The acute effect of low-dose alcohol on working memory during mental arithmetic: I. Behavioral measures and EEG theta band spectral characteristics.

OBJECTIVE AND HYPOTHESIS: Task-related EEG changes were studied during the performance of a mental arithmetic task, as influenced by low alcohol dosages with the presumption that even "social" drinking may have detrimental effect.

METHODS: A mental arithmetic task was used in which addition and working memory effort was required. EEG spectra with an emphasis on the theta band, error rate and reaction time were analyzed in 5 (control, task, placebo-task, low-dose task [0.2 g/kg alcohol], high-dose task [0.4 g/kg alcohol]) conditions. Blood alcohol concentrations were measured.

RESULTS: Reaction time was shortest in the placebo condition. No significant alcohol effect was seen for error rate. Task-related significant theta power increase was observed especially in the frontal area and in the left hemisphere which was reversed, although not in a significant way, by alcohol.

CONCLUSION: No detrimental alcohol effect was seen on behavioral indices of task performance. However, the ethanol-induced moderate reduction of the task-related frontally dominant theta increase, probably corresponding to working memory demand, is a modest but clear electrophysiological sign of alcohol effect in this low-dose range.