In the first study, we used imaging genetics in a sample of middle-aged adults (N = 81) who performed a ‘threatening faces’ task that elicits robust amygdala reactivity on initial face-viewing, and subsequent amygdala habituation with repeated viewing.46 All subjects showed significant amygdala habituation to threatening faces, calculated as a linear decrease over successive viewing, in the right hemisphere dorsally (x = 24, y = −8, z = −11, z = 4.58, t-test: t(79) = 4.92, P<0.01) and ventrally (x = 32, y = −1, z = −20, z = 4.36, t-test: t(79) = 4.64, P<0.01), and left hemisphere (x = −26, y = −1, z = −13, z = 3.89, t-test: t(79) = 4.10, P<0.01). However, the rate of habituation differed significantly as a function of FAAH genotype (Figures 4a and b), with individuals carrying the lesser-expressing 385A variant demonstrating significantly greater habituation compared with C385 homozygotes in all three clusters (right dorsal: t-test: t(79) = 2.15, P<0.05; right ventral: t(79) = 3.15, P<0.01; left: t-test: t(79) = 2.26, P<0.05). While C385A genotype has previously been associated with human
