Paranoid Schizophrenia.

The brain is malfunctioning, it perhaps contains a brilliant intelligence or valuable information, but the dopamine receptors respond abnormally.

The artificial brain to which it is uploaded is designed to correct such unbalanced perception and thinking and so the mind is enabled to re-write it's own thinking on a new and more reality-based perceptual basis, thus developing a paradigm of cognition more conducive to socialisation and "good-will" to all.

Ever tried to get toothpaste back into the tube? Brains usually swell when removed from a warm body.

Even if they didn't, you can't just shove a fresh brain into an empty skull - every cranium is a different shape, even among identical twins.

A machine brain, though, can be small enough that it is one size fits all (as long as the recipient body doesn't have microcephaly). You can fill in the empty spaces with some paste.

Infection/Cancer

The organic brain is healthy for now but has been infected with some problem that will destabilize it in the near future. Deep-seated tumors are easy solution: brain cancer can leave a patient functional for decades and then kill instantly as the tumor crosses a particular size boundary where it cuts off a key section of the brain.

Any viral infection could have the same effect. An infection opens the story possibility that the infection was deliberately done by some malevolent actor (seeding brain cancer is harder). The downside is it is less obvious how an infection is leaving the brain healthy enough to function currently — there are viruses that would do that, but you’ll spend more time explaining the medical to average reader, whereas cancer is pretty well within typical zeitgeist (at least for US audiences).

I've read your question a couple of times and as I see it, you have not stated that the brain has to be removed to be "Read".

As such, it could be "Read" while still in the dying body. Given the delicate nature of the cerebral cortex, the brain could die of shock once it is severed. This could also apply to a cloned brain: it doesn't survive its removal from it's growth environment to be able to be placed in a new body.

As such, only artificial brains will work.

The body, being more robust and "re-startable", could be resuscitated once the new brain is attached.

Uploading to a synthetic brain isn't a necessity. It is just common sense.
The synthetic brain is superior to the original wetware in so many ways, that a person would have to be crazy to not upgrade.

• Synthetics have greater memory capacity


• They run faster.


• They run longer... potentially forever.


• They aren't reliant on blood flow to sustain cognitive functionality.


• They come with on/off switches on all pain-reporting nerves.


• Inter-cranial cellular voice and data communications are available


• Upload-able knowledge sets (in case you ever want to fly a helicopter)


• Daily backups


• Total VR (like regular Virtual Reality, but delivered with individual nerve cell granularity; indistinguishable from real life.

With all these advantages and more, everybody goes synthetic, so finding a doctor who knows how to do a wet-to-wet transfer is going to be pretty tough. Besides, synthetic brain transfer is covered by conventional insurance. Doing something weird like transferring into a cloned biological brain... that is going to be a very expensive, cash-in-hand proposition.

It is this last, economic aspect which is the real barrier. The insurance companies don't want to have to pay for a new wet-to-wet biological brain transfer every few decades when each organic brain wears out. It is much cheaper for them in the long run to pay for synthetic one time and then just plug that immortal brain-box into cheap replacement bodies every time any of the non-cognitive systems break down.

What if you change the method of transferral? Right now you assume that the brain is somehow capable of transmitting its entire state to a machine, but while we can transmit thoughts we can't really transmit the exact configuration of our brains and their connections that make our personalities.

So instead (if your story allows) you can make it a deep and detailed scan of the brain that determines every nerve connection and the position of every chemical in the brain. This is processed by a computer into intelligent data that the artificial brain can use to simulate your personality, knowledge and intelligence. Unfortunately the deep scan is invasive and will damage and kill the brain it scans.

Alternatively when you connect the brain to a computer the connections will eventually deteriorate the brain or the interface itself. If the brain deteriorates you die, if the interface deteriorates you can suddenly lose control of parts of the body if you don't have tons of expensive and invasive maintenance every few months, which you kind of have to avoid.

You know how you can plug a monitor into pretty much any computer and it'll work?

Human brains and their bodies do not work that way. While the function of moving one's arm is, in fact, localized to one area of the brain, the specific neural connections that allow one to control one's arm are just that -- specific to that person. Same goes for every minute biological function that the body performs.

