This study looks at people with a condition called **REM sleep behavior disorder (RBD)**, where they act out dreams, and compares them with healthy people. RBD can sometimes lead to diseases like Parkinson's. The goal is to prepare for a trial to find treatments to protect the brain from these diseases, known as **synucleinopathies**. Participants will undergo tests like questionnaires, blood draws, and scans. RBD participants will also have two overnight sleep studies. The study gathers important data to create a list of participants ready for future trials and to find markers that indicate the diseases before symptoms appear.

• The study involves multiple tests, including sleep studies for those with RBD.
• Participants must be over 18, able to consent, and meet specific health criteria.
• Some procedures, like lumbar punctures, are optional for RBD participants but required for controls.