CMN LIFU for Enhanced Glymphatic Clearance in Amyloid-Positive MCI

The goal of this clinical trial is to learn if a wearable ultrasound device, called ATTN201, is safe and easy to use. The study is for adults ages 65 and older who have mild cognitive impairment (MCI) and a buildup of a protein called amyloid in the brain. Amyloid buildup is an early sign of Alzheimer's disease. The ATTN201 device sends low-intensity sound waves to a deep area of the brain that helps control sleep. The aim is to boost deep-sleep brain waves. These brain waves may help the brain clear away waste, including amyloid. The main questions it aims to answer are: 1. What, if any, issues do participants have when using the ATTN201 device? 2. Can participants complete the full study schedule? Researchers will compare focused ultrasound to unfocused ultrasound. Unfocused ultrasound is a look-alike treatment. It feels and sounds the same but is not aimed at the brain target. The comparison will show if the focused treatment changes sleep brain waves, blood markers of Alzheimer's disease, or memory and thinking. Participants will: * Visit the study site for memory and thinking tests, blood draws, a health check, and MRI scans of the brain * Record their sleep at home for at least 5 days with a sleep diary, a watch-like sensor, and a headband that measures brain waves * Be assigned by chance to focused or unfocused ultrasound * Take part in 10 nap sessions over 2 weeks while wearing the device, at the study site or at home * Return for a final visit to repeat the first tests, and may return for an optional visit 3 months later