How can we find the neural correlate of consciousness?

There are two concepts of consciousness, access consciousness and phenomenal consciousness. But just as the concepts of water and H2O are different concepts of the same thing, so the two concepts of consciousness might come to the same thing in the brain. Some recent papers by Crick and Koch raise issues that suggest that these two concepts of consciousness might have different (though overlapping) neural correlates, despite Crick and Koch's implicit rejection of this idea.