Thus, a brain transplanted straight into another pile of meat would work, but it would promptly die -- the "breath regularly" function in the brain would get rewired to the "wiggle your toes" nerves in the body. Attempting to blink would release the subject's bowels. Etc. All in a completely random fashion.

There are two options to ameliorate the situation. 1) Put the subject into a coma for months or years while the brain re-learns how to work its new body (the body, meanwhile, will require near comprehensive life support). Or 2) put the subject into a computer, map out the neural "interface" of the individual (i.e., figure out that brain's version of "breath", "blink", "wiggle toes", etc, and reconfigure the body to match the brain (or vice versa).

Depending on the computing capacity of your timeline, this may or may not work. For context, though, there are 100 trillion neural connections in the brain. Even today, copying that much data is relatively mundane (difficult, and not something an individual would do on his PC, but definitely doable at scale. If each neural connection is a byte, that's 100 terabytes of data). So the "copy brain to computer" bit will be relatively easy. Evaluating each connection and ascertaining its function? Frankly, it can take as long as you want it to take.

Alternative: "What, do you think we have empty humans just lying around? Even if we could stockpile them, it takes energy to keep them alive! Way too expensive. Gotta grow 'em fresh!"

It takes time to grow a clone.

If someone has serious long-term health problems, growing a clone and transplanting the brain is a reasonably safe process.

If someone is badly injured, but gets to the hospital alive, the doctors can put the brain in a generic body, then give the person anti-rejection drugs for a few weeks until their clone is ready.

If there was an accident where X people were seriously injured, but there are only X-1 generic bodies available, that's a problem. The patient is already dying, the nearest ready body isn't even in the same city, and then a doctor remembers that his friend was working on an brain scanner.

It is an interface issue. Your technology has one step that converts the brain to computer data

Reading out the personality and memories of a person from their brain requires that the brain is intact, for otherwise parts of the personality or memories would have been lost and the artificial copy would be incomplete.

It has a second step that connects that computer data to to a prepared body.

The artificial brain is then placed into a real human body.

You don't say if the "real body" is a clone or a donor body (ethical consideration ignored)

As your artificial brain is an improvement on the original human brain. Your artificial brain is able to identify and orginize the correct connection for each communicating nerve. This task would be impossible for the human surgeon connecting an organic brain.

In short, because the artificial brain is connected in mass to the spinal nerves, and it figures out on it's own what goes where.

Why not stick with the reason why we don't transplant brains now? There are too many blood vessels to cut and reattach. In order to transplant a brain, we'd have to cut each blood vessel going to the brain, attach it to a temporary blood vessel, keep it supplied with oxygenated blood, and repeat for each blood vessel until all the originals are detached. Then we would have to transfer to the new body, removing the temporary attachments and making permanent ones.

Transplanting a brain would be a tremendously difficult operation.

By contrast, attaching an artificial brain would be much easier so long as it doesn't rely on blood for delivering fuel. Then you just have to connect the neurons, not the blood vessels. And you don't need to worry that the brain will die during the transfer, as it is powered separately (e.g. by battery).

Keeping the brain alive in the old body is much easier than transplanting it. That just requires keeping the blood supply flowing and oxygenated. Perhaps ensuring sufficient nutrition. Presuming your brain download can be done in a day or two, that doesn't seem like an intractable problem.

This still sort of handwaves at the problem of doing the download or building the artificial brain, but I see those as outside the scope of the question. The reason why they don't do a brain transplant is that they can't. It's too difficult. This is science-based in that that is one of the problems that they face now. So it just isn't fixed in your story.

Backups.

The procedure backs up the full information taken from the brain in separate storage, which enables the building of a second artificial brain.

Mental clones are forbidden by law (or are they? plot potential here...), but the second brain can be built to replace the first one in case of another terrible accident.

Every night while the patient sleeps, their brain transmits differential information via intenet to the backup facility, so they'll just lose the last day of memories if they get destroyed. Functional immortality.

(This is actually a common hope of future technology in the real world's transhumanist community.)

With such a feature, a biological brain transplant becomes obviously inferior. The scanning technology necessarily destroys the biological brain.

