Brain scans across conditions
Compare the most replicated structural and functional imaging findings, with evidence strength and limitations kept visible.
These are averages across research groups with substantial overlap. Imaging must be interpreted with symptoms, history and clinical examination; psychiatric and personality effect sizes are usually small.
Alzheimer's disease
Evidence: StrongThe best-established pattern combines medial-temporal neurodegeneration with amyloid/tau pathology and reduced posterior metabolism.
Primary modality: MRI plus amyloid/tau PET or FDG-PET
Imaging may support clinical diagnosisStructural findings
- Hippocampal and entorhinal volume is lower than in matched controls
- Medial-temporal cortex thins early
Functional findings
- Posterior cingulate/precuneus metabolism is reduced
- Amyloid and tau tracers show characteristic protein deposition
Convergent biomarkers are incorporated into modern NIA-AA biological criteria.
These are averages across groups, with substantial overlap with people who do not have the condition. A brain scan alone cannot diagnose it; imaging only supports a diagnosis made in full clinical context. Age, medication, comorbidity, substance use and head motion can confound studies.