A total of six functional imaging scans of combined olfactory/visual stimulation were performed (24 2-second odor events in each of the 3 stimulus classes of AcO, AppCo, and SO were intermixed with 32 2-second IAPS image presentations), with two scans completed for each mood (2 positive image scans, 2 negative image scans, and 2 neutral image scans). Scan order was randomly assigned, with a break after the first three scans, although randomization was restricted so that all three moods were experienced prior to and again following the break (see Figure 1). Participants reported the presence (left click) or absence (right click) of an odorant on an MRI-compatible trackball (Current Designs, Philadelphia, PA) while exhaling, but were not asked to identify the odorants. Between scans, participants again rated their current mood using the Affect Grid, and their current craving for any drink, grape juice, and alcohol.
