Neurostimulation for Cognitive Enhancement in Alzheimer's Disease

The hallmark of Alzheimer's Disease (AD) is cognitive decline with varied associated symptoms and signs. Unfortunately, there is no cure as yet for AD. Available treatments, including 5 FDA-approved medications, have limited efficacy in terms of slowing pathological progression or controlling the symptoms and signs of cognitive decline in AD patients. Given the high burdens and costs of AD, and the therapeutic limitations, the development of novel treatment approaches for AD is of the highest importance for patients, families, medical providers, and society. This randomized controlled trial will determine if innovative, low-risk neurostimulation at home for 6 months can improve cognitive performance and symptoms in patients with mild to moderate AD. The primary objective is to determine the effects produced by 6 months of active tDCS or sham delivered over dorsolateral prefrontal cortex (DLPFC) in home settings on global cognitive performance (assessed by ADAS-Cog test - primary outcome), and secondarily on executive control/spatial selective attention (Eriksen Flanker Test), depressed mood (Geriatric depression scale), quality of life (Quality of Life Questionnaire-Alzheimer's Disease), and patient satisfaction with both the device and procedure (Neurostimulation User's Survey), in mild-to-moderate AD patients (n=100). The investigators also aim to determine functional and structural brain connectivity/network changes in response to the study intervention using functional Magnetic Resonance Imaging (fMRI; during rest and during executive function tasks), diffusion-weighted imaging (DWI), and multivariate covariance-based analytic approaches. Lastly, the investigators aim to examine time characteristics (durability) of the tDCS behavioral and neuroplasticity effects for up to 3 months following the intervention period. The intervention will consist of remotely supervised active tDCS stimulation and sham tDCS stimulation over the area of the dorsolateral prefrontal cortex, applied at home for 30 minutes 5 times per week for 6 months. Participants randomized to the active tDCS will receive at each application 30 minutes of direct current stimulation at the intensity of 2 mA. Participants randomized to the sham group will receive sham tDCS which consists of current ramped up to 2mA over 30 seconds, ramped down over 30 seconds and stay at 0 current for the remaining time of the 30-minute application.