It's interesting that we had a very similar discussion here minus the actual quantum mechanics. At least intuitively it seems like physical change is what leads to consciousness, not simply the possibility or knowledge of change. One possible counter-argument to consciousness being dependent on decoherence is the following: What if we could choose whether or not, and when, to decohere? For example, what if inside Schroedinger's box is a cat embryo that will be grown into a perfectly normal immortal cat if nucleus A decays, and the box will open if nucleus B decays. When the box opens, is there no cat, a conscious cat, or a cat with no previous consciousness? What if B is extremely unlikely to decay but the cat can press a switch that will open the box? It seems non-intuitive that consciousness should depend on what happens in the future, outside your environment.