Additionally, other multi-modal imaging techniques such as fMRI with MR spectroscopy or flumazenil-PET may also offer interesting insight into AD pathology and FC [for reviews, see Ref (53–55)] but, unlike FDG-PET/fMRI, they do not yet offer the key aspect of directionality of functional pathways, along which animal models have shown amyloid-β and tau pathology to spread (7). Here, MAPT is linked to Alzheimer disease.