Impaired long distance functional connectivity and weighted network architecture in Alzheimer's disease

contributions to this work and should be regarded as joint first authors. Alzheimer’s disease (AD) is increasingly recognized as a disconnec-tion syndrome, which leads to cognitive impairment due to the dis-ruption of functional activity across large networks or systems of interconnected brain regions. We explored abnormal functional magnetic resonance imaging (fMRI) resting-state dynamics, func-tional connectivity, and weighted functional networks, in a sample of patients with severe AD (N = 18) and age-matched healthy vol-unteers (N = 21). We found that patients had reduced amplitude and regional homogeneity of low-frequency fMRI oscillations, and reduced the strength of functional connectivity, in several regions previously described as components of the default mode network, for example, medial posterior parietal cortex and dorsal medial pre-frontal cortex. In patients with severe AD, functional connectivity was particularly attenuated between regions that were separate