[Anesthesia, awareness and wakefulness].

Drugs used in anesthesia do not always produce the expected neurophysiological results. By studying those cases in which the reappearance of intraoperative awareness is most common, an attempt was made to estimate how many and which levels of cerebral function could be identified. Four levels were recognised: awareness with or without memory, and wakefulness with or without dreams. These conditions are related to greater or lesser cortical activity. They can be identified using Tunstall's technique and by carefully interviewing the patient immediately after the operation.