Alterations in rsFC strength between ventral striatum and various subcortical and cortical regions have been observed when comparing cocaine (Tomasi et al., 2010; Gu et al., 2010; Wilcox et al., 2011), prescription opioid (Upadhyay et al., 2010), and heroin dependent individuals (Ma, 2010) with matched, non-drug using controls. Although altered MCL circuitry has been consistently observed in drug addicts, synthesis of a cogent narrative surrounding the precise circuits and direction of change is difficult from these initial studies. While, on the one hand, some studies have reported increased rsFC between MCL regions and subcortical and cortical areas (Ma 2010; Wilcox 2011), others have reported decreased connectivity (Upadhyay 2010, Gu 2010, Tomasi 2010, Wang 2010). For example, testing the hypothesis that MCL circuits are altered in heroin addicts, Ma and colleagues (2010) noted stronger rsFC between NAc and the ventral aspects of medial prefrontal cortex including rostral ACC and medial OFC). Although using a small (n=14) and a heterogeneous subject group (i.e., both methadone maintained and abstinent users), these results suggest enhanced connectivity within reward and motivation circuits that may be
