Brain Plays Major Role in Women's Sexuality

But the brain, instead of peripheral organs, may play the key role in female sexual dysfunction.

Medical researchers reported that more than 40% of women, ages 18-59, experience sexual dysfunction, with lack of sexual interest, hypoactive sexual desire disorder (HSDD) being the most typically reported complaint. While critics question the validity of this diagnosis, a multidisciplinary team from the Stanford University School of Medicine and Stanford Hospital & Clinics (Stanford, CA, USA) is conducting an objective investigation of such problems, including Bruce Arnow, Ph.D., professor of psychiatry and behavioral sciences, and Leah Millheiser, M.D., director of the Female Sexual Medicine Program and clinical assistant professor of obstetrics and gynecology.

The trial is the first to compare brain-activation patterns of females who have HSDD with those who do not. Sixteen women diagnosed with HSDD, combined with 20 normal control subjects, took part in the study. All participants identified themselves as heterosexual. Study precipitants were shown erotic video segments interspersed among footage of female sporting events. These segments were separated by tranquil sequences of such subjects as flowers, waves, or mountains to bring the women's brains to a resting state between more active segments. Their brain activity was monitored by functional magnetic resonance imaging (fMRI) scanning, which allows the activity of different brain regions to be evaluated in real time. The women also reported their subjective levels of sexual arousal throughout the viewing. Meanwhile, the researchers collected objective measurements of the women's level of genital arousal.

The study's findings demonstrated that activity patterns throughout most of the brain were more or less identical among the HSDD and control groups, with a few notable exceptions. There was a bigger increase in relative activity in three brain areas of HSDD women--the medial frontal gyrus, right inferior frontal gyrus, and bilateral putamen--compared with the control subjects when shown the erotic clips. In another brain area--the bilateral entorhinal cortex--the opposite effect occurred. This finding establishes specific locations in the brain where activity in women with HSDD is altered in comparison with women not reporting this problem.

Two of the brain areas where the HSDD women had increased activity (the medial frontal gyrus and right inferior frontal gyrus) have been previously associated with, respectively, heightened attention to one's own and others' mental states, and suppression of one's emotional response. The research suggests that increased attention to one's own responses to erotic stimuli plays some part in the sexual dysfunction. The increased activation in the entorhinal cortex observed in the control individuals may correlate with an improved ability among women with no sexual dysfunction, compared with HSDD women, to lay down emotional memories related to sexual events.

The study, according to the researchers, could be showing how paying too much attention causes inhibition of sexual desire--or how the lack of desire in a sexually charged situation causes heightened self-consciousness. "The results of this study provide yet another valuable tool for understanding the complexity of female sexual function as it relates to desire," Dr. Millheiser said. "The next step is to translate this information into the clinical realm, specifically as it relates to cognitive and pharmacotherapeutic approaches."

The results were featured in the January 23, 2009, issue of the journal Neuroscience.

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