Amidst the predominant profile of hyperconnectivity in AUD, 4 of the 29 connections across prefrontal regions (PFC and ACC) and posterior right-hemispheric regions (IPL, LTC, and PHG) showed hypoconnectivity in delta and beta band (Figure 5, panels a & d). The strongest hypoconnectivity (p ≤ 0.001) was observed between left and right PFC in the delta band (Figure 6). Delta rhythm consists of slow oscillations that are involved in the dynamic coordination of large-scale cortical networks and modulation of faster rhythms through cross-frequency coupling [134]. Therefore, it is possible that hypoconnectivity of these prefrontal nodes with other DMN regions observed in both slow (delta) and fast (beta) oscillations in AUD individuals may have been primarily caused by the dominant delta rhythm which may have also modulated the connectivity in beta oscillations via cross-frequency coupling. On the other hand, since the connectivity across these regions were relatively weaker in AUD (i.e., hypoconnectivity) than controls, these results may suggest a weaker or fractured connectivity of the prefrontal nodes with other cortical regions. It is well-established that the prefrontal cortex, which is highly
