To better understand the nature of the activation, we extracted average BOLD contrast values (without applying a threshold) from each a priori medial frontal ROI (left and right mPFC, vmPFC) and tested in a Mood (3) × Odor (AcO vs. AppCo) linear mixed-effects model. The Left vmPFC ROI showed a significant effect of Odor (p < 0.001), and an interaction between odor and mood that fell short of significance (p = 0.08), in which [AcO > AppCo] contrast activation was greatest under negative mood (see Figure 4); contrary to our hypothesis, there was no main effect of Mood (p = 0.51). The left mPFC and right vmPFC ROIs had significant odor effects only (p = 0.002 and p = 0.01, respectively). There were no significant effects in the right mPFC ROI.
