Alzheimer's disease (AD) is a brain disorder that gradually impacts cognitive functions such as memory, thinking, and daily functioning. Gamma oscillations are a type of brain activity thought to play a role in memory and cognition (thinking abilities). In AD, these oscillations are impaired - meaning they are smaller and slower than the brain waves observed in healthy individuals. Research suggests that enhancing these brain waves may help slow the progression of AD. This research is investigating a technique called deep brain stimulation (DBS) of the pedunculopontine nucleus (PPN) as an experimental intervention. An electrode will be implanted in the PPN and deliver mild stimulation over the course of a 12-month period. As a novel intervention, the priority of the study is to determine if DBS-PPN is a safe and feasible intervention for mild-AD. Additionally, the study investigators are evaluating whether DBS-PPN can increase natural gamma oscillations in ways that improve memory and cognition. The insights from this study will guide the design of an accessible larger trial to more definitively assess how effective DBS-PPN could be as a treatment for AD. Participants will: * Undergo a 12-month experimental intervention involving DBS of the PPN. The procedure for implanting the DBS device takes approximately 2-3 hours under general anesthesia, followed by an overnight stay in the hospital for safety monitoring. * Be required to attend regular appointments every 3 months from DBS implantation for the duration of the study. The follow-up visits will include safety and feasibility monitoring, brain scans (EEG and MEG), and cognitive assessments/questionnaires. * Participants' caregiver will also complete questionnaires about their cognition, functioning, and overall health at the follow-up visits.