Here are some places where you can look for information about OASIS-3: Longitudinal Multimodal Neuroimaging, Clinical, and Cognitive Dataset for Normal Aging and Alzheimer’s Disease:

Homepage
OASIS-3: Longitudinal Multimodal Neuroimaging, Clinical, and Cognitive Dataset for Normal Aging and Alzheimer’s Disease has a homepage that can be found at https://sites.wustl.edu/oasisbrains/home/oasis-3/