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