heterozygosities were computed in PLINK (Purcell et al., 2007) using data on founders only included in the larger group. Ethnic stratification was assessed with SNPrelate (Zheng et al., 2012) using 64 ancestry-informative SNPs, as part of a larger 96 SNP panel developed at the Rutgers University DNA and Cell Repository (RUID™). Further details on the genotyping data is available elsewhere (Olfson et al., 2014). The KCNJ6 SNP assayed and used in this study, rs702859, is a synonymous SNP in exon 4 found to be associated with theta EROs to target stimuli in a visual oddball task in our previous GWAS at a genome-wide level of significance (Kang et al., 2012). This SNP had the nucleotides ‘A’ (adenine) as the major allele and ‘G’ (guanine) as the minor allele, and the participants were classified into one of three genotype groups based on the number of minor allele(s): 0 (AA), 1 (AG/GA), and 2 (GG).
