The aim of the study is to investigate and compare the relationship between the action of amisulpride at brain sites during the first 10 weeks of amisulpride treatment in two patient groups - Alzheimer's disease and schizophrenia-like illness. Imaging data will be combined with data on drug dosage, levels of drug in the bloodstream and clinical response (symptom reduction and motor side effects) during dose titration.Dose-response modelling will be carried out in both groups to establish the minimum clinically effective dose of amisulpride, optimum dose range and impact of variability and covariates on exposure-response relationships