A twin study of genetic influences on the acute adaptation of the EEG to alcohol

A two-dose alcohol challenge protocol was used to study genetic influences on the acute adaptation of the EEG to alcohol in 53 monozygotic and 38 same -sex dizygotic Caucasian twin pairs averaging 30 years of age. Equal doses of alcohol were administered at 10:00 and 11:00 AM, yielding mean. peak bre ath alcohol concentrations of 0.057% and 0.099%, respectively. Eyes-closed, resting EEG was recorded four times: at baseline; on the ascending limb of the overall experiment at a breath alcohol concentration (BrAC) near 0.06% ; on the descending limb at a BrAC near the value when the subject's EEG wa s obtained on the ascending limb; and, finally, when the BrAC fell to 0.02% . Genetic analyses of log-transformed values of total spectral power (L10TS P) and spectral band power (L10SBP) were performed on EEG spectra averaged across all 17 scalp lead locations. After adjusting for body weight, a sign ificant fraction of population variance In L10TSP was attributable to genet ic influence: H-2 values for TSP were 0.73, 0.72, and 0.73 at the three pos talcohol EEG recordings, respectively. Similar findings pertained to each L 10SBP at each postalcohol recording, except for the delta band. The change in postethanol EEG power was examined for evidence that genes influence acu te adaptations In brain function. Descending-minus-ascending limb L10TSP wa s normalized by the individual's ascending limb L10TSP to minimize nonalcoh ol-related effects that, can influence both measurements. Earlier analyses of the same sample's initial EEG response to alcohol noted a substantial in crease in the ascending limb EEG power, compared with baseline, Thus, posit ive values of the postethanol change denote a progression away from baselin e attributable to acute sensitization to alcohol; negative values signify a return toward baseline values suggesting acute tolerance to alcohol. Genet ic analysis of the normalized difference in L10TSP had a highly significant H-2 value of 0.70, indicating that both acute tolerance and acute sensitiz ation to alcohol may represent adaptations reflecting substantial heritable influence. Slightly smaller, but significant values of H-2 for the normali zed difference in L10SPB were observed for delta, alpha-slow and beta-slow frequency bands. In contrast, H-2 for the differences between the final and ascending limb EEG power were not significant, except for the theta band. Thus, heritable drowsiness may have contributed to detection of genetic inf luences on acute adaptation, but represent a potential confound only in the theta band.