EROs have proved to be more useful than ERPs in the search for genes involved in AUDs and related disorders in COGA. Theta oscillations to targets have been instrumental in identifying two excellent candidate genes under a significant linkage peak – CHRM2 and GRM8. Both encode subunits of neurotransmitter receptors: CHRM2 encodes a cholinergic muscarinic receptor M2, whereas GRM8 encodes the metabotropic glutamate receptor 8 in a family of G-protein-coupled receptors. Significant associations were observed between the frontal theta ERO and SNPs in CHRM2, and to parietal delta (Jones et al., 2004, 2006a). Several of the same SNPs were significantly associated with alcohol dependence along with depression, drug dependence and externalizing disorders (DSM-IV) (Wang et al., 2004; Dick et al., 2007), findings that were replicated by other groups (Comings et al., 2002; Luo et al., 2005). Theta oscillations were also significantly associated with several SNPs in GRM8, as well as alcohol dependence (Chen et al., 2008a).
