Discovery and Validation of Genetic Variants Affecting Microglial Activation in Alzheimer's Disease

This study is looking for genetic factors that influence how immune cells in the brain (called microglia) become activated in Alzheimer's disease. Researchers want to understand why some people are more likely to develop brain inflammation linked to Alzheimer's. The study involves brain imaging and blood or spinal fluid tests — no experimental treatment is given. **You may be eligible if:** - You are 50 years or older - You have been diagnosed with mild cognitive impairment or Alzheimer's disease, OR you have no memory problems (healthy controls are also needed) - You have had a brain scan or spinal fluid test consistent with Alzheimer's changes (or negative, for controls) - You identify as White, non-Hispanic - You speak and read English fluently **You may NOT be eligible if:** - Your memory problems are caused by a condition other than Alzheimer's - You have had cancer in the past 5 years, severe epilepsy, or other serious brain conditions - You are unable to have an MRI or PET scan - You take blood thinners or immunosuppressive medication - You have a chronic inflammatory disease such as MS, lupus, or rheumatoid arthritis Talk to your doctor to see if this trial is right for you.