Sexy Neuroscience II

a.k.a. The Revised Homunculus

A new study has mapped brain sensory fields for the clitoris, vagina, uterine cervix, and nipples – and it turns out that nipple stimulation activates very similar responses to those evoked by genital contact.

Do you have any idea how hard it was to keep this whole post SFW?

Yes, that’s right: fMRI scans are, once again, teaching men how to be better at sex – while telling women things they already knew. More surprising (or maybe not so surprising, actually) is the fact that most of these sensory linkages had never been mapped in the female brain before.

Here’s how it breaks down: by measuring activity patterns in the somatosensory cortex, the Journal of Sexual Medicine reports, a team led by Rutgers University physician Dr. Barry Komisaruk found that stimulation of the vagina, clitoris, and cervix each triggered different sorts of neural responses – and that nipple stimulation triggered responses in two areas:

Vaginal, clitoral, and cervical regions of activation were differentiable, consistent with innervation by different afferent nerves and different behavioral correlates … Nipple self-stimulation activated the genital sensory cortex (as well as the thoracic) region of the homuncular map … [this] was unexpected, but suggests a neurological basis for women’s reports of its erotogenic quality.

Unexpected for Komisaruk, maybe; but not for anyone in possession of a functional pair of breasts. (For those of you who didn’t know, some women can reach orgasm through nipple stimulation alone.)

“When I tell my male neuroscientist colleagues about this, they say: ‘Wow, that’s an exception to the classical homunculus,'” [Komisaruk] says. “But when I tell the women, they say: ‘Well, yeah?'”

I may be going out on a limb here, but it sounds like those male neuroscientists don’t get out much. Anyway, this is interesting for several reasons – first, because until now, neuroscientists only had a very limited understanding of the cortical response patterns associated with areas that are unique to a woman’s body. Now they finally have some solid fMRI data – pertaining to several important areas – which they can start to build on.

Even more importantly, though, this study marks the latest step in a long transformation of the way the somatosensory cortex is understood. See, there’s a widely popular idea in neuroscience that dates back to the 1950s: the sensory homunculus.  As you can see from the psychedelic-looking picture in that link, the basic idea is that different areas of the body are represented in differently sized and shaped (but well organized) areas of the brain.

Problem is, the homunculus was designed with men in mind – in fact, until a few years ago, there literally was no sensory homunculus designed to map the female body. That all changed in 2004, when Lars Michels at University Children’s Hospital in Zurich, Switzerland used fMRI research to show that the clitoris in the female sensory map was in nearly the same position that the penis held in men’s brains. Yep, that’s right – it took ’em until 2004 to find the damn thing. I imagine the wives and girlfriends of neuroscientists everywhere breathed a collective sigh of relief on that day.

Like many studies backed by well-written grants, this research is only one phase of a continuing clinical program that’ll hopefully bring some therapeutic benefits to women who’ve suffered nerve damage from childbirth or disease. As promising research in neuroplasticity hints, some women may be able to “rewire” damaged sensory maps, and regain erotic and orgasmic sensations they’d lost. Komisaruk says he’d also like to study the neural correlates of the g-spot, because hey, when you’re on a roll…

As this field of study continues to heat up, it looks like we may be on the verge of some exciting new discoveries about how the human brain experiences sexual sensations – and in the interest of science, I’ll stay hard at work keeping you informed about them. It’s a tough job, I know; but somebody’s gotta do it.

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