Sexual arousal in response to sexual stimulation appears simultaneously or separately in the brain and genitalia. As women experience less correlation between genital sexual arousal and feelings of sexual arousal than men do, it is reasonable to detect brain response or activation to sexual stimuli to evaluate or understand the physiology of sexual function and dysfunction.
The fMRI technique is used to document areas of brain activation using a wide variety of motor, sensory or cognitive tasks, including studies of male and female sexual arousal. The activated brain areas demonstrated by fMRI during sexual visual stimulation are the frontal lobe, cingulate gyrus, insula, corpus callosum, caudate nucleus, globus pallidus, inferior temporal lobes and thalamus.[6–10,13] Arnow et al. used fMRI to confirm the activated brain area during penile erection by visually evoked sexual stimulation, and reported that activation of the right insula and inferior portion of the insula, caudate nucleus, cingulate gyrus, posterior temporal lobe and hypothalamus is associated with penile tumescence. However, data addressing sexually aroused females are relatively limited. Using fMRI, Park et al. first described female brain activation during sexual arousal showing activation in the inferior frontal lobe, cingulate gyrus, insula, corpus callosum, thalamus, caudate nucleus, globus pallidus and inferior temporal lobe.
In our study, overall, the activated areas on fMRI during sexual arousal were similar to those reported by previous studies. We did not observe any significant activation of the amygdala, whereas the thalamic and hypothalamic areas showed individual variation. These findings differ from other studies. The majority of other fMRI studies of sexual arousal report activation of the amygdala, thalamus and hypothalamus in both men and women, although to different degrees.[6–13] Activation of the amygdala and hypothalamus are more prominent in men than in women when presented with the same sexual stimuli, even when women reported greater sexual arousal.[11,12] The amygdala and thalamus may have a greater role in mediating visual stimuli in male sexual behavior. However, the visual stimuli presented in those studies were universal to both genders and did not consider different preferences between the genders. Therefore, their results may differ from our study.
Conventional AVSs, which are traditionally male-oriented erotic films, have clear limitations when identifying brain activation areas in women. We hypothesized, on the basis of established observations of differing responses to various erotic stimuli and differing conditions to become sexually aroused between men and women, that women would require AVS more suited to their own preference in order to properly study female sexual function. As expected, women responded differently to the widely available male-oriented erotic films. We could confirm that—though women are aroused by stereotypical male-oriented AVS—female sexual arousal is more powerfully activated by films that better affect sexual emotions and mood (erotic movies with a concrete story and emotional stimulation). In addition, men showed more activation on fMRI when viewing stereotypical, male-oriented erotic films. Preference for a specific type of visual stimulation affected brain activation more in men than in women. We suggest that this is because women are more sensitive to non-visual or emotional stimulation and they easily link current stimuli to recalled memory. According to Jansen et al., a woman's ability to imagine herself as the woman in the film was the only factor strongly correlated with her reported arousal. Men also project themselves into the scenario, but may be more likely to objectify the actors. The presence of this gender difference is interestingly supported by a study of fMRI in male-to-female transsexuals. Male-to-female transsexuals responded more similarly to female control subjects than male control subjects during viewings of erotic stimuli.
Sexual arousal is conditional. Relative to men, more factors contribute to female arousal: personal relationships, family concerns, child issues, emotional status, physical conditions, menstrual cycles, environments and others. Women also have different levels of arousal depending upon menstrual cycles. In the ovulatory phase, female sexual arousal may be enhanced relative to other menstrual phases. Therefore, gender differences in arousal to sexual stimuli should be considered in the clinical setting. Erotic films for AVS to diagnose sexual dysfunction usually contain male-oriented clips of sexual stimulation. This may not be a suitable method for inducing sexual arousal in women to differentiate and diagnose female sexual dysfunction, because these video clips do not consider women's sexual characteristics and preferences. Results of analyses intended to differentiate female sexual dysfunction by their response to an improper sexual stimulation may not reflect the patient's actual sexual problem.
This study confirmed the different areas of activation between men and women. Gender difference was observed according to the type of visual erotic stimulus and by differential activation on fMRI.
Many contributing factors can affect sexual preference, such as education, social relationships, cultural background, personal sexual preferences, personal history or cognitive processes.[9,10] It is not yet clear whether differences in preference between the genders are acquired or innate. The presence of those differences should not be ignored. We suggest that gender differences in sexual arousal on fMRI to different visual sexual stimuli may be the combined product of social and biological influences on cognitive processes that direct the perception and assessment of these stimuli.
This indicates that women need different visual sexual stimulation to be aroused, and clinicians should consider this difference when applying the AVS method to evaluate and diagnose female sexual dysfunction.
This study was partially supported by a grant from Ewha Womans University Mokdong Hospital Clinical Research Grant 2008. We would like to thank Mr Keun Tack Ryu and Dr Su Hyun Kim for their technical support and for evaluating and analyzing fMRI data.
Int J Impot Res. 2013;25(4):138-142. © 2013 Nature Publishing Group