Continuous Measurement of Glymphatic Activity in the Human Brain During Sleep-Wake States

Inclusion Criteria: 1. Participants must have a Montreal Cognitive Assessment (MoCA) score at least 26. 2. Participants must have a Geriatric Depression Scale (GDS) 15-item score of 4 or less. Exclusion Criteria: 1. Participants with a formal diagnosis of any sleep disorder (e.g., sleep apnea on positive-airway-pressure (PAP) therapy, insomnia, restless leg syndrome, circadian rhythm sleep disorder, parasomnia). 2. Participants with a history of significant neurological disease or history of epilepsy. 3. Participants with cardiovascular disease or cardiovascular risk factors (smoking or hypertension). 4. Participants with diabetes. 5. Participants with traumatic brain injury, or serious mental illness including bipolar disorder, schizophrenia, major depressive disorder or post-traumatic stress disorder. 6. Participants who have taken in the past 30 days prescribed or over-the-counter (OTC) stimulants, sleeping medications, or psychiatric medications including antidepressants. 7. Participants who consume more than 400 mg/day of caffeine. Participants will be required to not consume caffeine beginning 12pm on the day-of the sleep study. 8. Female Participants who consume more than 3 alcoholic drinks on any day or more than 7 drinks per week. Male participants who consume more than 4 alcoholic drinks on any day or more than 14 drinks per week. 9. Participants who have or will have travelled across time zones 10 days prior to either Study Visit or whose first and second Study Visits span Daylight Savings time change (November 6, 2022). 10. Participants with travel plans or conflicts that would prevent them from either Study Visit. 11. Participants who are enrolled in other research studies and are receiving an investigational drug within 30 days of the planned start date. 12. Participants who have any condition that, in the opinion of the Sponsor Principal Investigator, would compromise the well-being of the participant or the study or prevent the participant from meeting or performing study requirements. 13. Participants with absolute or relative contraindications to MRI imaging based on current up-to-date screening questionnaires including claustrophobia, inability to lie still on their back for 30-45 minutes or require sedation prior to the MRI. 14. Participants with a head circumference greater than 60 cm that would prevent use of a high-resolution 64 channel MRI head coil required for this study 15. Participants who have a pre-planned surgery or medical procedure that would interfere with the conduct of the study. 16. Participants who have an implanted medical device or contraindications that would exclude MRIs 17. Participants with a serious infection requiring medical attention in the past 30 days