Interhemispheric asymmetry of EEG alpha activity at rest and during the Wisconsin Card Sorting Test: relations with performance

There are conflicting results regarding the functional asymmetry of the pre frontal cortex. Spectral power analysis of electro encephalo graphic (EEG) activity can provide important clues about the cortical mechanisms. In this study, interhemispheric EEG alpha power asymmetry of healthy individuals w as investigated during the execution of the Wisconsin Card Sorting Test (WC ST) and during rest. We analyzed alpha-1 (8.6-10.2 Hz) and alpha-2 (10.9-12 .5 Hz) bands separately and found some evidence to indicate that lower and upper alpha bands reflect different cortical processes. On the other hand, greater alpha power during resting correlated with higher performance on th e WCST. The lower left frontal alpha power during WCST correlated significa ntly with the higher WCST performance. However, greater bilateral parietal alpha power during WCST correlated with higher performance. Significant cor relations between EEG activity and WCST performance were, in general, restr icted to lower alpha power, both at rest and during the task. These finding s are discussed with regard to attention processes reflected by lower alpha activity. (C) 2001 Elsevier Science B.V. All rights reserved.