Several studies have taken the approach of examining the entire genome, rather than focusing on a single candidate gene. Linkage analysis uses markers consisting of polymorphisms varying either in sequence or size in samples comprising families. If a marker is coinherited with a trait, the two are said to be linked, and the gene that influences the trait is thought to be located near the marker. However, such markers tend to be widely spaced, and linkage analysis can only identify a chromosomal region, or “hot spot,” and not individual variants. An early analysis found linkage between beta power and a region of chromosome 4 (Porjesz et al., 2002). Subsequent analysis of individual SNPs to determine the source of this signal obtained significant associations between beta activity and SNPs in the gene that encodes the GABA α2 receptor subunit (GABRA2) (Edenberg et al., 2004). A recent case-control study of alcohol dependence obtained significant associations between beta activity and several GABRA2 SNPs (Lydall et al., 2011). Although characterizing EEGs as dominated by beta or not, rather than evaluating quantitative measures of power,
