3. Investigate the heterogeneity of dementia and parkinsonian disorders to assist in the development of a new pathology-based disease classification. Current diagnostic work-up is based on symptomatology. However, the diseases (e.g. Alzheimer's and Parkinson's diseases) are heterogeneous with respect to clinical features and underlying pathologies. Moreover, there is also significant overlap between the diseases. Hence, today's symptom-based clinical diagnostic criteria are likely too crude to provide an etiologically meaningful classification of patients. We will therefore work towards a pathology-based disease classification, using in vivo biomarkers that reflect the underlying brain pathologies, e.g. Aβ or tau. This will be especially useful for the development of new disease-modifying therapies, which are aimed at specific brain pathologies.