In another neurophysiology example, the amplitude of the event-related potential P3 wave, which indexes orientation toward novel events and inhibition of ongoing cognitive processing, is reduced in individuals with AUD (and externalizing disorders more generally) and in individuals at familial risk for AUD [29–33], especially in male offspring [34]. Linkage analyses of the frontal theta and parietal-occipital delta event-related oscillations (EROs) underlying the P3 component found a linkage peak over the muscarinic acetylcholine receptor M2 (CHRM2) on chromosome 4 [35]. Subsequent association analyses in the COGA sample found significant association among variants in the glutamate receptor, metabotropic 8 (GRM8) gene and theta EROs [36]; variants in the corticotropin releasing hormone receptor 1 gene (CRHR1) on chromosome 17 and P3 amplitude [37]; and variants in KCNJ6 on chromosome 21 and frontal theta oscillations [38]. Variation in CHRM2, GRM8, CRHR1, and KCNJ6 has also been associated with alcohol and/or drug dependence [39, 40, 37, 36].
