Anesthesia unlocks a more primitive level of consciousness

April 5, 2012

If you've ever been put under anesthesia, you might recall a disoriented, almost delirious sensation as you wake back up. That feeling is more than simple post-surgery confusion: it's actually the brain reverting to a more primitive evolutionary state.

That's the finding of researchers from UC Irvine and Finland's University of Turku, who used positron emission tomography, or PET, to image twenty research volunteers' brains as they reawakened from anesthesia. They found that consciousness - in this case, the patients' ability to perform a motor response when commanded to - first emerged as a "core network" of the brain reactivated. This network included the brain stem, thalamus, hypothalamus, and other ancient parts of the brain.