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In the world i'm developing it's already possible to periodically scan your brain so you can keep a backup in case of you dying (people have rejuvenating treatments but they can still die of unnatural causes) so you can implant it into a lifelike cybernetic body (expensive) or an organic body grown in an artificial womb, that gets implanted with a 3D-printed organic brain copyed from yours (way more expensive).

But if you don't have the money to buy a physical simulacrum for your consciousness, you can simulate it inside a virtual body in a virtual world.

Now the question is: computational power aside, how much information would it be necessary to simulate a brain virtually, would you need to scan the synapses of a working, living brain, or would just the neural structure be enough, so you could reconstruct someone's conscience from a dead brain?

I thought about using some sort of advanced computerized tomography to scan the brain but i'm not quite sure if it would be enough depending on the information necessary.

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  • $\begingroup$ You will need both the neurons and all the connections between those neurons, aka synapses, a map of the neurons without their connections (that idea seems more than a little like an oxymorons to me to be honest, but whatever 🤗) is going to just be meaningless garbage for the purpose you envision. $\endgroup$
    – Pelinore
    Commented Jul 1, 2022 at 18:12
  • $\begingroup$ Reconstructing someone's conscience from a dead brain is like reconstructing an unsaved Word document from a turned-off computer. When the computer is turned off, or the brain dies, the running state is lost. Irretrievably lost. Gone forever. $\endgroup$
    – AlexP
    Commented Jul 1, 2022 at 18:14
  • $\begingroup$ I think the chances are more than good that the only thing you risk losing is 'perhaps' some very short term memory @AlexP .. practically everything else is liable to be in the 'hard drive' memory, coded in the connections between neurons. $\endgroup$
    – Pelinore
    Commented Jul 1, 2022 at 18:18
  • $\begingroup$ @Pelinore: I had no idea that somebody got a Nobel prize for showing that long-term memory is encoded in the connections between neurons. Linky? (As far as I knew, decades out of date probably, long-term memory is encoded in the state of the neurons and the state of the connections. That is, knowing that there is a connection doesn't help; you need to know the state of the connected neurons.) $\endgroup$
    – AlexP
    Commented Jul 1, 2022 at 18:21
  • $\begingroup$ @AlexP I wasn't aware that the common consensus that neural connections where what allowed us to form and recall memories had been plausibly challenged. Linky? 😁 You may be right mind, I've never focused much on precisely this aspect and it's been a while since I read anything related to it 🙂 $\endgroup$
    – Pelinore
    Commented Jul 1, 2022 at 18:27

1 Answer 1

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We Don't Know

Consciousness is not something we've puzzled out yet. The brain operates both via synaptic connections and neurochemical interactions, there may even be quantum effects, it's incredibly plastic (damage to one section might do, as far as the owner and observers can tell, nothing, while a different section might destroy their personality, and that isn't the same between any two people).

Rather than just tomography, you would probably need an advanced fMRI, and probably sensors placed surgically inside the brain - this all assuming that you can capture all the necessary information nondestructively. It is much, much more likely that what you could arrive at is something that convincingly simulates the consciousness you're attempting to copy, but which cannot be demonstrated to be the same person.

(On the other hand, that is both an interesting ethical question and potentially a subject that would keep people from wanting to use your brain scan, which is an interesting worldbuilding concept.)

As for just "how much data would I need"? We have an early example, in a Google brain mapping experiment: here.

The brain map, which is freely available online, includes 50,000 cells, all rendered in three dimensions. They are joined together by hundreds of millions of spidery tendrils, forming 130 million connections called synapses. The data set measures 1.4 petabytes, roughly 700 times the storage capacity of an average modern computer.

Assuming that knowledge of the cell locations and synaptic connections is enough (and you don't need the quantum/chemical data), you could scale this up. There are approximately eighty-six billion neurons in the brain, so you'd just need 2.58 zettabytes of storage. There are currently estimated to be about 40 zettabytes of digital data on all media in the entire world, so you could store about 30 brains - again, assuming no other data is needed to accurately simulate the behaviour of the brain. Also, this assumes that the scaling-up is linear (it's probably not exponential as synapses only stretch so far, but it's probably not strictly linear).

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    $\begingroup$ @Pelinore: We need all the connection and the states of all the neurons and all the connections. $\endgroup$
    – AlexP
    Commented Jul 1, 2022 at 18:15
  • $\begingroup$ @AlexP Yep, wouldn't disagree, was what I said after all 🙂 .. or do you mean states as in gate open gate closed? not so sure I'd agree there, synapses and neurons aren't pc chip architecture. $\endgroup$
    – Pelinore
    Commented Jul 1, 2022 at 18:20
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    $\begingroup$ Looking into Physics World's Impact Factor and the practices of IOP publishing, I am inclined to agree w/r to the linked article, @Pelinore. But when no less a luminary than Roger Penrose posits a quantum effect to consciousness - well, to quote the linked article, "Their theory is almost certainly wrong, but since Penrose is so brilliant, we’d be foolish to dismiss their theory out of hand." $\endgroup$
    – jdunlop
    Commented Jul 1, 2022 at 18:25
  • $\begingroup$ And @Pelinore - I imagine AlexP is referring to excitation states. As you say, neurons and synapses are not PC chip architecture, so there are gradations... which is another nuance that is likely to be difficult to capture and will require yet more storage space. $\endgroup$
    – jdunlop
    Commented Jul 1, 2022 at 18:26
  • $\begingroup$ @Pelinore - I have removed the linked article, and weakened the suggestion of quantum effects, but I cannot dismiss Penrose. $\endgroup$
    – jdunlop
    Commented Jul 1, 2022 at 18:27

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