Porjesz et al., using linkage analysis on a large sample mostly consisting of families selected for dense, multigenerational alcoholism, found evidence for linkage between the EEG beta-2 band (a quantitative trait derived by multivariate analyses of spectral band power) and a region on the short arm of chromosome 4 harboring a set of GABAA receptor genes. Since inhibitory GABA-ergic interneurons have been implicated in the generation of fast cortical oscillations, this finding lends itself to a plausible mechanistic interpretation. The authors concluded that, based on pharmacological data, the GABAA alpha-2 subunit may be the most likely candidate for their linkage findings (Porjesz et al., 2002a). Further analyses using improved genetic analytical approaches led to significant findings on chromosomes 1, 4, 5, and 15 with evidence of epistatic interaction between these loci(Ghosh et al., 2003). It is important to note that linkage analysis is just the first step to gene identification, since it only provides a probable chromosomal location of gene(s) influencing the phenotypic trait. Single-nucleotide polymorphisms (SNPs) offer an opportunity to test for association between the beta EEG traits and
