Sex differences in EEG coherence during a verbal memory task in normal adults.

Coherence analysis was applied to the EEG of 15 female and 15 male subjects who had to memorise dichotically presented lists of concrete nouns. The EEG was recorded from 16 scalp electrodes placed in accordance with the 10/20 system. The results show significant gender-related differences in total coherence reactivity due to a greater increase of rest to task coherence in female than in male subjects. Women differed by showing higher coherence reactivity in the right hemisphere for all analysed (theta 1, theta 2, alpha 1, and alpha 2) frequency bands. They also had more extensive task-induced increases of interhemispheric coherence in theta bands in comparison with single changes in male subjects. In women these changes were mainly between the frontal electrodes of the left hemisphere paired with posterior electrodes of the other hemisphere. These findings indicate sex-related differences in functional cortical organisation during verbal memory tasks.