The Sexual Male, part three: Sex on the Brain

nyone who has seen a friend afflicted with this thing called love can attest to the extreme discomfort it unleashes, not because the friend becomes so unbear­ably fragile but because at any moment you could be ' next. Even if you know better—that it's a chemical reaction, that she's not perfect, that the relationship will probably end badly—love is powerful enough to quickly turn a man from solid to liquid. With rare exceptions, every human falls victim, from high school to nursing home and across races and social classes. Hitler made googly eyes; Einstein went soft in the knees. Love doesn't care if you're already seeing someone. It doesn't wait until the time is right. Scientists suggest that these sudden, intense attachments are nature's way of drugging us; otherwise we would never be so stupid as to reproduce and spend our most productive, energetic years chasing, feeding and socializing ungrateful half cit­izens. Even primitive man had better things to do. As anthropolo­gist Donald Symons notes, the more powerful a feeling has evolved to be, the more difficult the goal it must be trying to achieve.

BRain in Loue The highest compliment you can offer Helen Fisher is to say she seems easy to fall in love with. For the past 25 years, first at the

American Museum of Natural History and now at the Center for Human Evolutionary Studies at Rutgers University, she has exam­ined the mysterious forces that draw couples together. Fisher has come to believe romantic love is a fundamental drive on a par with hunger and thirst, impossible to ignore. It even holds sway over our natural narcissism: A reliable sign that a person has fallen hard is when he says he is willing to die for his lover. "Romantic love is a drug as powerful as any narcotic, if not more so," Fisher says from her Manhattan office near the human zoo of Central Park. "It's thrilling when our love is returned and power­fully negative when it is cut off."

In Fisher's view, the human mating pattern involves three distinct neural processes that developed millions of years ago in our earliest hominid ancestors. In her book Why We Love she identifies them as (a) lust, or the craving for sexual gratification that initiates a pairing ("What a fox!"), (b) attraction, which saves time and energy by helping us focus on suitable partners ("She's the one") and (c) attachment, a.k.a. companionate love, the emotional bond that keeps a couple together at least until their offspring can walk and feed themselves ("We are family"). When you fall for someone, several predictable events occur. First, your beloved takes her place at the center of your existence at the

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expense of friends, family and work (or, as Romeo puts it, "Juliet is the sun"). Second, you aggrandize her as being close to perfect and think about her constantly (or, as Robert Graves puts it, "Love is a bright stain on the vision/Blotting out reason"). Finally, you crave a deep emotional union, a mingling of souls (or, as Modern

English puts it, "I'll stop the world and melt with you").

With the help of a technol­ogy called functional mag­netic resonance imaging, or fMRI, scientists have been able for the first time to peer inside love-pickled brains for clues about how the circuitry works. For a study published in 2005, Fisher, psychologist Arthur Aron and neurologist Lucy Brown recruited 17 men and women ages 18 to 26 who had fallen in love during the previous 17 months. They placed each volunteer's head inside an fMRI scanner, which measures the brain's neural activity by charting blood flow, then displayed a photo of his or her beloved for 30 seconds and watched the fireworks. After analyzing 144 scans of each subject's brain, the team was surprised to see that the region that controls emotions did not light up. Instead the activity was deeper, in the caudate nucleus, part of our subconscious, reptilian core. The nucleus, which Fisher calls "the furnace of roman­tic love," helps us iden­tify, choose and anticipate rewards. This means it goes haywire not only in lovers but in gamblers and cocaine addicts expecting a payday. It showed the most activity in volunteers who scored highest on psychological tests mea­suring their passion (e.g., "I tremble in anticipation at the sight of my lover")—finally, then, we have located the source of all mushy poetry.

