Although our primary hypotheses involved these medial frontal regions (in which the prior analysis of family history pointed to evidence of a genetic effect), we also examined other regions post-hoc, including the VTA, ventral striatum, and caudate heads, using ROIs as described in Kareken et al. (2010). The MarsBar utility (Brett, et al, 2002; http://marsbar.sourceforge.net/) was used to extract each subject's mean AO and ApCO contrast value (i.e., the output of the subject-specific fixed effect model, each relative to odorless sniffing) by averaging across all voxels within each of the above ROIs. These average contrast values were then analyzed in the linear mixed-effects models described above.
