**Stimulus-Evoked Directional Field Potentials to Guide Subthalamic and Pallidal DBS for PD** This study aims to improve **Deep Brain Stimulation (DBS)**, a treatment for **Parkinson’s Disease (PD)** by understanding how DBS changes brain activity and guiding therapy. DBS involves placing electrodes in the brain to help with motor symptoms like tremors and stiffness. This study will look at different ways to target the brain with DBS to see which works best. Participants will have surgery and then be monitored over 16 months to measure changes in movement and how they feel. **Key Points:** - **Study Duration**: Participants will be involved for 16 months after surgery. - **Visits**: Regular check-ups every 4 months for assessments, plus one final visit. - **Eligibility**: Participants must be 18 or older, have advanced PD, and meet other health criteria. Participants will need to be available for follow-up visits and willing to undergo surgery and evaluations. This study does not cover costs not included in routine DBS care.