In the Collaborative Study on the Genetics of Alcoholism (COGA), we have successfully used EROs as endophenotypes in the search for genes involved in alcoholism and related disorders (for reviews, see Porjesz et al., 2005; Pandey et al., 2012; Rangaswamy and Porjesz, 2014). Genetic studies of the theta ERO phenotype in a visual oddball task has been associated with several genes, including CHRM2 (Jones et al., 2004; Jones et al., 2006a), GRM8 (Chen et al., 2009), and HTR7 (Zlojutro et al., 2011). Recently, in the first family-based GWAS of the frontal theta ERO phenotype, Kang et al. (2012) found genome-wide significant association between the frontal theta ERO power to targets in a visual oddball task and several SNPs (including a synonymous SNP, rs702859) in KCNJ6 (KIR3.2/GIRK2, an inward rectifier potassium channel). GIRK2, the protein encoded by KCNJ6, is widely distributed in the brain and is an important functional element in dopaminergic, cholinergic, GABAergic and glutamatergic synapses, and hence the regulation of neuronal excitability (Saenz del Burgo et al., 2008). The advantage of a family-based study design is robustness against population