The caudate nucleus oper­ates on a circuit with another central part of the brain, the right ventral tegmental area. The VTA is loaded with nerve cells that produce and dis­tribute dopamine, a.k.a. Love Potion No. 1. This neural nar­cotic is responsible for feelings of energy, exhilaration, focus and motivation to pursue—all characteristics of a person in the eriD. Novel exDeriences

appear to drive up dopamine levels; researchers have found people are more receptive to romance after coming off a roller coaster or walking over a narrow, wobbly bridge—two great places, apparently, to meet women. Dopamine also appears to elevate levels of tes­tosterone, which can boost the sex (continued on page 127)

sexuaL maLe

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drive. An Italian neuroscientist, IJr. Donatella Marazziti, has documented other changes, such as the fact that in new lovers, the calming neurotransmitter serotonin drops to a level comparable to that in people who suffer from obsessive-compulsive disorder. More recently, Marazziti reported that 12 newly smitten men had lower levels of testosterone than a control group, while 12 newly smitten women had higher levels. Could it be, she asked, that nature brings us together by temporarily making men more like women and women more like men?

Whatever its methods, nature intends only for you to breed; anything else you accomplish is gravy. To prevent you from coming to your senses after you have fallen for someone, the brain shuts down areas that process negative emo­tions, social judgment and "mentalizing," or assessing other people's intentions and emotions. Love is blind—and also deaf, mute and retarded. You are juiced to a point at which you cannot rationally assess your lover's faults, which forces your friends and family to do it for you. The same chemical changes take place in the mind of another person whose par­ticipation is essential to the perpetuation of the species: a new mother.

Some people so crave the dopamine rush of new love that they date anyone who will have them, jumping from one relationship to the next. Dr. .Michael Liebowitz, author of The Chemistry of Love, has identified these types as "attraction junkies." He and a col­league found that some patients began to choose partners more carefully and feel more at ease being single after receiving antidepressants that boost the level of the brain neurotransmitter phenylethylamine. At the other extreme are people who claim never to have felt lust and/or attrac­tion. Although a true asexual has never been identified, scientists have found the rare male ram, rat or gerbil that shows no interest in mating, and one percent of the respondents in a survey of 18,000 adults claimed never to have felt sexual desire. Fisher believes there are people who form deep attachments but never fall in love. "I've met three people, including, most recently, a 76-year-old man, who did not experience the swirling, craving obsession of romantic love until late in life," she says. In recent years asexuals (a loosely defined group; some people say they feel lust but not infatuation or vice versa) have orga­nized online, arguing that asexuality, like homosexuality, should not be viewed as a disorder. On the bright side, if there is one, never falling in love prevents a great deal of heartache.

BRain in pain As anyone who has been in a serious rela­tionship knows, no matter how strong your initial feelings about your snuggle bunny.

the day arrives when you sober up. When Marazziti took blood from 16 of her 24 volunteers a year or two after they had reported being madly in love, their hor­mone levels had all returned to normal. The thrill was gone. This is for the best, Fisher says: "Many of us would die of sex­ual exhaustion if romantic love flourished endlessly" Coming down from the high doesn't necessarily mean you are no longer interested, just that your brain is making adjustments for the long haul. It produces less dopamine and more serotonin, replac­ing frenzy with calm. Oxytocin kicks in as a stabilizer. If one or both partners can't sustain their oxytocin level, the relationship sputters, although regular sex may help. "If you have enough orgasms with your part-

ner, you may become more attached to her," suggests Fisher, because climax appears to stimulate production of oxyto-cin and vasopressin, two hormones associ­ated with bonding. In animal studies, oxyto-cin has been found to encourage females to nurture their young and vasopressin to push males to defend the nest.

But as anyone who didn't marry their middle-school girlfriend can tell you, things don't always work out. After examining the brain in love. Fisher and her colleagues repeated their fMRI experiment with volunteers who had recently been dumped. In fact, the day after her boyfriend ended their relationship, Fisher put herself into the machine. "I can't ask others to do it unless I'm

willing," she says. As with her subjects, Kisher found a spike in her brain's dopa-mine activity—the same reaction we have when we first fall in love. When a reward is delayed, the brain churns out more dopamine. This explains why, in a phenomenon Fisher calls "frustration-attraction," adversity and barriers stoke the flames. We become obsessed with winning our lover back, agonize over what went wrong and, encouraged by Hollywood endings, make dramatic and ultimately humiliating appearances at their home or work to declare our love. During this initial protest phase many people become enraged, which may be the brain's way of helping us break away.

