EFFECTS OF ALCOHOL, AT 2 TIMES OF DAY, ON EEG-DERIVED INDEXES OF PHYSIOLOGICAL AROUSAL

Effects of alcohol consumption (0.8 ml/kg) on sleep propensity, spectr al characteristics of the EEG and self-rated activation in 16 young ma le subjects, were investigated during sessions at each of two times of day (08.00 and 16.00). Within-session, time-related changes in the pa ttern of stage-1 sleep occurrence, and of spectral power in different EEG bands indicated that, irrespective of time of day, physiological a rousal increased as estimated blood alcohol concentration (BAG) was ri sing, and decreased as BAC was falling. Subjective activation was redu ced by alcohol during both phases of the BAC curve. A pattern of reduc ed stage-1 sleep occurrence, higher absolute high alpha power and high er ratings of activation suggested that, irrespective of alcohol condi tion, physiological and subjective arousal was higher during sessions starting at 16.00 than during those starting at 08.00. There were no s ignificant interactions between alcohol and time of day in respect of any dependent variable. However, the degree to which effects reflectin g circadian variation may have been masked by effects of limited sleep restriction prior to morning sessions remains unclear. Subjects repor ted having slept on only 23.5% of occasions when sleep was scored. Com parison of patterns of statistically significant changes in absolute a nd relative power in different bands indicated that the two indices do not provide exactly equivalent information about changes in the EEG.