i don't think it would be so simple and i don't think you can abstract neurons so hard, there are extrasynaptic receptors that react to concentrations of neurotransmitters outside synapses, and there are some neurotransmitters that leak out of synapses. thousands of leaking synapses can contribute to activation of some random receptor, or more than one this way. some other receptors are extrasynaptic by default and don't really have synapses, neuropeptides work like this but not only these. for gasotransmitters, effectively there's no concept of synapse. i don't think you can abstract all neurotransmitters to some one chemical messenger either, there are different ones with different half-lives, different diffusion rates, different metabolites some of which work in completely different ways. (steroids, neuropeptides, gasotransmitters, whatever lipids go into cannabinoid system, it's not just monoamines/glutamate/GABA/acetylcholine).

some receptors take multiple inputs, there are NMDA receptors that really only fire when glutamate and glycine both bind to it, and only after AMPA receptor nearby opens up first. we already know these things are important in forming of memories so it's probably a big deal. some of these receptors are ion channels, and some of these are important especially intracellular calcium

[–] porous_grey_matter@lemmy.ml 2 points 10 hours ago (1 children)

That makes their napkin calculation extra generous, and us even less likely to be near being able to stimulate such a thing.

[–] fullsquare@awful.systems 1 points 9 hours ago (1 children)

at minimum this requires additionally keeping position of neurons, modelling concentration of any neurotransmitters and their diffusion (taking into account shape of cells around) and their degradation products, some of which are active on their own. whatever set of interactions might be between neurons, it'll probably make it changing with time and probably not sparse (information exchange isn't just packaged neatly within synapses)

[–] porous_grey_matter@lemmy.ml 1 points 8 hours ago* (last edited 8 hours ago) (1 children)

Yeah, maybe, all those things could be necessary for sure. It's possible that our brains aren't the exact most optimal way of structuring such a thing, and it's not guaranteed that the best way to replicate it is to stimulate it. It's also plausible that there are calculations which capture a good deal of the complexity of the relative positions of neurons in simpler terms. Maybe there are way more complications than that. Maybe some of them work against each other in our brains and it would be better to leave them out of a simulation. There are many orders of magnitudes of unknowns. But it seems really likely that it's at least as complicated as what the earlier poster described. And I think that's quite a strong position already for most practical arguments about it.

[–] fullsquare@awful.systems 1 points 8 hours ago* (last edited 8 hours ago)

it's a guess of what can be abstracted away and what has to remain. i'd just add that evolutionarily, peptide signalling is older than synapses so these, or something that works like these, probably can't be just left out of the picture, and there's a couple of processes that seem important that depend on them (you can live normal life while packed full of naloxone, which blocks activity of opioid peptides, but this probably won't work with, say, orexin which is important for sleep/wake cycle)