Hypothetical model of preclinical Alzheimer's disease (AD). According to the proposed model, the group currently defined as 'preclinical AD' is heterogeneous and comprises two subpopulations. Firstly, there is the group of individuals at different stages of preclinical AD defined by the biomarkers indicated in the lower panel of the figure. All of these individuals will progress to dementia, and we call this phase 'presymptomatic AD'. The second group comprises individuals who are positive for amyloid markers and neuronal injury markers, and fall into one of the stages of preclinical AD, based on the current classification. However, this population has efficient active compensatory mechanisms, and remains resistant to dementia (stable asymptomatic cerebral amyloidosis).