To determine fronto-striatal functional connectivity during alcohol cue presentation, separate whole-brain PPI analyses from the Alcohol versus Water contrast describing strength of connectivity between the right ventral striatum (including the accumbens) and the rest of the brain and the right primarily dorsal striatum (caudate) and the rest of the brain were performed. These analyses carefully followed published procedures for PPI implementation and interpretation (O'Reilly et al., 2012). No regions of significant positive activation clusters were found across all subjects for either seed region in the PPI analysis; however, the negative PPI results revealed weaker correlations (decreased functional connectivity) between striatal seed regions and mostly posterior brain regions during the presentation of the alcohol- versus water-cues (see Table 5, Figures 5 and 6). Furthermore, functional connectivity with each seed region was found to differ between OPRM1 genotypes in the G-allele carriers versus A-allele homozygotes contrast (parameter estimates for the cluster: G carriers = −0.271, A homozygotes = 0.012; for PPI activation maps for each genotype group see supplementary materials). Specifically, G-allele carriers exhibited stronger negative correlations between the right ventral striatum
