Effect of diazepam on EEG power and coherent activity: sex differences

Benzodiazepine–steroid interactions and sex differences in brain and circulating levels of gonadal steroids, lead to hypothesized differential effects of DZ on EEG in women and men. Coherent activity has been shown to be relevant for binding information into global percepts therefore diazepam effects on EEG correlation and sex differences were assessed in a double-blind crossover study. Healthy males (9) and females (9) received a single-dose (5 mg) of diazepam or placebo. EEG was recorded with eyes open (FP1, FP2, F3, F4, C3, C4, P3, P4, O1, O2) before and 2 h after drug administration in two counterbalanced sessions. DZ selectively increased δ and θ EEG correlation among frontal regions and decreased it between right parieto-occipital ( θ) and fronto-central regions ( α2) in addition to an increase in β2 interhemispheric correlation in men and women. Men showed increased β1 interhemispheric correlation, decreased α1 and increased β power; women showed in addition, decreased θ and α2 power. θ rhythm was more sensitive to DZ in women, whereas interhemispheric correlation was more affected in men. DZ had a sexually dimorphic effect on waking EEG and a disrupting effect on coherent activity, increasing balance among frontal regions and decreasing temporal coupling between anterior–posterior regions. These sex differences might be related to differences in brain organization and activational effects of female gonadal steroids which are higher in women than in men.