NCs. Besides, the alterations mainly concentrated on the anteriorand posterior regions associated with the default mode network(DMN) (36). See Figure 2.Glucose is an important energy source for brain function.Abnormal glucose uptake in different regions may be relatedto the extent of altered brain function. 18F-fluorodeoxyglucoseposition emission tomography (FDG-PET) can reflect changesin glucose metabolism in different parts of the brain (57).Scheef et al. (57) reported that, compared to the controlgroup, metabolic rates in right precuneus and left parietalcortex are lower in SCD patients, while metabolic rates inmedial temporal lobe and right para-hippocampal gyrus arehigher, suggesting simultaneous abnormal energy metabolismand neuronal dysfunction in certain regions of SCD patients. Andthe decline in executive ability of SCD patients was associatedwith Aβ deposition in a Pittsburgh Compound B PET (PIB-PET)study (58). In recent years, breakthroughs in SCD research havebeen achieved by applying Flobetapir F-18 to Florbetapir-PET(amyloid-PET) techniques with improved sensitivity. FlobetapirF-18 has a higher affinity for Aβ accumulated in the brain and the