Harnessing anesthesia and brain imaging for the study of human consciousness

Philosophers have been trying to solve the mind-body problem for hundreds of years. Consciousness is the core of this problem: How do subjective conscious sensations, perceptions, feelings, and thoughts arise out of objective physical brain activities? How is this subjective conscious world in causal interaction with the objective sensory and motor mechanisms of the brain and the body? Although we witness the seamless interaction of the mental and the physical worlds in our everyday lives, no scientific theory can yet fully describe or explain it. The hard problem of consciousness, the question why and how any brain activity should be accompanied by any subjective experiences at all, remains a mystery and a challenge for modern science. Anesthesia offers a unique and safe way to directly manipulate the state of consciousness and can, thus, be used as a tool in consciousness research. With neuroimaging, such as positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) performed at different states of consciousness, it is possible to visualize the state-related changes and pinpoint the brain structures or neural mechanisms related to changes in consciousness. With these tools, neurosciences now show promise in disentangling the eternal enigma of human consciousness. In this article, we will review the recent advancements in the field.