Two hypotheses concerning fronto-striatal functional connectivity were considered based on alternative explanations for greater reward-driven behavior in G-allele carriers versus A-allele homozygote groups. First, we hypothesized weaker connectivity in the G-allele carriers suggesting disregulation of ventral striatal reward signals by frontal regions; however, this was not confirmed as we found stronger connectivity between the two regions. Our alternative hypothesis was consistent with this finding as it assumed that fronto-striatal connectivity reflects greater demand for frontal regulation over subcortical signals reflecting heightened reward sensitivity (Heatherton and Wagner, 2011). The negative direction of functional connectivity (negative correlation between signals across regions) suggests the possibility that G-allele carriers require greater frontal recruitment for self-regulation. Given studies indicating self-control as a limited resource (Baumeister et al., 1998; Hagger et al., 2010), the negative connectivity observed in this study may reflect a cycle of increased frontal control of reward-related striatal signals (i.e., increased frontal and decreased striatal activation) followed by depletion of frontal control processes resulting in unregulated reward signals (i.e., decreased frontal and decreased striatal activation). Such unstable control processes may underlie the differences
