A monetary gambling task was implemented as detailed elsewhere 47. Briefly, individuals bet 50¢ or 10¢ in each of 172 trials, with one of four possible outcomes: lose 50¢, lose 10¢, gain 50¢, or gain 10¢, with equal number of loss and gain trials (Supplemental Figure 1). Evoked theta ERO power (3.5–7.5 Hz) during monetary loss and gain feedback were measured and differential reward processing (‘loss – gain’) was derived at frontal, central, and parietal regions (Supplemental Figure 2). Linear regression was applied to test the associations between the top variants and theta ERO power after adjusting for sex, age, and first three PCs. We did not examine rs1229984 in ADH1B in either the COGA Prospective Sample or the Duke Neurogenetics Study (below) due to its well-known role in the alcohol metabolizing process. For the remaining four GWS loci (rs61826952 and rs7597960 from EA+AA meta-analysis, as well as rs188227250 and rs1912461 from the EA GWAS), three brain regions were tested; therefore, after multiple testing correction, the significance threshold was p≤0.0042 (i.e., 12 tests). Further details on data acquisition and processing are in Supplemental Text.
