The acute effect of low-dose alcohol on working memory during mental arithmetic II. Changes of nonlinear and linear EEG-complexity in the theta band, heart rate and electrodermal activity

Objective and hypothesis: Nonlinear and linear methods of EEG-complexity analysis and autonomic measures were used to characterize processes accompanying performance in a mental arithmetic task challenged by low ("social") alcohol doses. It was expected that alcohol in such doses will dampen changes of task-related EEG-synchronization in the theta band, and those of heart rate and electrodermal activity (EDA). Methods: In the mental arithmetic task addition and working memory, effort was required. The EEG, ECG and EDA were recorded in 5 conditions: task, placebo-task, low dose-task (0.2 g/kg alcohol), high dose-task (0.4 g/kg alcohol). Omega-complexity and synchronization likelihood (SL) were computed of the theta band of the EEG. Results: Task-related decrease of the Omega-complexity and increase of the SL was found in the theta frequency band. Following alcohol consumption, these changes did not develop as seen especially for SL in the anterior area, although the significant effects were elicited by task performance. Conspicuous task-evoked increases were observed for ECG and EDA which were even more enhanced by alcohol. Conclusions: Task-induced significant changes of the Omega-complexity and that of SL indicate increased synchrony in the theta band, probably corresponding to working memory effort. Both of these measures proved to be sensitive for the effect of low alcohol dose although these alcohol-elicited changes were not statistically significant. Task-induced heart rate and EDA increases were further intensified by alcohol probably indicating its activating effect on these autonomic measures in the dose range studied. (C) 2009 Elsevier B.V. All rights reserved.