A candidate gene association study in a sample of young adult females found that 10-repeat allele carriers of 5HTT (serotonin transporter) polymorphisms alleles conferring low transcription efficiency tended to have reduced EEG power, particularly in the gamma frequency band (Lee et al., 2011b). Another study by the same group (Lee et al., 2011a) reported a significant effect of the catechol-O-methyl-transferase (COMT), gene on the strength of the resting EEG spatial connectivity in the left frontal-temporal scalp area measured using the time-frequency mutual information method, such that connectivity strengths increased in carriers of the Val allele which causes a 3- to 4-fold increase in the enzyme activity and, consequently, reduced prefrontal DA levels (Bilder et al., 2004; Tunbridge et al., 2006). In a related analysis utilizing the same sample, the epsilon4 allele of the Apolipoprotein E (ApoE) gene, a known risk factor for cognitive impairments in Alzheimer's disease and normal aging, was associated with reduced EEG power, particularly in the alpha frequency band, as well as weaker inter-regional connectivity in the right hemisphere in a young population aged 19-21 (Lee et
