Advanced neuroimaging methods towards characterization of early stages of Alzheimer's disease

In the past 5 years, imaging network properties in the brain of patients with Alzheimer's disease (AD) has revolutionized our understanding of this disorder. Postmortem data had already suggested that the damage spreads along functional neural networks, but postmortem studies do not provide information on the temporal evolution of the damage in the same patient, essential to determine spreading. These data can be provided by functional and structural neuroimaging, which allow for the visualization over time of the progressive damage inflicted by AD. Functional networks can be mapped by determining the synchrony across brain regions of the blood oxygenation level dependence (BOLD) signal on functional magnetic resonance imaging (MRI) during quiet wakefulness. Other less extensively used techniques are also useful. For instance, amyloid deposition can be imaged and its progression mapped to determine whether it follows brain networks, and, if so, which are affected earliest. Network patterns of neurobiological changes, including tau deposition, may prove critical to our understanding of the neurobiology of AD and therefore open the way for therapeutic interventions.