Addiction to drugs and alcohol involves a cascade of neuroadaptive processes, causing changes in the brain circuitries at different stages of addiction [18,89,90]. Our findings on resting state FC in the reward network indicate that AUD subjects manifested alterations in connectivity patterns, in terms of hypoconnectivity in nine connections and hyperconnectivity in three connections, involving 17 key reward structures [see Figure 7]. In particular, out of the nine reward network functional connections that showed hypoconnectivity, three were cortico–cortical connections (R.Ins–R.ACC, R.ACC–R.OFC, and R.ACC–R.PCC) in the right hemisphere, and five were subcortical–subcortical connections (R.Amg–L.Hip, L.Cdt–R.Pal, L.Tha–R.Tha, L.Cdt–L.Tha, and L.Tha–R.Ptm) involving both hemispheres, and a single inter-hemispheric subcortical-cortical connection (R.VTA–L.ACC). The three subnetworks that were hyperconnected in AUD individuals were subcortical–cortical connections, involving a left-hemispheric connection (L.NAc–L.PCC), a right-hemispheric connection (R.Pal–R.PCC), and an inter-hemispheric connection (R.Hip–L.DLP). These findings of altered brain connectivity in AUD individuals may be suggestive of neuroadaptation in the hub regions of the reward network, caused by chronic alcohol intake. In general, previous fMRI studies have reported such aberrations in resting state connectivity underlying multiple brain networks in individuals
