Deep brain stimulation (DBS) is a treatment where small electrical signals are sent to a part of the brain called the dorsal subthalamic nucleus (STN). It's used to help with the movement problems in Parkinson's disease (PD). Sometimes, these signals can affect other brain areas, making it harder to think clearly. This study will test if adding low frequency signals (called Low Frequency Stimulation (LFS)) to another part of the STN can help without causing thinking problems. They will still use the regular high frequency signals (High Frequency Stimulation (HFS)) at the same time.

• The study is for people aged 18 or older who already have the Boston Scientific VerciseTM DBS device.
• Participants will need to complete thinking tests in English.
• Those unable to provide consent, pregnant women, prisoners, and people with certain mental health scores are not eligible.