We performed mediation analyses to test the hypothesis that regional activations mediate the association between the AUDIT score and SSRT, using the toolbox M3 developed by Wager and Lindquist (http://www.columbia.edu/cu/psychology/tor/). The methods were detailed in our previous work (Ide and Li, 2011). Briefly, in a mediation analysis, the relation between the independent variable X and dependent variable Y, i.e., X → Y, is tested to see if it is significantly mediated by a variable M. The mediation test is performed by employing three regression equations: Y=i1+cX+e1Y=i2+c′X+bM+e2M=i3+aX+e3 where a represents X → M, b represents M → Y (controlling for X), c′ represents X → Y (controlling for M), and c represents X → Y. In the literature, a, b, c, and c′ were referred as path coefficients or simply paths, and we followed this notation. Variable M is said to be a mediator of connection X → Y, if (c – c′) is significantly different from 0, which is mathematically equivalent to the product of the paths a× b (MacKinnon et al., 2007). If the product of a× b and
