Parkinson's disease (PD) is a condition that affects movement and thinking. People with PD often experience "OFF-time," when their medication doesn't work well, and have trouble thinking. This study looks at whether partnered dance-aerobic exercise (PDAE), a fun type of exercise, can help with these problems. PDAE involves dancing with a partner, which makes you think about steps and patterns, and keeps your brain active. Previous research showed that PDAE reduced OFF-time and improved thinking abilities. This study will compare PDAE with walking, to see which is better at helping people with PD.

• The study lasts 16 months, with classes twice a week for 3 months, then once a week for 13 months.
• Participants will undergo brain scans to see if PDAE or walking protects brain cells.
• Participants should attend appointments before, during, and after the study for tests and brain scans.

To join, you must be over 40, able to walk, have a certain score on a cognitive test, and be willing to try either exercise. You cannot join if you have conditions like untreated depression, certain heart problems, or have done similar exercises before.