Working inward from the sense organs, neuroscientists have begun to isolate those brain areas and processes important for consciousness. After starting at the back of the brain, where most perceptual processing takes place, we have now made it all the way to the front. We know the basic wiring of the brain, and for the first time, we have theories of how it works as a whole. Yet a troubling problem remains. The ability to actually see the brain performing its different cognitive tasks, together with the converging data from neurophysiology and neuroanatomy, has led to the theory that conscious brain states involve large parts of the brain's cortex—its wrinkled outer covering—supported by activity in many subcortical structures, working together in synchronized rhythms. We now have our first detailed neurophysiological theories of consciousness. These theories are still operating from the outside, however. All of the current research techniques leave the scientific observer of the brain locked out of the experience the subject herself is having. Using their new imaging technologies, the scientists can observe all sorts of brain activity, but it seems they can never detect the most crucial properties of conscious states, the ones we are aware of. If someone is looking at a blue sky, for instance, the scientists monitoring her brain can't detect anything blue. How, then, can we ever be certain that these synchronized brain states are the conscious mental events we experience? The possibility still seems entirely open that our conscious mental lives reside elsewhere, in some other realm.
William Hirstein, Mindmelding: Consciousness, Neuroscience, and the Mind's Privacy