maybe just the ability for the consciousness to express itself in a way humans can understand vanishes. ??

First, I don't know which is the difference/connection between real and possible alternatives. By real you mean plausible? Secondly, consciousness goes away even though those many _relatively simple_ interactions are still there. So, I'd say, that we don't really know for sure that consciousness is not there when worms are eating our brains.

Consciousness is a subjective phenomenon. That's what makes it impossible to study directly, without relying on reports. And that's what separates it from those _relatively simple_ interactions which we can model and study experimentally.

It does not. If I think of something sad, molecules flow through my body. If I eat icecream, I remember something sad. The problem of mental causation. Unsolved. There're other problems, just as deep.

Physical causation in on one side of the deep. Phenomenal experiences are on the other side.

Good read: Facing Up to the Problem of Consciousness - http://consc.net/papers/facing.html