In parallel with analyses of alcohol dependence, the COGA investigators also examined the evidence of linkage with other alcohol-related phenotypes such as EEG-β. Alcoholics have increased power in the β frequency of the electroencephalogram 53, 54, as do their offspring, who have not been exposed to alcohol 55, 56. Thus, EEG-β is a heritable trait variable rather than simply a marker of excessive alcohol exposure. EEG-β are high frequency oscillations important in short-range neural communication. Of note, the initial linkage peak on chromosome 4p was stronger with EEG-β57, 58. A set of SNPs in GABRA2, which overlapped with SNPs associated with alcohol dependence, was associated with this electrophysiological phenotype43. More recently, SNPs in GABRA2 have been associated with excess EEG fast activity in a sample of alcohol dependent and control individuals from the UK59. SNPs in GABRA2 are also associated with impulsiveness and variation in insula activity responses as measured in a fMRI monetary incentive delay task47.
