**Saliva and Extracellular Vesicles for Neurodegenerative Diseases Study** This study is exploring a new way to find and monitor brain diseases like Alzheimer's and Parkinson's. Researchers want to see if they can use **saliva** (spit) to help diagnose these diseases early. They will also look at tiny parts in the saliva called **Extracellular Vesicles (EVs)** which carry important information about what's happening in the brain. One method they will use is **Raman Spectroscopy (RS)**, a tool that can examine saliva quickly and give a “fingerprint” of what's happening inside it. By studying this fingerprint, doctors might find it easier to diagnose brain diseases, understand how they progress, and create better treatments. **Key Points:** - **Duration & Visits:** The study will last 12 months, with saliva samples collected at the start and after a year. - **Eligibility:** Participants should not have oral or other specific chronic diseases. - **Benefits:** Participation could lead to better understanding and treatment of brain diseases, possibly improving life quality for those affected. The study could help doctors find and treat these diseases earlier, which could make a big difference for patients and their families.