Only a few studies have investigated the changes in CFC in patients with AD. Here, two of the studies have found decreased CFC (Poza et al., 2017; Goodman et al., 2018), while one study found increased CFC (Wang et al., 2017) in patients with AD compared to HC using the amplitude at a high-frequency band and the phase at a low-frequency band. In the current study, we found, although not significant, that gamma/theta CFC was decreased in both patients with AD and MCI compared to that in HC. This finding suggests that patients with AD show a disruption of the coupling between the frequency bands. More interestingly, we found that gamma/theta CFC was decreased in pMCI compared to sMCI. Gamma/theta CFC has been associated with activity in the hippocampus and performance in memory tasks in rodents (Tort et al., 2009; Canolty and Knight, 2010; Lisman and Jensen, 2013) and has been shown to be vital for working memory in humans (Axmacher et al., 2010). This could suggest a disruption of brain areas known to be affected in AD. We hypothesize
