[katmannthree]

I believe we've been able to model the processes behind neural firings for quite some time now, the issue is more mapping between that micro-scale understanding of how each individual piece in a 10^10 piece puzzle with 10^15 edges affects the macro-scale emergent properties of said puzzle. It's less a lack of understanding of the processes and more a complexity so great that it exceeds the grasp of our best modeling tools thus far.

We can barely model the humble nematode c. elegans with its 330 neurons.

[SubiculumCode]

Our biophysicalmodesl of neurons are actually woefully simplistic. https://journals.physiology.org/doi/full/10.1152/jn.00360.20...

[katmannthree]

Yes. The simple models are simple, the fast and large and useful models are simple. We have a lot of in vitro observations which can contribute to smaller, slower and more accurate models as your linked article mentions, observations which generally are ignored as being nth order effects when people are trying to make models which have a low enough computational complexity as to be useful.

What is not missing is metaphysical quantum woo[0]. We can, have, and do observe how neurons and synapses function; the issue is that the computational complexity with current approaches is great enough to make complete neurological modeling of a microscopic worm with under a thousand total cells difficult.

[0] and even if you want to take those effects into account in your electrochemical models, all they do is turn them into stochastic models. there is exactly zero evidence of that randomness being of any real value to the thing we care about, which is the emergent macro scale properties of these systems.

[taneq]

Can we barely model it yet? I thought they weren’t at the point of getting able to simulate any actual work behaviours?

[katmannthree]

We can model neural activations but the whole-cell body simulation was still unstable last I checked (admittedly a year or so ago)

[taneq]

Does the modeled activity track any real world measurements, though? If we're going to claim any real veracity from a simulation then we need to crosscheck it against real measurements, right?

[katmannthree]

I believe they’ve attempted to measure synapse weights from real worms for training the net, the firings themselves are just basic electrochemistry.

[taneq]

'Attempted' implies 'not succeeded', though? And 'just basic electrochemistry' triggers a massive "is it, though?" response. Sure, we know what theory tells us, I want to know if observations align with theory.

[katmannthree]

Succeeded within what level of precision? The project is called OpenWorm, they have hydrodynamic models for macroscale cellular behavior and electrochemical simulations for modeling ion channels needed for the neural network. I don't have a reference handy but you should be able to find ample papers discussing accurate electrochemical modeling of synapses. The issue is that the models are complex enough that simulating a couple hundred neurons is expensive. As far as having accurate synaptic data so that they're simulating a specific worm rather than a random one pulled out of the æther, I believe that's still a work in progress.