There are differences in cerebral activation between females in distinct menstrual phases during viewing of erotic stimuli: a fMRI study

There is evidence that men experience more sexual arousal than women but also that women in mid-luteal phase experience more sexual arousal than women outside this phase. Recently, a few functional brain imaging studies have tackled the issue of gender differences as pertaining to reactions to erotica. The question of whether or not gender differences in reactions to erotica are maintained with women in different phases has not yet been answered from a functional brain imaging perspective. In order to examine this issue, functional MRI was performed in 22 male and 22 female volunteers. Subjects viewed erotic film excerpts alternating with emotionally neutral excerpts in a standard block-design paradigm. Arousal to erotic stimuli was evaluated using standard rating scales after scanning. Two-sample t-test with uncorrected P<0.001 values for a priori determined region of interests involved in processing of erotic stimuli and with corrected P<0.05 revealed gender differences: Comparing women in mid-luteal phase and during their menses, superior activation was revealed for women in mid-luteal phase in the anterior cingulate, left insula, and orbitofrontal cortex. A superior activation for men was found in the left thalamus, the bilateral amygdala, the anterior cingulate, the bilateral orbitofrontal, bilateral parahippocampal, and insular regions, which were maintained at a corrected P in the amygdala, the insula, and thalamus. There were no areas of significant superior activation for women neither in mid-luteal phase nor during their menses. Our results indicate that there are differences between women in the two cycle times in cerebral activity during viewing of erotic stimuli. Furthermore, gender differences with women in mid-luteal phases are similar to those in females outside the mid-luteal phase.