I doubt most people reading the phrase "simulating a human brain" will make the distinction between simulating and emulating. The distinction is very technical and simply does not exist in the everyday use of the word "simulate".

As a layman, I imagine the simulation would have to account for any one of the thousands of different compounds and chemicals in the brain where emulating it might be easier but a lot less useful, like testing drugs on mice versus humans, never knowing what real difference will make an important one.

And yet the distinction is important as we are discussing a project on the very topic.

I don't think anyone playing SimCity thinks there's a whole real city running on their CPU. And certainly no one has a heart attack if you say SimCity is a simulation of a whole city.

If any model counts, then I can "simulate a human brain" as a sphere on a stick figure given five minutes in a physics sim.

We need to have some standard, and I would say the bare minimum is modeling each neuron in an ultra-simple way along with the connections between them.

Depending on what your doing modeling individual nerve cells may be pointless. For example, a stroke simulation may care a lot more about blood flow than communication between nerves.

It's certainly a useful project but don't call your blood flow simulation or vague activity map "simulating a human brain".

What if it turned out that neurons are highly redundant, and you can very effectively model network activity at a statistical level well above that of the individual neuron?

I've spent a few years studying biological modelling and simulation (of plants) but I've never heard of this distinction. Is it specific to neuroscience? What exactly is the "bottom" in a bottom-up approach?

> What exactly is the "bottom" in a bottom-up approach?

Great question (to which I have no idea what the answer is). It seems to me that the various attempts are trying to simulate sets of emergent behaviours at different levels of the brain's "stack". I guess, one way of determining the success of a "lower level" simulation/emulation, is the emergence of known "higher level" behaviours?

It's a distinction that physicists have brought into the field, the bottom refers to the lowest level of detail, usually cellular but sometimes molecular.

I don't think what you are saying is correct. Isn't an emulator something that takes the same inputs and produces the same outputs? I don't think "bottom-up" has anything to do with it.