In order to address this issue, we acquired BOLD fMRI data from both chronic heavy marijuana smokers and non-marijuana smoking control subjects while undergoing a masked facial affect paradigm to examine whether chronic, heavy marijuana smokers would demonstrate a different pattern of activation during the completion of this task. One clear advantage of using a masked paradigm is that since stimuli are presented very rapidly, in fact, below the level of conscious awareness, it avoids confounding interpretation by the presence of other cognitive processes during the scan. We hypothesized that given the increased behavioral impulsivity often noted in chronic marijuana smokers and previous findings of altered anterior cingulate activation, chronic heavy marijuana smokers would likely demonstrate different frontal patterns of activity relative to non-marijuana smoking control subjects in response to affective stimuli, even if presented below the level of conscious processing. We also predicted differential amygdalar response to the masked affective stimuli, given the CB1 receptors located within the amygdala-prefrontal circuit (Laviolette and Grace, 2006), which have been shown to modulate emotional associative learning. Given previous fMRI findings of altered
