I think the underlying assumption you're making is that a sufficiently powerful computer could emulate the chemical processes in the brain, and that this is the

I think the underlying assumption you're making is that a sufficiently powerful computer could emulate the chemical processes in the brain, and that this is therefore equivalent to running a brain on a computer, decoupling cognition from brain meat. The problem is there are hard physical limits you run into in computation - it's more efficient to just do the chemistry than it is to simulate it. Our meat brains might be more efficient in terms of density and power efficiency than any physically feasible digital computer. Further, computing power can't be increased arbitrarily, especially when networks and switching come into play. Even if your simulated brain worked out how to improve itself, the resource cost to actually do so might be prohibitively high.