during a masked affective paradigm is perhaps not unexpected. The relationship between both amount of use and overall cannabinoid concentration level and the BOLD signal changes suggest an effect of marijuana use in these regions which may impact the ability for individuals who are chronic, heavy marijuana smokers to process affective stimuli, even if not consciously doing so. This finding may explain why, as a group, the chronic, heavy marijuana smoking group demonstrates altered patterns of activation in these regions, as the amount of marijuana smoked per week may affect cingulate and amygdalar activity, evident during these two tasks. Further, in addition to lower overall activation in the marijuana smokers relative to the control subjects in the anterior cingulate, the activation detected for the marijuana smokers was more posteriorly located, perhaps reflective of a compensatory action of this region. In previous studies of cingulate function in marijuana smokers, findings have suggested that these individuals utilize different cortical processes from control subjects in order to complete tasks (Eldreth et al., 2004; Gruber and Yurgelun-Todd, 2005), which may represent an inherent alteration of the cingulate itself.
