The present investigation consisted of an analysis of EEG parameters in a large population-based sample of adolescent and adult participants from three independent cohorts of the Minnesota Center for Twin and Family Research (MCTFR) who had been genotyped for 527,829 SNPs. The analysis plan for the GWASs in this special issue is described in depth in Iacono, Malone, Vaidyanathan, and Vrieze (2014). In brief, we examined the power of the EEG signal in four frequency ranges as well as the peak frequency of the alpha rhythm using a four-pronged approach: estimate the heritability of each EEG parameter using twin and twin-family biometric models; estimate the total genetic variance in each parameter accounted for by all SNPs in aggregate by means of genome-wide complex trait analysis (GCTA; Yang, Lee, Goddard, & Visscher, 2011); assess associations between each individual SNP and EEG parameters in a GWAS; and assess associations between individual genes and EEG parameters by aggregating the effect of all SNPs in a gene using VEGAS, a versatile gene-based test for association studies (Liu et al., 2010). Analyses of individual SNPs
