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Comment by sonofgod | Hacker News Reader

datapoint, to update to 2020: we can now map a third of a fly brain.

https://www.theverge.com/2020/1/22/21076806/google-janelia-f...

This is probably the most convincing evidence that your mind likely can be uploaded in the near future.

Depends on how you define the near future. There's a bunch of reasons to be skeptical that we'll fully digitize a human connectome anytime soon.

First the fruit fry brain is very small. You can image the entire thing at the microscopic level with a single image. The human brain is massive by comparison. Getting a coherent image that traces an axon from the tip of frontal lobe to the back off the occipital lobe is going to be a huge challenge.

Second the fruit-fly brain has 25,000 neurons while the human brain has more than 10,000,000,000. There's 6 orders of magnitude difference there.

Third, it's highly likely that glia (non-neurons) in the brain play a major role in neural computation so we'll have to image those too. Humans have way more glia than most other animals.

Lastly the connectivity of neurons in the human brain is very high. Getting those little connections right is key in all this as we aren't just going for the neurons but the connections between them.

If you can handle 25k neurons today that's roughly 19 binary orders of magnitude to 10 billion or less than 38 years of Moore's law type doubling, calling it 2 years instead of 18 months per double. So not that scary. There are different kinds of doubling and who knows if it will keep on keeping on.

>Second the fruit-fly brain has 25,000 neurons while the human brain has more than 10,000,000,000. There's 6 orders of magnitude difference there.

>Lastly the connectivity of neurons in the human brain is very high.

yep, the human brain is 100B neurons and has 10e4 connections per neuron while the fly brain has 10e3 connections/neuron. So we need to emulate 10e15 connections of the human brain. GPT-3 has 175B of weights.

Right, but GPT-2 had 1.5 billion neurons in 2019 so GPT-3 was a 100x increase. 1e15 may not be that far off, especially since these operations are relatively straightforward to run in parallel.

Yes, but even then, it's not very convincing.

If you turn a computer off, then try to transfer the software it was running, you will get some data. But whatever was in the volatile RAM, won't get transferred. It's very likely the mind has such data.

Is there much evidence for this RAM-type hypothesis? Many animals hibernate but still have their personality and memories intact, similarly we sleep and can undergo long periods of unconsciousness without us or others perceiving a significant change.

Even drastic measures like electrical shocks or chemicals (up to a point) tend to have temporary rather than permanent effects. That evidence seems to imply that most of what we consider as 'us' is the more permanent physical neuron connections rather than the transient chemical/electrical states.

It's /all/ transient chemical states on a sufficiently long timescale. And the 'critical' timescale varies across different physical systems. (Also, you get severe brain damage after a few minutes without oxygen - that seems pretty damn transient to me.)

Right, but we generally understand the mechanism there. Without oxygen, ATP pumps within animal cells cannot functionj. They can no longer maintain the right ion gradients across cell membranes and are destroyed due to osmotic pressure.

It's a challenge for reading the neurons connectivity for sure, but I don't think it is evidence that there is more to 'us' than our physical neuron connectivity graph.

Well, you've still got the graph of neuron connections, but there are also weights on those connections. (In artifical neural networks, the graph is the architecture, and the weights are pretty much everything...) Per the article:

"Ion channel proteins change shape in response to the electric field across the membrane, opening or closing pores; at the synapse shape-changing proteins respond to electrical changes to trigger the bursting open of synaptic vesicles to release the neurotransmitters, which themselves bind to protein receptors to transmit their signal, and complicated sequences of protein shape changes underlie the signalling networks that strengthen and weaken synaptic responses to make memory, remodelling the connections between neurons."

Can the weight of a connection be surmised after oxygen deprivation? Or are the chemical changes that happen under oxygen deprivation irreversible (from an information theoretic viewpoint)?

Interesting analogy given how it's possible to recover data from RAM for a short period after power is removed, and significantly longer if you freeze it. https://www.zdnet.com/article/cryogenically-frozen-ram-bypas...

Not really. The big question mark in my mind is how important the surrounding biochemistry really is to the brain's function. We already know from the study of mental illnesses that altering the biochemistry can significantly affect a person's state of consciousness and mental abilities. What is less clear is what happens if you remove the biochemistry completely. Does the brain even still function? Does a person go insane? Totally unknown.

As much as a photograph of a sandwich is convincing evidence that a sandwich can be uploaded. That is a picture of the connections in a fly's brain, not an uploaded fly's brain, or a simulated fly's brain.

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