Very few studies have examined electrophysiology and genetics in humans. Small effects from several genes associated with neurotransmitters may contribute to the variation in P300 and theta and delta oscillations during cognitive tasks. The neurochemical basis of the target stimulus response and P300 component has been suggested to be triggered by glutamatergic activity and modulated by influences from both cholinergic and GABAergic sources (Frodl-Bauch et al. 1999; Kenemans & Kahkonen 2011). Previous studies conducted in COGA examining the genetics of EROs have employed whole genome linkage followed by candidate gene association methods on family and case control data. Based on the regions identified in whole genome linkage scans with theta EROs, we identified candidate genes, namely, GRM8 (metabotropic glutamate receptor) and CHRM2 (muscarinic cholinergic receptor), and subsequently reported that SNPs in both candidate genes are associated with theta EROs to targets (Chen et al. 2009; Jones et al. 2006a; Jones et al. 2004). In this study, we also found several SNPs in both CHRM2 and GRM8 genes were significantly associated with frontal theta EROs; however, not quite at the level
