Sleep and Performance

This research is being done to apply new, contrast-free MRI (Magnetic Resonance Imaging) methods to understand the brain's waste clearance system (the "glymphatic" system) in younger adults. The Investigators hope the study will show how the different brain regions are involved in maintaining memories and how poor sleep affects these regions and our ability to remember. The Investigators will test whether the Wireless Interface Sensor Pod (WISP) improves brain function after poor sleep. The WISP is a headband that combines tracking brain waves and transcranial electrical stimulation (TES) to monitor and improve slow wave sleep and glymphatic clearance. IParticipants will be asked to: * Complete 4 in-person study visits (1 per week) over 4 weeks at the Diagnostic Imaging Sciences Center (DISC), located at the University of Washington Medical Center at Montlake, Seattle. Each visit will last 2 hours and includes a 1 hour MRI and 1 hour of cognitive testing. * Complete a daily journal about sleep, daily habits, etc. * The night before each of the four study visits, participants will sleep while wearing the WISP headband. * For two of these nights, participants will sleep only 3 hours prior to normal time of awakening. The WISP will deliver a small electrical current for one night and not for the other night, but participants will not know which. * For the other two nights, participants will follow a normal sleep schedule. The WISP will deliver a small electrical current for one night and not for the other night, but participants will not know which.