Simple thought experiment. Imagine that I undergo some exotic surgery in which a few of my brain cells get replaced with a tiny computer emulating exactly the behavior of those cells. Same connections, same reaction to stimuli, same timing.
The next day, a few more cells get replaced, and so on and on until my brain is completely made of silicon and firmware.
Would I still be intelligent at this point?
If no, care to guess when and why I ceased to be?