Parkinson's disease (PD) is a condition that makes moving and thinking harder. People with PD often have "OFF-time," when their medications don't work well, which affects their life and mind. Partnered Dance Aerobic Exercise (PDAE) is a fun dance activity that helps reduce OFF-time and improve thinking skills. PDAE involves dancing with a partner and thinking about steps and patterns. It has been shown to help for at least a month after stopping the sessions. Researchers want to see if PDAE is better than just walking in protecting brain cells and improving symptoms. They will study people with PD for 16 months. Participants will be randomly assigned to either PDAE or walking. The study involves taking two classes per week for the first three months, then once a week for 13 months. Participants will have appointments at the start, after three months, and at the end of the study to check their progress through tests and a brain scan.

• Study lasts for 16 months with regular classes.
• Participants need to be okay with being randomly assigned to a group.
• Eligible if older than 40, can walk 10 feet, and have certain health scores.