10 Interesting Facts About Your Brain on Sex

It might not look like the sexiest body part, but it really is.

January 15, 2013  |  

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Remember the Seinfeld episode where Jerry’s penis has an argument with his brain and loses? It’s a classic: we’ve all been torn between love/lust and logic. (If you haven’t, check for a belly button because this isn’t your home world.) This brilliant bit of comedy is totally relatable but a little misleading in one way: the brain is the one that sends signals to the penis in the first place. It’s pretty reliably running things, IMing the other body parts like crazy, regulating chemicals, making calculations and responding to stimuli, half the time without you even knowing about it. There’s a reason “the brains of the outfit” denotes someone who is really in charge. 

So why does the brain sometimes signal us to do stupid things, especially in regard to sex and relationships? Isn’t that a little like one conjoined twin punching the other in the mouth? How does the brain decide who attracts us? What is it doing behind our backs, and how do we change as we mature?

Here are some of the ways the joys, quandaries and mechanics of sex are all in your head.

1. Size matters.

The preoptic area of the hypothalamus, which regulates mating behavior, is a little more than twice as big in men as it is in women and has twice as many cells. Medical Net says difference starts to show up when we’re about four years old. 

2. Location. Location. Location.

The male brain devotes twice as much real estate to sex as the female brain. They think about it, but do they listen about it? 

Some men certainly do, and maybe more will now that there’s visible evidence of what some women have been trying to tell them for quite some time: there is a great deal of difference between vaginal and clitoral stimulation. Now you can see it. Researchers at Rutgers University used an MRI to map what locations on the sensory cortex correspond to the vagina, clitoris and nipples. All three clearly in very different locations in the brain. (Click and scroll down for the images.)

The fact that nipple stimulation lit up the areas corresponding to the genitals as well as the chest area seemed to come as a surprise. Linda Geddes of New Scientist quotes researcher Barry Komisaruk as saying, “When I tell my male neuroscientist colleagues about this, they say: ‘Wow, that’s an exception to the classical homunculus,'” he says. “But when I tell the women they say: ‘Well, yeah?’ It may help explain why a lot of women claim that nipple stimulation is erotic, he adds.”


Anyway, those images are pretty spiffy, and they’re ripe for a new line of greeting cards. Valentine’s Day is coming and those hearts and cherubs need a break. 

3. In what part of the brain do we find the “Not tonight, honey” headache?

It was a comic trope of the olden days for women who didn’t want sex to opt out due to headache, but it turns out migraine sufferers seem to have a higher libido than other sufferers. LiveScience reported on a 2006 study from the Wake Forest School of Medicine which found that people who suffer from migraine headaches reported a sex drive about 20% higher than those prone to regular tension headaches. The key might be the neurotransmitter serotonin. High serotonin levels are associated with low libido; the researchers reported that migraine sufferers had low serotonin levels. And About.com reports that a 2001 survey of women who had sex during migraines 30% noticed a decrease in pain, 5.3% said the pain increased, and 17.5% reported the pain went away.