## 4 Discussion
The global connectivity analysis gave an overview of the AD process in the brain. Although it resulted in identifying higher connectivity that was distributed in the brains of the AD group, it could not localize the effect. Indeed, the effect of [PERSON]'s disease tends to be more prominent in some areas of the brain than others [30; 31], hence justifying a motive to pursue a further analysis with the homotopic pair connectivity. Similar to the band division performed to retrieve the PSD in a spectral analysis, in functional connectivity studies involving AD subjects, electrode pairs can be singled out and evaluated separately, instead of combining them all together [36]. The analysis of homotopic pairs revealed a significant difference of connectivity in the delta band of the pairs in the fronto-central and the parieto-occipital regions, whereas these effects were diminished in the global connectivity analysis, which only found a significant difference between the groups in the theta band. The result indicating a higher functional connectivity of the AD brains conflicts with the study of [PERSON] et al. [12], who reported a lower lagged phase synchronization in the delta and theta bands of AD patients. Indeed, a decreased connectivity between brain regions can be expected, as AD is known to cause neuronal loss and the damage of neural pathways [1; 22; 8]. However, other studies suggest that the impact of such damage is only reflected in fast signals, as healthy participants have a higher brain connectivity in alpha and beta bands [19; 20] but not in the lower frequency bands. On the other hand, it has been shown in the past that patients suffering from neuropsychiatric disorders such as schizophrenia and epilepsy display an increased functional activity between brain networks as a sign of anomaly in information communication [37; 38]. In the study of [PERSON] et al. [17], similar patterns were reported for AD patients, where the connectivity within the same frequency band (intra-band connectivity) was stronger in AD brains than in the healthy brain, whereas the connectivity between the frequency bands (inter-band connectivity) was significantly weaker. Observing higher synchronization values in the lower frequency bands for AD subjects can therefore be interpreted as a sign of brain dysfunction [17; 20]. More specifically, this study demonstrated that the brains affected by [PERSON]'s disease seemed to be in a 'phase-lock' state, causing a high connectivity in the low frequency bands; this is an observation that is well in line with the existing literature [6; 17; 19; 30; 36]. The localization of AD analysis reached the conclusion that there was a significant difference in the connectivity between the AD and HC groups in the theta band for two out of four homotopic pairs. The answer to the secondary research question (RQ2) is therefore positive; it is possible to localize to some extent the differences between a healthy brain and one suffering from AD-induced dementia. The findings of this study therefore provide further evidence for damaged neural connections and, consequently, abnormal network dynamics in AD-affected brains, particularly in the centro-parietal and centro-temporal regions. While older studies such as [39] suggested that the effects of AD are not situated in one specific area of the brain, the regions identified by this study are in line with the report of more recent studies such as [PERSON] et al. [40] which observed a significant decrease in signal complexity of the AD group in the occipito-parietal and temporal regions of the brain using'multivariate multi-scale weighted permutation entropy' (MMSWPE) [40]. It is important to note that the findings of this study do not suggest that other brain regions should be excluded in future comparisons between the AD and HC groups. In fact, several studies have indicated that patients suffering from AD tend to have a disruption in brain connectivity in various areas of the brain, as well as in various stages of the disease [41].