Fisher agrees with the assessment that the opposite of love is not hate but indif­ference. "Love and hate have too much in common," she says. "They involve similar focus and obsession."

When we finally give up. we are left in despair. With time, our dopamine levels return to normal, helped along by novel activities, basking in sunlight and exer­cise. But an unfortunate few are unable to shake their depression. Terminally love­sick, they resort to suicide, a stunning act of destruction unique to Homo sapiens.

BRain comes It's easy to imagine a group of neuro-scientists examining the first fMRI machines a decade ago in the same way pornogra-

phers once viewed VCRs: Think what we could do with this! Almost immediately they began rolling supine college students head­first into the middle of the donut-shaped scanners and showing them erotica. Before fMRI, much of what scientists knew about the sexual brain came from studying epilep­tics who had reported an "orgasmic aura" before seizures and patients who for various reasons had electrodes implanted in their brain. In 1964 a physician reported that a patient given control over his electrode pressed the button constantly, saying it made him feel as if he were building up to climax. (He may have been stimulating an area involved in what today is known as per­sistent sexual arousal syndrome.) Three of

the doctor's other patients reported getting erections, and a fourth would bring up sex no matter what topic was being discussed. Lobotomies, lesions, tumors and hemor­rhages have led mild-mannered patients to masturbate openly or feel up the nurses. A 75-year-old became "the man with a thou­sand hands," according to his wife. He declined to have a shunt in his brain repo-sitioned to stem his hypersexualiry.

The fMRI makes it easier to observe the brain in heat but presents its own chal­lenges. At Stanford, hospital officials refused to allow liquids (e.g., ejaculate) inside their expensive machine, so researchers could examine only arousal. Even if you can let volunteers reach climax, they must be able to do so without touching themselves,

because masturba­tion activates the area of the brain that controls motor function and thus muddies the images. So far scientists have located only women who are capable of this, although Alfred Kinsey estimated that three or four males in 5.000 possess the skill as well. Ideally, you would want to scan the brain and genitals at the same moment, to see how they interact, but the current technology can handle only so much excitement.

If you don't know anyone who can climax by fantasy alone, the obvious alternative is to lend a hand. This is the Dutch way. In 2005 Gert Hol-stege, a professor of anatomy and embryology at the University of Gron-ingen, reported the results of a study in which he observed

the brains ol 1 1 men ages 19 to 45 as they received hand jobs from their girl­friends or wives while the men's heads were restrained with adhesive bands inside a positron emission tomography (PET) scanner. He repeated the experi­ment with 13 women. After studying the images, Holstege concluded that while the female brain appears to become lost in the moment during arousal and cli­max, the male brain remains engaged, anticipating the pleasure of being touched. It's hard to underestimate the importance of this aspect of male sexu­ality—studies suggest that a part of the brain known as the claustrum not only assists in creating fantasies but helps us

jump into any erotic scenes we encoun­ter. Even when we aren't being touched, we can easily imagine the sensation.

As a man becomes aroused, the amyg­dalae, two almond-shaped regions of the brain whose duties include keeping him constantly vigilant for hazards and threats, become much less active, just as they do when he is in the throes of new love. Hol-stege believes the do not disturb sign goes up so that the male animal can con­centrate on the task at hand—reproduc­tion—without being distracted by every rustle in the brush. "Apparently a general lack of fear is necessary for ejaculation," he writes. Indeed, one study found that men watching porn showed a diminished starde response to a sudden burst of white noise. The time it took each man to punch the scientist remained constant.

your sexuaL cerueR Although many parts of the brain are involved in sexuality, the circuit board for our carnal desires appears to lie within the dime-size hypothalamus buried deep in the skull. As if processing your insatiable libido weren't enough, it also controls hunger, cardiovascular performance, body tem­perature, stress and emotional responses.

