The dementia in AD is caused by severe atrophy of the cerebral cortex, as indicated by the widening of the sulci and narrowing of the gyri (Figure 3) while normal aged individuals have broad gyri and narrow sulci (Figure 3). Neurons in the neocortex, hippocampus, basal forebrain, and brainstem (e.g., dorsal raphe) are selectively vulnerable in AD [239,240,241,242,243]. The numerous lesions that are formed in the brains of AD patients are called senile plaques, containing abnormal extracellular deposits of Aβ amyloid protein (Figure 3, arrows), and NFTs which are abnormal intracellular aggregates of protein containing hyperphosphorylated tau (Figure 3, arrows).