In both settings,once baseline EEG readings are established (30 minutes), EEG data will be recorded and a sleep mask will be applied to the patient for one hour. After one hour (90 minutes), EEG data will be recorded and the sleep mask will be removed. After another hour (150 minutes), EEG data will be recorded and the mask reapplied. After another hour (210 minutes), EEG data will be recorded and the mask removed. The levels/doses of anesthetic agent at each time point will also be recorded.