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Pajiba Dirty Talk: The Erotic Brain

By Dr. Pisaster | Pajiba Dirty Talk | August 11, 2011 |

By Dr. Pisaster | Pajiba Dirty Talk | August 11, 2011 |

It’s a bit amazing, when you think about it, how much of our knowledge of the human body comes from studies of only one sex. The idea that male is the “default” of humanity is so deeply entrenched in our culture that it often literally does not occur to doctors and scientists to include women in studies of basic human functions, and when they are included it is often in ways that are incomplete. Our knowledge of the sensory cortical map (that’d be the areas of the brain that respond to stimuli, also known as a homunculus ) of human genitals is based almost entirely on studies of men. Where women’s genitals have been mapped, the focus has been on the clitoris, as it’s the anatomical equivalent of the penis and follows the same neural pathway. The nerves involved in vaginal and cervical stimulation are different, however, and their stimulation has not been mapped on the human brain in the same way that penile and clitoral stimulation have. A new study in this month’s Journal of Sexual Medicine aims to fill in this gap in our understanding of the human body.

The study, conducted by researchers from Rutgers University, University of Medicine and Dentistry New Jersey, and University of West Scotland, involved taking fMRI images of the brains of eleven women between the ages of 23 and 56 while they stimulated themselves in various ways. The stimuli included rhythmic tapping of the clitoris, stimulus of the vaginal anterior wall (done using “the participants own stimulator,” i.e. her own personal dildo), cervical stimulation using again a tool provided by the participant. The researchers also looked at the cortical response to nipple stimulation, and stimulation (by someone else) of the participant’s thumb or toe.

The stimulation of the non-sexual parts of the body - the toe and thumb - mapped to the same parts of the brain as those previously mapped in men, but the genital stimulations were different. Clitoral, vaginal, and cervical stimulation all lit up distinct parts of the region of the brain known to respond to genital stimulation. There was some overlap between the vaginal and cervical stimulation, but that’s not surprising given that it’s kind of hard to reach the cervix without stimulating the vagina as well. The researchers attribute the difference in the regions of the brain activated by the different stimuli to the fact that different sensory nerves connect to each of these parts of women’s genitals - the pudendal nerve for the clitoris, the pelvic nerve for the vagina, and the pelvic, hypogastric, and vagus nerves for the cervix. The researchers also found (unexpectedly!) that nipple stimulation also activated the same parts of the brain as genital stimulation at least for some of the subjects. In news reports at least one of the study authors emphasizes how surprising this finding was (though they must have suspected something given that they chose to look at nipples as opposed to, say, ears), giving the world the impression that neurologists never interact sexually with actual women outside the laboratory (in fact, several of the study’s authors are women, but nobody’s quoting them on this).

The more interesting result from this study, in my opinion, is the fact that vaginal, clitoral, and cervical stimulation are distinct in the regions of the brain they activate. The number of subjects in the study is low and it’s impossible to tell how much variation there is among women in how we react to various forms of stimuli (the researchers only present representative data, they don’t report any comparison between subjects), but there are so many myths and disagreements out there about how women experience sexuality, based mostly on anecdotal evidence and personal experience, that it’s nice to see some scientific proof that not all forms of genital stimulation are the same. Some people insist that vaginal orgasms are better than clitoral orgasms while others are adamant that vaginal orgasms don’t even exist and women who experience them are actually having clitoral orgasms but are confused about the source. The truth is that we simply can’t make conclusions about all other women based on our own experiences, especially when it comes to something as diverse as women’s physiology and sexual experiences. This study didn’t look at the difference in orgasms induced by stimulation of different areas, but it does demonstrate that the neural networks that react to stimulation of these areas, while they overlap, are not identical. The results imply that experiences of vaginal stimulation are not necessarily caused by indirect clitoral stimulation.

Of course, fMRI images of a small group of women say nothing about objective experiences of sex. While nipple stimulation may link to the same brain areas as genital stimulation of some women (and probably at least a few men) and provide a wonderful erotic charge, there are lots of women for whom nipple stimulation does nada (and here’s hoping this study doesn’t exacerbate the nipple-and-genitals-only form of foreplay that so many clueless men believe will always work). Similarly, there’s no reason to assume based on this study that all women are wired to experience orgasmic levels of stimulation from the clitoris, vagina, and cervix (although hopefully at least one of those works at least some of the time). More experiments are needed to see how these networks vary from person to person. Hopefully now that the door has been opened more studies like this one will broaden our understanding of women’s neural networks as well as men’s.

Dr. Pisaster has a doctorate in biophysics, not actually anything sexy. She does however enjoy having sex, reading about sex, and talking about sex. Especially when she’s had a little whiskey.

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Dustin is the founder and co-owner of Pajiba. You may email him here, follow him on Twitter, or listen to his weekly TV podcast, Podjiba.