Generally, the people doing brain simulations like to claim that they can use a massively reduced representation (little more than a graph model that pushes signals around with some constants) and yet, somehow, the simulation is inherently capable of reproducing something complex about thought. I'm not sure how they get to this conclusion, but it's a massive reductionism. It would be nice if it were true- it would mean that for a reasonable expenditure, we could build a machine that, basically, "thought" and had a "mind" and we could convince ourselves that it was "living" much like we think of other humans.

To date nobody has come up with a really compelling disproof that they are more or less correct- thought and mind seem to be best explained as "emergent behavior of a complex system".

Now, whether can we bootstrap a thinking mind by running complex simulations on computers remains to be seen. I'd like to believe there is some interesting physics going on in brains we can't simulate with straightforward physical models, but there really isn't any good evidence for that.