This creates a spinoff plot hole: why is not everyone else doing it, even when perfectly healthy? To close it, make the procedure sufficiently expensive and very risky, say 90% risk for a 20-year old and getting higher for older brains, becoming borderline completely impossible for the very old.

neurodegenerative diseases can gradually destroy a brain, especially if it was a genetic condition. Transplanting the brain won't help, and the brain is still intact in the sense that such a condition is yet to set in. So if there is a chance for a brain transplant, your be far better off with the artificial brain rather than having to scan the brain and transplant to an artificial brain anyway once the condition have set in.

Alternatively, if your patient is of some especially rare serotype for certain antigens present in his/her brain, and his/her body condition does not permit time for a cloned body, then there may not be specially prepared bodies of the serotype available, which means that an organic brain transplant will always meet lethal rejection reactions. Maybe immunosuppressive drugs doesn't work for this specific rare serotype antigen present in this brain. Then an artificial brain maybe the only option.

I once wrote a paper on the feasibility of a brain transplants. There was a website at the time offering to do it for half a million (body included). The major problem I have with brain transplants in sci-fi is that you want to transplant the entire central nervous system which includes the spinal cord and eyes/ears. Peripheral nerves regenerate while central nerves do not. You would start by cooling the brain down to reduce the need for oxygen. Then cut all the peripheral nerves and blood vessels. Then pull the CNS out of the outer meninges and move the CNS to the new body. Finally reconnect nerves and blood vessels.

I also think there's a right way to transfer an organic brain to an artificial brain which is slow and neuron by neuron.

I think if you combine these two ideas you're left with many diseases that would fit your story. Huntington's disease for example is what Thirteen had in the House TV show.
But also common things like blindness, spinal cord injury, cancer, and multiple types of degenerative brain diseases.

You want scientists in your story to be ethical and helpful? You need blanket ban on brain transplants. Period.

You said:

I don't want there to be an immoral decision (e.g. reading out the personality destroys the brain and the 'evil' scientists chose to kill a person to test their experimental technology).

Answer me then, have you considered other side of brain transplant? What happens to replaced brain? Since you make it unambiguous that brain hosts entirety of personality (which might not be entirely true, between Spinal Cord and Autonomous Nervous System, there has to be feedback causing reactions, wants or desires which we would classify as part of personality), then we can simplify issue I'm approaching to following question:

What happens to replaced personality?

Your world needs to redefine murder. Murder isn't killing of a body, it's possible for body to survive without brain activity for years even today (insert joke about your designated dumb-and-hated demographic), murder is killing of a mind. Death is death of personality. It would be interesting to refer to those who suffered trauma necessitating emergency brain digitisation, because body can't sustain brain under any conditions any more, as post-mortal.

So, where or how do you get body to transplant into without going all-in on capital E Evil?

Evicting someone from body is as evil as it goes. Toss in debts, body repossession and you have a canvas for very ugly cyberpunk dystopia. Something similar was done in Freejack.

Paying someone to give up body is no better. It's same ugly cyberpunk dystopia with immortal upper class. Fantasy would do that with vampires or other undead literally feeding off of peasants (metaphor for all upper classes ever feeding off of lower classes proverbial lifeblood is lurking somewhere here).

Growing brain-dead clones? Assuming you can grow clone fast and in dedicated cloning vat, how do you ensure there was no brain development since zygotal phase? Otherwise you end up killing severely mentally challenged human. Perhaps severely enough to be nonfunctional, but killing still.

Only using bodies that had brains removed in unfortunate, but genuine accidents? There are two issues.

First, how do you guarantee genuineness of accidents? Between Panama Papers, recent Epstein revelations and occasional reports about organ black market showing how much rich and powerful can get away with even today, how do you know there are no covert hit squads faking accidents people for hyperlites? Homeless in good health and other people not missed by many would be cheap and easy to disappear, perfect for lower upper class, but truly rich could afford to stage and cover up accident of, say, less known football players to enjoy young, strong body.

Second, if you have some phlebotinum that can prevent first issue, what about families of deceased one? Donating organs of someone dead is quite a bit different than your friend or family member suddenly becoming complete stranger in most literal of senses. I have a hard time imagining this becoming acceptable, but I admit, my imagination might simply be failing me.

Therefore it is my opinion that if you want to have non dystopian world, you need a blanket, consistently enforced, ban on brain transplants.