. Also, you are failing to read the question itself. The OP states categorically that biological brain transplantation is generally possible. The OP also states that If the brain was intact ... and transplantation to a new body would have been possible, why did the physicians decide to implant an artificial brain instead of transplanting the original? Clearly, the surgeons are more than capable of implanting either a biological brain or a technological brain. Keep in mind: this is not a question of generalities, otherwise I'd $\endgroup$
    – elemtilas
    Aug 14, 2019 at 3:04
  • $\begingroup$ agree with you! This is a question of specific situation, however. Your answer generalises and in so doing fails to address the specific concern. Your answer is also anachronistic from an in-world perspective. Now I agree with you in the specific point that "just because an artificial brain can be implanted" that it must follow that "a natural brain can also be implanted". However, that's not the issue at hand. It's obvious that in this fictional world, both are routine procedures. This is more a case of poor logic & wording on the OP's part, not a problem with the scenario. $\endgroup$
    – elemtilas
    Aug 14, 2019 at 3:06
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    $\begingroup$ As OP says, answers should not be deleted for seeming wrong. The reasons to delete an answer are outlined in the "Flag answer" form. "It's wrong" is not one of them. $\endgroup$ Aug 14, 2019 at 9:03
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    $\begingroup$ I'll add another "that makes the answer wrong" at best. However, this is not ground for deleting an answer on SE. As sad as it is in some cases where answers can by very wrong. At any rate, the SE mechanism for that is voting - downvotes for answer that is not useful, including incorrect. Flagging and deleting is for things that are not an answer at all - e.g., spam or a completely different question. $\endgroup$
    – VLAZ
    Aug 14, 2019 at 10:59
  • $\begingroup$ I agree that things that are not the brain can be transplanted and the blood vessels reattached. The neuroscientist that I cited says that for the brain, it takes too long to reattach blood vessels and cell death occurs in the brain. It doesn't matter how much experience you have with kidney or hand transplants. You can't project from those to the brain. $\endgroup$
    – Brythan
    Aug 14, 2019 at 11:46

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