Mean FRN amplitudes for positive and negative feedback for the three electrode sites (Fz, FCz, and Cz) are presented in Table 2. The grand averages for the two types of feedback at each electrode site are depicted in Fig. 3 and the topographical distribution of the current source density (CSD) of the FRN for each group and condition is displayed in Fig. 4. Repeated measures ANOVA conducted on peak FRN amplitude revealed a significant main effect of feedback valence [F (1, 59) = 4.89, p < 0.05]. Post hoc test revealed that the FRN was larger for negative feedback indicating loss (−3.2 μV) as compared to positive feedback indicating gain (−1.9 μV). There was no significant main effect of electrode site [F (2, 58) = 0.01, p = 0.99]. Importantly, neither the main effect of group [F (1, 59) = 0.07, p = 0.80] nor the interaction effect of group and feedback valence [F (1, 59) = 2.07, p = 0.16] did reach statistical significance. Table 2Mean and SD of FRN amplitude for the alcohol (n = 31) and placebo group (n = 30)FeedbackAlcohol groupPlacebo groupMeanSDMeanSDPositive Fz−2.252.45−1.743.81 FCz−2.203.18−1.576.14 Cz−2.222.94−1.574.20Negative Fz−2.863.49−3.334.20 FCz−2.434.20−3.995.78 Cz−2.673.73−3.655.03
