The Blacked Out Brain : Neural Mechanisms of Unconsciousness in General Anesthesia and Disorders of Consciousness

Finding the neural mechanisms of unconsciousness is a pursuit with significance to both the scientific study of consciousness as well as for the improvement of clinical diagnosis of patients with severe structural brain damage that has resulted in disorders of consciousness (DOC), such as coma or vegetative state . This literature review gives an account for what consciousness studies have contributed to the understanding of the neural mechanisms of unconsciousness, focusing on experiments using anesthetic agents to investigate the loss and return of consciousness. Mechanisms that frequently correlate with the loss of consciousness are modulation of the brainstem, the thalamus, and the cortex, but different anesthetic drugs act on different areas. According to a bottom-up approach unconsciousness can be induced by sleep-circuits in the brainstem, and according to a top-down approach unconsciousness can be induced by cortical and thalamocortical disruption. But the mechanisms involved during loss of consciousness are not the same as for return of consciousness, and this paper includes evidence for the mechanisms involved during the return being closer to what research should be further investigating. The mechanisms involved in return from anesthesia-induced unconsciousness resemble those mechanisms involved in recovery from DOC. Studying mechanisms of unconsciousness can further our understanding of consciousness, as well as improve the diagnosis and treatment of patients with DOC.