Subsequently, participants took part in both placebo and alcohol sessions that were 17 ± 13 days apart on average, in a counterbalanced order, so that alcohol was presented in the first session for half the sample and in the second session for the other half. The within-subject design minimized influence of individual differences in neuroanatomy and alcohol metabolism yielding reduced error variance and increased statistical power. Subjects were asked to abstain from food for 3 h and from alcohol for at least 48 h prior to each experimental session. To confirm that they were not pregnant, women were given a urine test prior to each scanning session. Breath alcohol concentration (BrAC) was measured with a breathalyzer (Draeger, Inc.) upon arrival and throughout the session, except when subjects were inside the recording chamber. Subjects rated their moods and feelings with the Biphasic Alcohol Effects Scale (BAES, Martin et al., 1993) prior to drinking (at baseline), immediately before and after the task. In the alcohol session, the beverage contained 0.60 g/kg of ethanol for men and 0.55 g/kg for women and was
