This paper presents the first genome-wide association study of an ERO phenotype – frontal theta oscillations (Fz electrode) to visual targets in a visual oddball paradigm during the P300 response time window. Theta EROs have been related to fronto-limbic interactions associated with a complex set of cognitive functions, including conscious awareness, attention, memory-related processes, and frontal inhibitory control, and has exhibited marked energy reductions in alcoholics and their offspring [Jones et al., 2006b; Rangaswamy et al., 2007]. Significant linkage and association has been previously reported for CHRM2 and GRM8 polymorphisms for the theta ERO endophenotype and diagnoses (DSM-IV and ICD-10) of alcohol dependence [Jones et al., 2004, 2006a; Chen et al., 2009], implicating both the cholinergic and glutamatergic neurotransmitter systems. None of the top GWAS hits in the present study come from these two genes, but some promising signals are observed, including rs1362178 (P = 0.0034) from GRM8 and rs17168817 (P = 0.033) from CHRM2. None of the most associated markers (P < 0.01; N = 10) identified in these earlier studies were captured by the Illumina HumanHap 1M microarray
