Here's a roundtable that gives an interesting high-level overview of a couple of points:
First, Joseph Bogen, a neurologist, gives us possible levels at which the brain could produce consciousness: sub-cellular, cellular, circuit, systems, the whole brain, or brain interacting with larger systems (other brains).
Second, we get a quick face-off at the end with Stuart Hameroff mentioning something like Chalmers's view that "proto-consciousness" is a fundamental property of subatomic particles (like spin or mass), a view that Christof Koch dismisses as "a mystical statement that's totally untestable." It's quickly clear that this is again a face-off between philosophers (like Nagel, Chalmers, and McGinn) who want to deal with the "hard problem" of how to make the conceptual leap between the physical and the mental and the engineering problem of what's going on in the brain (whether analyzed purely at the biological level or also at the functional level) when consciousness occurs. Koch argues that these philosophical questions, still unanswered after many years of consideration, are simply not helpful in achieving the progress that's being made on the neurological side. Hameroff argues that you still need to answer the philosophical questions in order to understand consciousness and not just know the correlations between consciousness and brain activity.