Three neuroscientists have said that the brain under general anesthesia isn't "asleep" as surgery patients are often told -- it is placed into a state that is a reversible coma.They have published an extensive review of general anesthesia, sleep and coma, in the Dec. 30 issue of the New England Journal of Medicine. This insight and others reported in their review article could eventually lead to new approaches to general anesthesia and improved diagnosis and treatment for sleep abnormalities and emergence from coma.The researchers explain that a fully anesthetized brain is much closer to the deeply unconscious low-brain activity seen in coma patients, than to a person asleep. Essentially, general anesthesia is a coma that is drug-induced, and, as a consequence, reversible. The states operate on different time scales -- general anesthesia in minutes to hours, and recovery from coma in hours to months to years, if ever. The study of emergence from general anesthesia and recovery from coma could help to better understand how both processes occur. Understanding that these states have more in common with each other than differences -- that they represent a continuum of activity with common circuit mechanisms being engaged across the different processes of awakening from sleep or emerging from coma or general anesthesia -- "is very exciting, because it gives us new ways to understand each of these states," says study co-author, Dr. Nicholas D. Schiff, a professor of neurology and neuroscience at Weill Cornell Medical College and a neurologist at NewYork-Presbyterian Hospital/Weill Cornell Medical Center. Co-authors of the study are Dr. Emery Brown of Massachusetts General Hospital, Massachusetts Institute of Technology and Harvard Medical School, and Dr. Ralph Lydic from the University of Michigan.