⁃ Age between 18 and 85 years old (aimed to be evenly spread over age intervals).

⁃ Subject is judged to be in good health by the investigator on the basis of medical history, physical examination including vital signs, clinical laboratory test and urinalysis.

⁃ No history or evidence of current major neurological, internal or psychiatric disorder, based on the medical assessment and neuropsychological assessment.

⁃ In subjects \< 60 years of age, an unremarkable structural MRI scan as assessed by expert radiologist. In subjects \>= 60 years of age white matter hyperintensities corresponding to a white matter lesion (WML) score \<= 2 (of 3) on the Age-Related White Matter changes scale are acceptable.

⁃ When older than 50 years of age, subject is willing to undergo an additional 18F-NAV-4694 scan when cerebral amyloid status is unknown.

• Patients referred with uncertain diagnosis and subsequent need for FDG PET brain in their work- up to differentiate between dementing disorders or to exclude dementia in late-onset psychiatric disorders with cognitive impairment.

• A routine neuropsychological assessment has been performed during clinical work-up in the memory clinic.

• Subject is at least 30 years old.