RecruitingDiagnostic testA Study of Neurodegeneration and Neuronal Fluctuations in Lewy Body Disease and Alzheimer's DiseaseThe purpose of this research study is to investigate how the brain, memory, thinking, and motor behavior change both in individuals with movement and/or cognitive disorders, as well as healthy individuals. Researchers will look at measurements of memory, thinking, brain wave and muscle activity, daily functioning, and brain scans to learn more about brain disorders such as Alzheimer disease and Lewy body disease.