Neuroscientists are using anesthesia to study consciousness in a way that seems related to higher order theories of consciousness. The conclusion so far: "consciousness emerges from the integration of information across large networks in the brain":
Over the past few years, other EEG studies have supported the idea that anesthesia doesn't simply shut the brain down but, rather, interferes with its internal communication. Mashour's research, for instance, has shown that feedback between the front and back of the brain is interrupted during general anesthesia, leading to a disconnect between different brain networks. That feedback is thought to be important for consciousness.
"What we find is that the anesthetized brain is still very reactive to stimuli," he says; both EEG and functional magnetic resonance imaging (fMRI), an indirect method of measuring brain activity, show response to light and sounds. But somehow that sensory information is never processed and integrated into the type of activity necessary for conscious awareness.