Brain Activity Differs in Men and Women During Genital Arousal
In men watching erotic movie clips, brain and genital responses are less coupled.
Most studies that examine the neural correlates of genital arousal have focused on men. A recent study combined functional MRI (fMRI) with infrared thermal imaging to directly compare male and female responses to sexually arousing movie clips. The findings, published in the February issue of the Journal of Sexual Medicine, show that the correlation between brain and genital responses is weaker in men than in women.
“The biggest misunderstanding that sex researchers are trying to correct is the notion that women have some sort of disconnect between their minds and their bodies,” said Mayte Parada, a couple and family therapy intern at the McGill University Sexual Identity Centre in Montreal, Canada. “My study shows that there may be different neural processes that are more closely associated with genital responses in women than in men, not that women use more brain power.”
In the study, 20 men and 20 women watched erotic video clips while undergoing an fMRI brain scan. At the same time, their genital temperature was continuously monitored by a thermal imaging camera. Past studies have shown that thermography is a reliable and valid measure of blood flow changes related to sexual arousal. The technique allows men and women to be tested using the same paradigm and equipment to assess sex differences.
Although similar brain regions were activated during sexual arousal in both the men and the women, the women's brains showed more extensive activation. Multiple brain regions in the women also showed a stronger relationship with genital responses, while no brain region in the men showed a stronger relationship with genital responses compared with women’s.
“It does not mean that women think more or require more intellectual stimulation when sexually aroused,” Parada said. “However, it could mean that for women what's going on in the brain during sexual arousal is really important for the physiological responses and vice versa.”
The findings surprised the authors because most previous research showed that correlations between genital response and subjective arousal are stronger for men. For now, the reasons for the discrepant findings are not entirely clear. “The broad implication is that much more work needs to be done. Most laymen think we know more about the science of sex than we actually do,” said Nan Wise, a certified sex therapist based in West Orange, New Jersey. “But the big impact of this study is that successfully coupling methods to measure both brain and body blood flow, going forward, may help clarify some of the sex differences.”
The study had several limitations. For example, sexual arousal and associated brain activity might be affected by the laboratory environment. “The main weakness of the study is whether it was truly possible to match the precise timing of the temperature blood flow measure with the brain activity measure,” Wise said. “In other words, they attempted to see which brain regions had increased activity at specific times when the blood flow to the genitals increased, but it might not have been possible to accurately sync the two measures for complicated methodological reasons.”
According to Wise, new methods of data analysis and interpretation known as effective connectivity may help tackle some of the questions about how the sexual brain works, and what might be going wrong for people with sexual dysfunctions.
“By exploring which brain regions are connected, working together, driving each other in terms of actual functioning, we should get more answers about how the brain works in human sexual response,” she said. "Understanding the sexual pleasure brain should give us some keen insights into the clinical states associated with anhedonia -- or the difficulty experiencing pleasure -- which underlies addiction, anxiety disorders and depression.”