Gamma Induction for Alzheimer's Disease

This is an interventional, sham controlled, double-blind study in patients with early to moderate Alzheimer's Disease (AD). The study will enroll approximately 55 individuals with amyloid positive Mild Cognitive Impairment (MCI) or AD. Each subject will undergo a 1-2 visit screening period consisting of a physical and neurological exam, medical history and medication review, safety questionnaires, and cognitive testing. Each subject will then undergo 5-7 baseline visits including neuropsychological testing (memory and thinking tests), amyloid Positron Emission Tomography (PET) imaging if one is not available or it has been greater than 6 months, tau PET imaging, tACS-EEG (transcranial alternating current stimulation and electroencephalogram) assessment, TMS-EEG (transcranial magnetic stimulation and electroencephalogram) plasticity assessment, functional magnetic resonance imaging (fMRI), blood and saliva sample collection, and optional lumbar puncture (LP). Participants will be randomly assigned to one of four groups: stimulation for 2 weeks or 4 weeks, once a day or twice a day. One of the groups is a sham group. This means that this group will not receive actual tACS. Each session will be one hour of either individualized gamma-frequency (40 Hz) tACS or sham tACS, depending on the assigned group. Subjects will be assessed for any side effects before and after each session and complete a short memory and thinking test either daily or weekly. At the end of the daily sessions, 5-7 follow up visits will include a repeat of the baseline measures including amyloid and tau PET scans. Long-term follow-up visits will include an EEG, cognitive testing and an amyloid PET scan. Participants will be randomly assigned to a repeat amyloid PET scan at either 2, 4 or 8 weeks after the last scan. The PET imaging studies will be conducted at Massachusetts General Hospital.