Alcohol effects on the heritability of EEG spectral power

To estimate the effects of a moderate dose of alcohol on heritability of the EEG power spectrum, 53 monozygotic and 38 like-sexed dizygotic Caucasian twin pairs (aged 30.0 +/- 7.0 years) were studied. Subjects were asked not to drink alcohol for 2 days and to fast after midnight before a protocol of: (1) a low fat meal at 8:00 AM; (2) a baseline EEG recording; (3) ingestion of alcohol over 10 min, which raised the breath alcohol concentration to 0.057 +/- 0.017% (SD); followed by (4) a postalcohol EEG recording 35.1 +/- 5.7 (SD) min after the start of drinking. One previous study (Propping, P., Hum. Genet. 35: 309-334, 1977) found that heritability (H2), the fraction of total variance in the EEG power that is attributable to genetic influences, increased after alcohol administration. In the current study, H2 of log-transformed, body-weight-adjusted spectral band power increased after alcohol for the theta-, alpha-slow, alpha-fast, beta-slow, and beta-fast bands (from an average of 0.47 to an average of 0.80). The increase in heritability was accompanied by a significant decrease in the within-pair differences of monozygotic cotwins for all of the same frequency bands except beta-fast. Because within-pair differences are expected to contain only environmental factors for the genetically identical individuals, it was concluded that alcohol decreases environmental variation of EEG power spectral density, causing the increase in H2.