Our connectivity analyses revealed the presence of both decreases and increases in lagged phase synchronization, as a measure of functional connectivity, affecting alpha and theta frequency band, respectively. Consistent with our findings of decreased alpha2 connectivity in left temporal and medial/lateral parietal regions, previous neurophysiological studies using coherence or synchronization likelihood noted that synchronized activity, particularly in the alpha band, disintegrates in AD and other types of degenerative dementia, indicating disruption in neuronal comunication [12], [17], [19], [38], [39]. Furthermore, fMRI age-related connectivity loss is often found in the temporal lobe as well as in posterior areas of the DMN, including the posterior cingulate, medial parietal (i.e., precuneus) and inferior parietal cortex, which are selectively vulnerable to early amyloid deposition or show decreased metabolism early in the course of AD [14], [37], [69], [70].
