Graph theoretical analysis of network organization in AD has shown a loss of small-world structure toward a more ‘random’ network topology,75-78 indicated by a reduction in the clustering coefficient values,75,76,78 and lower characteristic path length.75,77,78 The topography of network abnormalities assessed with this technique is in line with previous studies, showing reduced connectivity in the hippocampus and posterior parietal regions with fMRI,76,77 and in the alpha (8-10Hz) and beta (13-30Hz) frequency bands with MEG.75,78 In addition, Stam et al. have shown greater ‘hub’ vulnerability in AD, as simulated targeted attacks to highly connected nodes better explained the network changes observed in the alpha frequency band than ‘random’ removal of nodes.75 A single study has assessed structural network connectivity, reporting abnormal network topology in AD.79
