Figure 1. Neuropathological hallmarks that characterize Alzheimer’s disease. As Alzheimer's disease progresses, the brain tissue shrinks, the volume of the ventricle, which contains cerebrospinal fluid, increases markedly. At the molecular level: 1. Amyloid-β peptides are produced by the cleavage of the amyloid precursor protein (APP) in the membrane of the neurons. 2. In the space between the neurons, amyloid-β forms oligomers that are thought to disrupt the function of the synapses and act in receptors present in the neuron plasma membrane. 3. The fibrils of the amyloid-β oligomers are added in plaques, which interfere with the function of the neurons. 4. Tau hyperphosphorylation causes neurofibrillary tangles within neurons, displacing intracellular organelles and disrupting vesicular transport.