Because previous studies suggest that estradiol partially mediates these sex differences, we examined 20 men (low estradiol and low progesterone), 20 women using oral contraceptives (low estradiol and low progesterone), and 20 free-cycling women during midcycle (high estradiol and low progesterone). We used a fear-conditioning procedure, allowing us to separately assess fear recall and extinction recall 24 hours after fear and extinction learning. Skin conductance responses and electroencephalography were recorded during fear recall and extinction recall, and prefrontal oscillations were source localized.
We found elevated fear expression during fear recall and impaired extinction recall, as indicated by increased peripheral arousal (skin conductance responses) and fronto-central theta oscillations, source localized in the dorsal anterior cingulate cortex and dorsomedial prefrontal cortex. Importantly, peripheral arousal and dorsal anterior cingulate cortex theta oscillations were stronger in men and women on oral contraceptives than in women from the midcycle group.
Our data show that neural oscillatory and peripheral correlates of heightened fear expression during fear recall and (impaired) extinction recall do not simply differ between sexes but depend on hormonal fluctuations within women.