This Is Your Brain on Sex (3 page)

Though this line of inquiry seemed very clear to Carter and Uvnäs-Moberg, it was difficult to get respect (and, perhaps more important, funding) to study such ideas experimentally. There was already ample evidence in neuroscience literature to suggest that love was a worthy topic of research. But the scientists never called it such, avoiding it like the dirty word it is. Instead they referred to the related topics of pair-bonding, monogamy, attachment, and mating behaviors. If you read between the lines, there was a lot of information out there, perhaps even enough to make the neuroscientific study of love its own field. Still most professional scientists were afraid to call love by its true name.

There was no sense in talking about the neuroscience of love without a proper working definition—a common standard that scientists across disciplines could use to test and validate hypotheses. Sadly, as fitting (and poignant) as Ted Nugent’s “tire iron” characterization might be as a song lyric, it would be limiting to use as the basis for a credible, replicable scientific study. To that end Carter and Uvnäs-Moberg invited thirty-eight prominent scientists in the field of neurobiology to a meeting at the 1996 Wenner-Gren Symposium in Stockholm titled “Is There a Neurobiology of Love?”

One of the products of that meeting was a definition. Instead of going with Merriam-Webster’s basic statement about love being a case of “strong affection for another,” the group consensus was that love is “a life-long learning process that starts with the relationship of the infant to his or her mother and the gradual withdrawal from the mother with a search for emotional comfort and fulfillment.” This definition was included in the summary report written by the prominent neuroscientist Bruce McEwen.
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It offers more detail than the definition of love as strictly an emotion or a basic mammalian drive, like hunger or thirst—even if it is less romantic than “sweet surrender” or “my first, my last, and my everything.” Though a mouthful, this definition would serve as the standard to which future studies across the neurobiology field could refer.

The meeting also started a renaissance of sorts, a green light for neuroscientists, neurobiologists, and neuroendocrinologists to finally call love, well,
love.
This allowed them to start studying the nuances of this human phenomenon from the perspectives of brain and biology. Two years later many of the meeting’s prominent attendees published studies in a special issue of the journal
Psychoneuroendocrinology
on topics ranging from the evolutionary antecedents of love to the physiological consequences of withholding it. With such respected scientists backing the concept, researchers could more easily study the
l
-word within the space of the brain and neurobiology.

Sexy Baby Banning

Fast-forward ten years. Many great studies concerning neuroscientific aspects of that “life-long learning process” we call love were published in the late 1990s, with a great number appearing in high-profile journals like
Nature
and
Science.
Brains, it seemed, have quite a bit to do with love—certainly far more than do our proverbial hearts. While working on a story for a neuroscience website, I accidentally stumbled across McEwen’s meeting report. A simple misclick on a library database brought me to it, and even though it was completely off-topic I was compelled to read it.

Maybe I was drawn to the question raised in the title, “Is there a neurobiology of love?” It was not a subject I’d had occasion to study before. Maybe it was the fact that it was written by McEwen, an acclaimed neuroscientist from Rockefeller University. His work had impressed me since I was a graduate student. Maybe I was just procrastinating. I might well have read the phone book as an excuse to take a break that muggy afternoon. Or maybe it had something to do with my sleep deprivation. Did I mention I had recently become a mother?

If there is a stereotype
of a new mom—think bedraggled, beleaguered, and baggy-eyed—I fulfilled it, and then some. From the stains on my shirt to the state of my house, there was not one part of my life left untouched by the effects of motherhood. As much as I do not subscribe to the notion of “mommy brain,” or the idea that motherhood makes you stupid, I have to admit that I sometimes wondered what was going on upstairs. But honestly, what had changed the most—somewhat inexplicably—since becoming a mother was my marriage.

The arrival of my son had completely altered my relationship with my husband. Though I certainly expected my marriage to change once we had children, I was not prepared for a complete loss of intimacy. We had been a tight-knit team, albeit a motley one, but now we were satellites in separate orbits, crossing paths only when it came to our child. My friends with kids assured me that the situation was natural and would right itself over time, after the shock of our new addition wore off. One friend, a mom of three, went beyond that: “You can’t expect to feel the same way about your husband now. Your relationship needs to change so your son can be your focus. Our brains are wired so our kids can come first. It’s an evolutionary thing.”

Her statement stuck with me. I could not understand how an “evolutionary thing,” as she had so eloquently put it, would rule out a nurturing, loving relationship between two adults or an active sex life. Now that I had checked into the breeder category, wasn’t I supposed to keep popping out kids to guarantee propagation of the ancestral line? Sex, if not a little passionate love, was required to fulfill that goal. Perhaps I had missed something.

It was a conundrum. Like most new moms, I was bone-tired. Yet I was enthralled by this small baby boy who somehow managed to brighten each moment of my life as he sucked the energy out of me. Like my friend’s puzzling evolutionary edict, it was a contradiction I could not quite figure out.

As someone who wrote about neuroscience for a living, I began to wonder what role the brain played in what was happening to me. Maybe all of it—my crazy love for my son and my imploding marriage—could be explained by changes in my brain that occurred during and after childbirth. I remained convinced that my husband’s brain may have been altered a little too. Picking
up a copy of a meeting report about the neurobiology of love seemed as good a place as any to start learning more.

Reading McEwen’s report, I was immediately struck by a single line, a quote McEwen added from British researcher and fellow Symposium attendee Nicolas Read:
“If we realized how sexy babies are they would have been banned.”

