Metabolic connectivity in Alzheimer’s diseases

Multiple studies have investigated the disruptions in structural and functional connectivity in aging, dementia and Alzheimer’s disease (AD). The study of metabolic connectivity between brain regions using fluorodeoxyglucose positron emission tomography (FDG-PET) however, is a new focus of interest. Several methodological approaches, including seed-based correlation, independent and principal component analysis, and graph-theoretical approaches have been employed to study the metabolic disconnectivity in AD. We conducted a systematic search of the literature using the keywords metabolic connectivity and Alzheimer disease, up to the date of last submission and included 15 original articles as relevant. Existing literature implies a generalized metabolic disconnectivity in the brain which closely follow findings from functional studies. In the following review, we introduce the concept of metabolic disconnectivity and discuss the alterations in metabolic connectivity in AD and the potential underlying mechanisms. We find it imperative for future studies to investigate alterations in metabolic and functional connectome of AD and mild cognitive disorder through simultaneous acquisition of FDD-PET, functional and structural scans.