The amygdala regions of interest were derived from the AAL atlas using the WFU PickAtlas Tool, version 1.04 (Wake Forest University School of Medicine, Winston-Salem, NC, USA). Amygdala habituation to threat-related stimuli was calculated as the linear decrease over successive face matching blocks (that is, block 1 > block 2 > block 3> block 4). Individual BOLD values from the functional amygdala clusters exhibiting habituation were extracted using the VOI tool in SPM2. Analyses involving FAAH genotype were conducted using these extracted values outside of SPM2, thereby eliminating any possibility of correlations that are artificially inflated because of extraction and correlation techniques that capitalize on the same data twice.42 In sum, our analytic method was quite conservative and yet still demonstrated robust effects as a function of genotype.
