UNderstanding CONSciousness Connectedness and Intraoperative Unresponsiveness Study

Inclusion Criteria:

* Age 18-40
* In good health, determined by the PI on the basis of medical history and a standard assessment for anesthesia to be documented as part of the study record
* Right handed, to standardize for asymmetry in brain functions

Exclusion Criteria:

* Adults \<18 years old or \>40 years old
* Pregnancy confirmed on pregnancy test on day of sedation
* Contraindication to anesthesia or allergy to study drug
* Difficult anesthesia: American Society of Anesthesiologists Physical Status greater than 1, per the discretion of the PI. Examples of ASA status include, but are not limited to:

  * Any systemic disease present, such as diabetes, cardiac, pulmonary, or other acute or chronic disorder, or history of smoking
  * Narrow angle glaucoma
  * Abnormal airway examination
  * Any abnormality on medical history and physical examination
  * Snoring or sleep disorders including apnea
  * Antecedent pulmonary aspiration risk (e.g., history GI reflux, heartburn, hiatal hernia)
  * Adverse reaction or allergy with anesthesia or other sedatives
  * Chronic medication use
  * History of difficult anesthesia, laryngoscopy or intubation
  * Family history of difficulty with anesthesia or sedation
  * History of vertigo, nausea or vomiting after anesthesia
* BMI \> 35
* Contraindication to HD-EEG, TMS or MRI for relative parts of the procedures. MRI exclusion criteria: presence of metallic or electronic implants; history of claustrophobia. TMS exclusion criteria: Presence or history of medical conditions that could increase the chance of seizures (e.g. - stroke, aneurysm, brain surgery, structural brain lesion) cranial metal implants; structural brain lesion; devices that may be affected by TMS (pacemaker, medication pump, cochlear implant, implanted brain stimulator); history of head trauma with loss of consciousness for greater than 5 minutes; family history of seizures; history of antecedent mood disorder.
* Exclusion from Dexmedetomidine:

  o Resting heart Rate\<60 bpm
* Exclusion from Propofol:

  o Reported egg allergy
* Exclusion from Ketamine:

  * History of post-operative nausea and vomiting
  * History of motion sickness

Additional exclusion criteria on the day of sedation:

* Anything to eat or drink for the preceding 8 hours
* Any use of over-the-counter or recreational drugs (including alcohol or tobacco) within the preceding 24 hours
* Any use of sedative or sleep agents within the preceding 24 hours
* Recent change in health, including cough, cold, or fever
* Exposure to anesthesia or sedation in the last 6 days