cingulate activity during the viewing of masked happy faces, in approximately the same region as demonstrated for the chronic, heavy marijuana smokers compared to the non-marijuana smoking controls during the viewing of masked happy faces. The positive associations between marijuana use and BOLD activation within both cingulate and amygdalar regions depending on the stimuli may represent an alteration of fronto-limbic circuitry response within the marijuana smoking subjects. Given the relative activation differences between the marijuana smokers and non-smoking control subjects, it would appear that within the marijuana smoking group, increased marijuana use tends to normalize cingulate response to masked angry stimuli while it enhances the positive response to masked happy stimuli. This interpretation is consistent with previous self-reports of marijuana smokers feeling “mellow” and happy when smoking marijuana.
