Currently it is unknown how the human brain reorganizes its network organization to generate conscious experience and cognitive activity after a period of unconsciousness. Therefore, the purpose of this study is to assess how cognitive activity is reconstructed after general anesthesia. The investigators hypothesize that the brain's transition from unconsciousness to consciousness and full cognition is a complex process that occurs over an extended period of time. Specifically, the investigators hypothesize the following order of cognitive reconstitution: responsiveness to command, attention, complex scanning and visual tracking, working memory, and executive function.

Volunteers will be healthy participants who are anesthetized with commonly used anesthetic drugs as well as a non-anesthetized group to control for circadian influences. A total of 60 subjects will be recruited for this study. All subjects (male and female) will perform basic tests for cognition on a laptop computer at 30-minute intervals during this study. The testing battery to be administered was assembled to assess multiple cognitive functions in order to determine whether and how cognitive processes return to baseline function. Electroencephalogram (measuring brain electrical activity) data will be monitored and recorded during both anesthesia and cognitive testing, for subsequent analysis.

This study is significant because it could lead to a better understanding of the neural correlates of human consciousness, as well as normal and abnormal conscious state transitions (including barriers to such transitions).

Inclusion Criteria:

• Healthy 20-40 year old volunteers,
• American Society of Anesthesiologists Physical Status I or II (i.e., healthy),
• Body mass index < 30 kg/m2,
• Easily visualized uvula,
• With anticipated equal recruitment of males and females.

Exclusion Criteria:

• Physical signs suggestive of difficult airway (e.g., mouth opening <3cm, short distance between the chin and neck, poor mandibular subluxation, thick neck),
• History of obstructive sleep apnea,
• Reactive airway disease,
• Neuropsychiatric disorders,
• History or current use of psychotropic medications,
• Current tobacco and alcohol use,
• History of hypertension or current medication for blood pressure control, cardiovascular disease or arrhythmias,
• Positive urine toxicology screen,
• History of reflux,
• Pregnancy,
• Family history of problems with anesthesia (including but not limited to malignant hyperthermia),
• Sleep disorders,
• History of postoperative nausea/vomiting or motion sickness,
• Allergy to eggs, egg products or soy.