Interventions for Postoperative Delirium: Biomarker-3

Inclusion Criteria: * Cohort 1: Age ≥65 years * Cohort 2: Age ≥60 years * Anticipated length of hospital stay of at least 2 days after surgery that occurs under general or neuraxial anesthesia * Written Informed Consent for potential participation prior to surgery Exclusion Criteria: * Contraindication to EEG * Unable or unwilling to attend the follow-up appointments * Documented history of dementia * Deemed incapable of providing consent by surgical team * Residing in a nursing home * Undergoing intracranial surgery * Unable to complete neurocognitive testing due to language, vision or hearing impairment * Unable to communicate with the research staff due to language barriers * For optional MRI portion of the study: Contraindication to MRI (e.g., implanted devices not safe for MRI studies, claustrophobia, unable to lie flat or still)