Our results indicate reduced network characteristics in terms of local efficiency, global efficiency, clustering coefficients, and node betweenness centrality in a resting state. In line with our work, a recent study found decreased local and global efficiency and clustering coefficients in middle-aged subjects compared to young adults [6]. In the previous study, a decrease in clustering coefficients confirmed age-related differences in oscillatory networks in young adults and elderly individuals, thus reinforcing our findings [18]. An increased path length indicates a less organized network characterized by less power in older adults, which confirms our results for the eyes-closed state [11]. With the eyes open, functional connectivity was decreased in alpha and beta frequency bands [58,59]. The opening or closing of the eyes can result in the functional connectivity of the brain being turned into an interoceptive or exteroceptive state [60]. Evidently, eyes-open and eyes-closed states have an impact on brain functional connectivity and network communication, implying that aging can generate more random brain networks in line with eyes-open and eyes-closed states [18,61,62]. Furthermore, our results confirm age-related differences between middle-aged and elderly individuals in terms of oscillatory networks
