[MURG] RFC - necessary neuron info

[Joseph J. Strout]

At 10:17 PM -0700 10/3/03, digfarenough wrote:

>I'd say its beyond questioning that some basic
>information is needed: cell shape and connectivity,
>receptor concentrations in various parts of the cell,
>and other things likely.

Agreed.

>I propose that ionic concentrations aren't essential.

Agreed again.

>I think it's possible that more details are also not
>essential and would like comments from others on
>possibilities as well as on the following argument.

Well, in general, anything that changes on the timescale of minutes 
or hours is probably not essential; loss of that should at worst 
produce a small retrograde amnesia (which is quite common, e.g. due 
to head trauma or anaesthesia, and poses no problems for survival).

>People seem to be able to survive seizures. As proof,
>consider all the people that survive seizures.

Yes, this is a very good example -- these screw up the brain in all 
sorts of transient ways, yet you can recover just fine with identity 
intact.

>The immediate problem is that if no ionic
>concentrations or ion channel conformations are
>scanned, then how will any activity start? Without any
>actual proof, I have a feeling that neurons such as
>pace-maker cells in the brain that have intrinsic
>activity will be enough to restart neural activity
>once the upload is running and allow the brain to
>'boot up' normally.

I think you're making it too complicated.  All neurons (and virtually 
all cells) are intrinsically active.  And by the time we have the 
technology to do such a scan, we'll know exactly what all the types 
of neurons are in the brain, be able to identify them, and know what 
their typical "default" state is.  We'll simply initialize the 
emulation to default states, turn it on, and let itrun -- this 
certainly will be a much smoother startup process than, say, 
recovering from a seizure.

>So that's my thinking on that. If I'm wrong, I'd love
>to hear why. Either way, I'd like to hear other ideas
>of what is and isn't needed. Other things to consider:
>proteins that have been made but are en route to their
>final site at the time of uploading, transcription
>activity in the nucleus, or general
>concentrations/amounts of enzymes and other second
>messengers and effectors within the neurons.

None of those worry me too much except one: gene activation states. 
It's possible that there will be genes which are 
activated/deactivated as an important part of the information-storage 
process, but which do not manifest in any more obvious phenotype. 
That would not be a show-stopper, but it would be a great nuisance, 
and I hope it's not true.  We do know that learning involves gene 
activation, but they're mostly genes known to result in protein 
synthesis, and this is probably just the machinery of forming new 
synapses (or strengthening existing ones, or retracting them, etc.) 
-- i.e., all things which ultimately result in changes in morphology. 
Or at least, that's my hope.

Cheers,
- Joe

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