Frankly, that kind of sentence is an anomaly in the scientific literature. You do not find lines like that in many research papers. Trust me on this one. Most of the papers I read when I’m working on a neuroscience story include lines like, “Aβ deposition stimulates a local immune response by the microglia, which become macrophagic.”
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Though fascinating (once translated into plain human English, that is), it’s not exactly the kind of stuff that makes you laugh out loud.

“It was a quip, obviously,” McEwen said when I asked him why he decided to include it. “But the mother-child bond seems to be such a strong, remarkable phenomenon.” What might researchers learn if they studied such things from a biological and mechanistic perspective? That is exactly what the attendees of the symposium wanted to start doing—as well as take a more mechanistic and biological approach to the study of monogamy, sex, and other love-related behaviors.

Even at such an early juncture in the neuroscientific study of love, McEwen had me at sexy baby banning. It has a certain perverse poetry to it. Not to mention that it resonates strongly for a new, sleep-deprived, and biologically curious mom like myself. To nonparents out there (and admittedly some of the parents too), I am sure this line sounds pretty creepy. Context is everything, after all. But to my mind, it fit. My baby was pretty sexy—much more so than I’d been prepared for. Not in a sweaty, naked-hot-guy kind of way, but in an irresistible, compelling way that had altered my body, my mind, and my life from top to bottom. I had no idea if these changes were due to evolution, neurobiology, or my particular situation, but I wanted to know more about how motherhood—and, yes, love—was facilitating them. So while I became more infatuated with my son each day, I was also just as intrigued by neuroscientific studies that gave me more insight into motherhood, monogamy, sex, and love.

Learning the In’s and Out’s of Love

I have already confessed
that I know nothing about love. I’ve learned that you become much less reluctant to say so as soon as you are familiar with the inside of a divorce lawyer’s office. The disintegration of my marriage was not sudden; it took years and years to circle the drain. You’d think there would have been ample opportunity to correct course during those few years when our unhappiness became apparent. But no matter how deeply I wanted to fix things, I just never found a chance. I doubt my former husband did either. Even in hindsight I cannot tell you where my husband and I went wrong. Just when I knew it would never again be right.

Apparently I have not mastered that “life-long learning process”; despite the fact that my baby, now a charming and curious kindergartener, remains as “sexy” as ever, my search for emotional comfort and fulfillment with a partner continues. Might it have something to do with my hormones? The way my brain is wired? My choice of partner? The length of time we were together? How often we had sex? The way my body, including my brain, changed after having a child? All of the above? It was something I needed to figure out in order to truly move on after my marriage fell apart, not to mention bolster me as I reentered the dating realm.

Like most, I hoped to find some easy answers, some actionable advice that might help me understand my past relationships and, more important, avoid making the same mistakes in the future. With the dating pool beckoning, I hoped that acquiring the right knowledge would make up for developing crow’s feet, a postchildbirth figure, and postdivorce gun-shyness.

My quest to better understand the scientific nature of love started when I stumbled on a research paper and continued as I read all I could find on love, sex, and the brain. It was not enough to satiate my curiosity—I needed to talk to these scientists about their work and the different ways their findings might be interpreted. I had to visit a few labs and see some of the science in action. And surely it couldn’t hurt to participate in a few studies myself.

I learned a lot over the course of this journey. I discovered that the study of love
—in any manner, neuroscientific or otherwise—is a tricky, complicated thing, more so than a natural skeptic like me had ever realized. But despite many enlightening discussions and personal adventures, nothing I experienced offered any surefire intelligence on what the majority of us are hoping to figure out: how to find love and then keep it around for a while. As it so happens, there is no magic formula, no rule book for understanding the brain’s role in love. There are no hard and fast answers. However, there are plenty of interesting surprises to be discovered about our “dirty” minds, both in animal models and in the fMRI scanner. To start I need to provide a little background, a taste of the brain areas and chemicals that fuel this most intoxicating of human emotions. This tale of brains in love begins with a bit of scientific history and the region of the brain responsible for reward processing called the basal ganglia.

Chapter 2

The Ever-Loving Brain

Could anything represent love
better than a big red heart? Probably not. Even outside Valentine’s Day (or rather, the six weeks of frenzied mass marketing that precede it) this particular image is omnipresent. So much so that replacing it with a brain, even now that we know the heart has little to do with emotion, seems just plain wrong. Can you imagine someone giving you a box of candy or an anniversary card shaped like a brain? It doesn’t quite work. The idea is a bit disturbing even to a brain nerd like me.

Why is that one little symbol, a cardiovascular organ that we have now learned is basically just a blood pump, so pervasive? Perhaps it is because for the better part of a thousand years many of the best thinkers believed the heart was not only the seat of emotion, but also the center of rational thought and cognition.

We humans have wanted to differentiate ourselves as logical, reasonable beings since the earliest years of our history and have sought to denote a part of the body responsible for controlling this rationality. Aristotle believed that the heart was the source of human intelligence and vitality due to its heat and movement. (The brain, he believed, was responsible for cooling the passions created by said heart.) Plato, a teacher of Aristotle, disagreed with his student about the center of thought and emotion. He postulated the brain as the rational organ because it was the part inside the body closest to the heavens.

For years philosophers, theologians, and
physicians volleyed back and forth about whether the heart or the brain was the most important organ (with the liver, of all things, occasionally making an appearance in the debate). But without access to scientific methods and the technologies with which to observe how these organs worked within the living body, there could be no definitive answer.
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