[Animats]

That problem has been overcome.[1]

This is a neat result. This research started with the differential equation model of a neuron and tried to train various neural nets to get the same result to within 99%. They succeeded. Worst case took an 8-layer net with 256 elements per layer. See Fig. 4. So, 10 billion elements for a squirrel. Not that big by current standards.

It's not clear that a model which tracks the biological neuron that accurately is needed. They discuss simpler models that are almost as good.

Low-end mammal brains should be buildable right now. It's not a hardware limitation.

[1] https://www.sciencedirect.com/science/article/pii/S089662732...