Safely Switching Consciousness Off and On Again: Scientific American

Safely Switching Consciousness Off and On Again: Scientific American: When consciousness was lost after anesthesia was initiated—that is, when the patients no longer opened their eyes following the command—the cortical EEG changed dramatically, switching from low amplitude and irregular activity into readings dominated by large and slow brain waves that occur about once every second. Such so-called delta band activity is characteristic of deep sleep. Furthermore, the complexity of the cortical EEG signal decreased significantly when patients stopped responding. None of these changes occurs in the thalamic electrode at the time that consciousness is lost.