Alcoholism is part of a spectrum of disinhibitory disorders, which include externalizing and substance use disorders; a shared set of genetic factors influencing impulse control are postulated to underlie these co-occurring disinhibitory disorders (Kendler et al. 2003; Lahey et al. 2011). Hence, examining neuroelectric phenotypes that reflect shared liabilities provides a powerful strategy to investigate underlying risk for alcoholism and related disorders (Porjesz & Rangaswamy 2007; Rangaswamy & Porjesz 2008). Our earlier studies have shown that both delta and theta power are significantly reduced in alcoholics and adolescent offspring of alcoholics when compared with normal controls during target processing in a visual oddball paradigm (Jones et al. 2006b; Rangaswamy et al. 2007). Frontal theta ERO has successfully served as an endophenotype in family and case-control genetic studies in the Collaborative Study on the Genetics of Alcoholism (COGA) (Chen et al. 2009;Jones et al. 2006a; Jones et al. 2004; Zlojutro et al. 2011). This study examines the theta ERO endophenotype recorded at the midline frontal (Fz) electrode in response to targets in a visual oddball paradigm in a family-based genome-wide association
