Brain Activation Patterns during Sexual Arousal: A Comparative Time-Course Functional Magnetic Resonance Imaging...

This study used functional magnetic resonance imaging with time-course analysis to compare the temporal dynamics of brain activation patterns associated with visual sexual arousal among postoperative female-to-male (FtM) transgender individuals, men, and women.

A total of 57 volunteers participated in this study, including 17 FtM transgender individuals undergoing cross-sex hormone therapy, 20 cisgender men, and 20 premenopausal cisgender women.

The levels of free testosterone (free-T) and estradiol in FtM transgender individuals were more similar to those in cisgender men than in premenopausal women. The time-course analysis of brain activity while viewing a 9-minute erotic video revealed distinct patterns of blood-oxygenation-level-dependent (BOLD) signal changes across the three groups: FtM transgender individuals showed the greatest BOLD signal changes between 4 and 5 minutes; men's group between 2 and 3 minutes; and women's groups between 5 minutes 30 seconds and 6 minutes 30 seconds. The between-group analysis showed differential brain activity in the insula and caudate nucleus among the three groups. Compared to women, men showed significantly higher activities in both regions, whereas FtM transgender individuals exhibited significantly higher activity only in the insula, but not in the caudate nucleus (p<0.05). Free-T levels were positively correlated with BOLD signal changes in the insula and caudate nucleus.

These findings suggest that both the brain activation patterns during visual sexual arousal and the hormone levels in FtM transgender individuals more closely resemble those of cisgender men than cisgender women. Our findings would be helpful for further understanding of the interrelationship between gender identity and biological sex in FtM transgender individuals by examining time-resolved brain activation patterns in connection with sex hormone levels.