Background: In this study, the magnitude and spatial distribution of theta power in the resting EEG were examined to explore the changes in the neurophysiological status of the alcoholic brain. Some state- and trait-related issues of theta power increases in the EEG of alcoholics were also examined.
Methods: Absolute theta (3-7 Hz) power in eyes-closed EEGs of 307 alcohol-dependent subjects and 307 age- and gender-matched unaffected controls were compared by using a repeated-measures ANOVA for the entire region and three subregions (frontal, central, and parietal) separately. Supplementary to the main analysis, the effect of three clinical variables on absolute theta power was examined separately for each gender by using correlation and regression analyses. Gender differences in the theta log power difference between alcoholics and controls were explored by using regional repeated-measures ANOVA.
Results: Increased absolute theta power was seen in alcohol-dependent subjects at all scalp locations. The theta log power increase in male alcoholics was prominent at the central and parietal regions and in female alcoholics at the parietal region when compared with the respective matched controls. Correlation of drinking variables with log theta power exhibited no group-specific differences.
Conclusions: Increased tonic theta power in the EEG may reflect a deficiency in the information-processing capacity of the central nervous system in alcoholics. The theta power increase may also be an electrophysiological index of the imbalance in the excitation-inhibition homeostasis in the cortex. It is likely that the theta power increase is a trait-related phenomenon and is expressed to differing degrees in the two genders.