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"You might well think of your brain as one giant gonad," Kayt Sukel explains in her new book DIRTY MINDS: How Our Brains Influence Love, Sex, and Relationships, which mines the latest neurobiology in an effort to explain why we behave the way we do in sex and love. The author did her part for science earlier this year when she got her brain scanned during an orgasm. Well, two orgasms: Her first was too short. She had to do perform the feat twice in front of Rutgers University researchers, all while strapped down behind a mesh plastic mask to keep her head still during the fMRI. Ms. Sukel spoke with The Globe and Mail from her home in The Woodlands, Texas.

The study of love and sex via neuroscience is relatively new – 1990s onward?

There were some forays before that but the scientists wouldn't have called it love. They would have called it pair bonding or attachment and this work would have been done in animal models. The application to humans didn't come until the mid-nineties.

At a 1996 symposium in Stockholm, a group of scientists came up with this working definition for love: a "life-long learning process." What about epigenetics and our behaviour in love?

For so long, science has vacillated between nature and nurture. What we're realizing is that you can't tease the two apart. Whether you're talking about the behaviour of a cell – which is what a lot of the epigenetics research is right now – or the behaviour of a person, it's hard to separate the biology from the environment. The environment plays such an important role: These lasting marks are made right on your genome.

"With every new experience, every new item learned, every new relationship, there are subtle changes to our synapses," you write. So past unions – exes, in effect – mark up our genes and affect the way we behave in future liaisons?

It's entirely possible. Everything in the world has the power to change our synapses, how we learn and ultimately how we behave.

A few surprises from the book: More women have orgasms with partners they aren't seriously involved with, this from the National Survey of Sexual Health and Behavior.

Isn't that crazy? Here you have women reporting they have more orgasms with novel partners. We have a lot of biases when it comes to relationships. In the past we've used little bits of science we picked and chose to reinforce those biases: The idea that women are more emotional and men are players. That's not necessarily true and the science doesn't back that up. An Australian researcher did a longitudinal study on menopause looking for a hormonal smoking gun as to why women at this age are less interested in sex. What they found was that the women who were having the most sex were the ones who had a new partner.

Another unexpected finding, this one from an Emory University study regarding porn: Women rated pornographic images as subjectively more sexually arousing than men did.

Women have been taught to believe they're not supposed to watch porn, that it's not supposed to be part of female sexuality and that there's something anti-feminist about it. What scientists have discovered is that the brain is really hardwired for porn. We are very interested in sexual images, much in the way that we're interested in pictures of food.

What lit up in women's and men's brains when they looked at porn?

The researchers saw higher activation in the men in both the amygdala and the hypothalamus, two areas involved in sex and emotional processing. When they examined what the participants were actually looking at using eye tracking software, there was no significant difference between men and women. Nobody really liked the close up, crazy genital shots.

Does it surprise you that men said that?

A little bit. I think it's something that needs more study.

One study found that activation in male and female brains during climax is fairly uniform, aside from some mechanics. Same for passionate love, which triggers the same parts of the brain across the board, for straight and gay men and women alike.

For me it proves that love is love no matter who happens to be in love.

Tell me about your own orgasm tracked via fMRI.

I had no idea how much of my brain would be activated: It was lit up like a Christmas tree. Orgasm gives your brain one hell of a workout and it's probably very good for you, up there with diet and exercise, to keep up optimal brain health. Many studies have shown aging people who have better cognitive abilities are all still having sex.

You describe the brain as a giant gonad and point out you don't even need genital stimulation: Wet dreams are a case in point, as are people with spinal-cord injuries who can climax. Which brings us to "thinking off."

Thinking off is the ability to think yourself into an orgasm. Instead of using your hands to touch yourself or having a partner do it, you can arouse yourself enough by fantasy and top down control of the brain to achieve actual physical orgasm. We don't know how prevalent it is but it may be possible that we're all capable of it, but just never figured out how.

Tell me about your friend, "Trixie."

She has a very respectable corporate job and told me she did it all the time, during conference calls at work to pass the time. She was very kind and allowed me to observe despite a lot of embarrassment I think on both of our parts. It's a good enough orgasm that she does it quite often. What researchers have seen when they've put people who can think off into fMRIs is that the brain looks pretty much the same as when people are "touching off."

Let's turn to sex addiction, under consideration for the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders next year as "hypersexuality." Brain chemistry-wise, who is most at risk for this malady?

Lique Coolen [a neuroscientist at the University of Michigan]looked at animal models and found damage in the prefrontal cortex resulted in rats compulsively seeking sex. Male rats that have this damage can't help themselves. With one gene variant, DRD4, it seems there is more novelty seeking, but that doesn't mean it has to express itself with hypersexuality. The person can be an adrenalin sports junkie or get thrills from winning eBay auctions.

Some think it's all about self-discipline but it's becoming clear there is more to the story. Kristie, a woman I spoke with, identified as both a love and a sex addict. There's an intrigue and she can't get enough of it. Wolfram Schultz, a neuroscientist at the University of Cambridge who studies reward and risk processing, said our brain system's set up so that anything can become addictive.

Why does "love addiction" come with some partners and not others?

Why do some people affect us and make us absolutely nuts so that our family and friends are all saying, "Get yourself woman, you are nuts!" and then other people are as comfortable as a nice warm bath but they're not making you break ties with your family or risk losing your job because you're coming in late every morning. It has a lot to do with chemicals. Our bodies give off a lot of information that other people can unconsciously process. Maybe that person is an ideal genetic mate for offspring. That would certainly satisfy evolutionary scientists.

On the other end we have successful long-term couples: Those still passionately in love after decades showed activated dopamine-rich reward areas in their brains, scientists have found.

Charles Snowdon's study from the University of Wisconsin, Madison, involving cotton-top tamarins found that strong couples had higher levels of oxytocin, which corresponded with certain behaviours: men getting more sex and women getting more cuddling. I hate that it's a total stereotype and yet there's something very interesting in the idea that these couples gave partners what they needed. Neurobiology cements the idea that an active sex life is important to our relationships. In terms of maintaining a bond you have to have that dopamine release and sex is your fast track.

These sci-fi notions of controlling our urges with oxytocin sprays, pheromone potions and "love vaccines" are bunk given how nascent neurobiological studies are in this area, you write.

And yet people are clamouring for it – I know a lot of smart people who really believe that $90 pheromone cologne is doing something for them. Part of me says what's the harm, except that chemicals such as oxytocin and vasopressin are also important to blood-vessel dilation and maternal behaviours. We may actually influence how our bodies make these things. I wouldn't want to mess with that.

Ultimately, science still provides few answers about our lusty behaviours: It's a stew of biology, context and individuality. "The study of something like love is very complicated and cannot be reduced simply to the neuronal level," says Harvard Medical School neuroscientist Jill Goldstein.

At first it annoyed me: I wanted some actionable advice. The more I thought about it, the more I appreciated not knowing more. Good science asks as many questions as it answers. This scientific work challenges many notions you find in self-help books, which promote one-size-fits-all answers to relationships and suggest you can't be happy unless you follow those rules.

Are you with someone now?

I am not. I'm dating.

How does this stuff affect the way you look at your dates? Are they guinea pigs?

Right now I am much more likely to listen to what my gut is telling me about a person. In my 20s, I would have looked at someone and said, "But he's got such a great job and he's so good looking." Now even if he's great on paper, I listen to what my gut has to say.

This interview has been condensed and edited.

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