Menstrual cycle modulation of medial temporal activity evoked by negative emotion.

Previous studies have indicated phase-related differences in HPA activity and amygdala responsiveness in women, such that the response to negative emotional images is reduced during high-estrogen phases of the menstrual cycle. Other research has indicated an opposite effect of exogenous progesterone, increasing amygdala activity at some doses. However, no study to date has assessed the response of the brain's arousal circuitry to negative images during the luteal phase, when both progesterone and estrogen levels are elevated. To address this question, 17 naturally cycling women were each scanned during the early follicular and mid-luteal phases of the cycle, and response to IAPS images was assessed by fMRI. The results indicated significantly increased activity in hippocampus and amygdala during mid-luteal scans when compared to scans in the early follicular phase. These findings suggest that progesterone-mediated effects dominate during the luteal phase, and further suggest that estrogen and progesterone may play opposing roles in modulating the brain's arousal circuitry.