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Comment by RaftPeople | Hacker News Reader

> The hardware of one GPU can be used to simulate billions of neurons in realtime.

You mean simulate billions artificial neurons, right?

You can't simulate a single biological neuron yet because it's way too complex and they still don't even understand all of the details.

If they did have all of the details, at minimum you would need to simulate the concentrations of ions internally and externally as well as the electrical field around the neuron to truly simulate the dynamic nature of a neuron in space and time. It's response to stimulus is dependent on all of that and more.

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Depends a bit on how certain you are on your preferred answer to the question: is the brain analog or digital? If you think it is predominantly digital, quite a lot of the details of the biochemical mechanisms don't matter. If you think it is predominantly analog, they matter hugely.

Do any serious theories on the brain being predominantly digital hold any water with neuroscientists? I feel like it's fairly well accepted that the brain isn't digital even just with what we do understand about neurons?

I don't think it's possible to tell at this point.

If you looked at the operation of a digital computer, you'd find an analog substrate, with some quite interesting properties. Deciding whether the analog substrate is an important semantic element of how the computer worked, or whether its operation should be understand digitally, is as much a (research-driving) leap of faith as anything else.

That's actually a pretty convincing point. If all we were able to understand was the flow of electrons in a transistor and not how they were connected, we wouldn't necessarily be able to conclusively claim that digital computers were indeed digital.

Action potentials are digital. Once the neuron hits the trigger threshold, the spike happens at the same amplitude every time.

The process by how the neuron determines whether it's time to fire or not is almost grotesquely analog, in that it is effected by a million different things in addition to incoming spikes.

How much of each process matters for what is the mind-generating part of the brain's work? We don't know.

Myelination (which allows very fast, and digital, communication between neurons) is universal in vertebrates, which points to it being important for intelligence.

As a counterexample, we have cephalopods, which accomplish their impressive cognitive tasks using only 'slow' neurons; they get around the speed limit by having huge axons, which reduce internal resistance. So we know that digital transmission isn't necessary for intelligence, either.

The nature of cognition is a fascinating subject, isn't it!

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