The goal of this clinical trial is to learn about the ability of non-invasive brain stimulation during sleep to enhance people's deep sleep and its potential benefit on memory in people with mild cognitive impairment via home use sleep therapy device (SleepWISP) as well as learn about biomarkers associated with Alzheimer disease (AD). The clinical trial aims to answer the following main questions: 1. Whether the non-invasive transcranial electrical stimulation (TES) delivered by SleepWISP could provide short-term enhancement of deep sleep in a single night in the target population. 2. Whether TES delivered by SleepWISP could enhance deep sleep over multiple nights in the target population. 3. Whether enhance on deep sleep could improve memory performance in the target population. Participants will be asked to wear non-invasive and painless devices that record their brain activity during sleep along with an actigraphy watch that measures their movement throughout the day. In addition, blood samples or nasal swab assays will be collected from participants multiple times during the study.