tACS Modulates Speech and Cognitive Impairments in People With PD by Targeting the Medial Frontal Cortex

This clinical trial aims to study whether transcranial alternating current stimulation (tACS) applied to the medial frontal cortex (MFC) can improve speech and cognitive function in people with Parkinson's disease (PD), and to evaluate the safety of tACS. The main goals are to answer the following questions: 1. Can tACS stimulation of the MFC improve executive functions in people with PD (such as reasoning, planning, inhibition, and complex problem-solving)? 2. Can it improve the integration of auditory information and speech motor control during communication? Researchers will compare the effects of real tACS versus sham (placebo) stimulation to see if real stimulation leads to better speech and cognitive outcomes in PD patients. Participants will: 1. Receive one extra 20-minute session of either real or sham tACS each day for two weeks 2. Attend clinic visits before stimulation, right after the 2-week period, and again at 1 month and 3 months for assessments and tests 3. Have their executive function scores, speech performance, and related brain activity recorded