Three functional imaging scans of olfactory stimulation per subject-session were performed (24 odor events in each of the three stimulus classes of AO, ApCO and NApO plus 42 odorless control events; see online supplementary figure). No pictures were presented during imaging, and olfactory stimulation was done with the eyes closed. Subjects reported the presence (button 1) or absence (button 2) of an odorant on an MRI-compatible response box (Current Designs, Inc., Philadelphia, PA), but were not asked to identify the odorants.