"Imagine the hypothalamus as a row of dip switches," says biologist Simon LeVay. "They seem too tiny to be important but regulate everything." The precise source of the male drive appears to be located front and center, at a cowboy bar called the medial preoptic, where most of the brain neurons having androgen receptors are located. (The apparent center of the female sex drive, the ventromedial nucleus, is a few millimeters away.) When a male mon­key first sees a female in heat and presses a button to move toward her, the neurons in his medial preoptic go berserk. During intercourse the activity declines (no need for it while youVe getting laid), and after ejaculation it falls again (mission accom­plished). When researchers damage the region, male monkeys lose most or all inter­est in females, though they will continue to masturbate. Something similar occurs in humans. In West Germany in the 1960s doctors destroyed the medial preoptics of a number of men whose sexual behavior was thought to be pathological or sociopadiic. As LeVay reports in his book The Sexual Brain, the men experienced a severe loss of desire and had few if any fantasies. Con­versely, when a monkey's medial preoptic is stimulated with electricity, the otherwise

suave simian gets so horny he offers the female only a few seconds of foreplay. The area may also be involved in sexual orienta­tion. In 1995 scientists at Boston University who mucked with it were able to change male ferrets from straight to gay.

If the hypothalamus powers our carnal instincts, the amygdalae add a touch of humanity. Located on eadi side of the brain, these regions process emotional and visual stimuli. They are more than twice the size in humans as in apes, which may explain why we feel such intense emotions. A woman's amygdalae are more easily activated by what has been called emotional nuance, which is what gives your wife the ability even years later to recall vivid, pointless details of your first date. In men the amygdalae appear to be a way station for the male gaze. Although a 2006 study found the cortex of both gen­ders registers erotic scenes 20 percent faster than nonsexual ones (suggesting that some-neurons may be "tuned" for sex), what the male and female brains do with this data is vastly different. When a man sees an image of a couple having sex—or dancing or talk­ing, for that matter—his amygdalae (par­ticularly the left) and hypothalamus show far more activity than a woman's. We are not alone in our appreciation of the female form; male rhesus monkeys, given the choice of juice or a photo of a female mon­key ass, consistently choose the ass. Accord­ing to Stephan Hamann, a neuroscientist at Emory University, the amygdalae appear to control appetitive (desirous or wanting) but not consummatory (copulatory) sexual behaviors. That is, when the amygdalae arc-disabled in a male rat, he will still mount females placed directly beside him but show no desire to pursue. If he must go to the trouble of pushing a lever to have a randy female drop into his cage, forget it.

ST UIILL

While examining the PET scans from his hand-job studies, Holstege, at the University of Groningen, was surprised to see that the hypothalamus, while con­stantly pushing you to procreate, doesn't make a peep when you are actually hav­ing sex—it drives you to the party but doesn't go inside. Thankfully, the hypo­thalamus does call ahead to make sure you have a good time. When you first get turned on, some of its neurons fire oxytocin down the spinal cord to alert other neurons in the pelvis. Oxytocin is a neurohormone, which means it can travel in the central nervous system as well as in the blood, allowing you to get hard that much quicker. (Some research­ers speculate that the more oxytocin deployed, the more intense the orgasm will be.) Once activated, nerves at the base of the spine send signals that relax the involuntary muscles around the tiny arteries in your penis, allowing blood to rush in. The blood presses against the veins running along the outside of the penis, keeping you hard. Other nerves instruct the perineum—the powerful

muscle between your testicles and anus—to contract, pulling your erec­tion to lull mast. When you are suffi­ciently aroused, the brain sends a signal to release the hounds. Il is not clear how the brain knows the time has come for climax; suggestions that semen volume or pressure is the trigger have been largely discounted.

The nature of the brain-penis rela­tionship can most easily be seen in men who have suffered spinal-cord injuries. Many paralyzed men are able to get hard and come, but they feel no plea­sure. The nerves at the base of the spine that control erection and ejaculation can still communicate with the penis but not the brain, so any erections that occur are simply reflexes. However, as researchers have only recently dis­covered, there may be a bypass to the spinal cord's sensory highway. By 1990 scientists had established that a pair of primitive nerves known as the vagus ("wandering"), which meanders from the base of the brain and around the heart, lungs, stomach, liver and intes­tines and regulates vital functions such as breathing and swallowing, reaches past the abdomen into the pelvis. Then, in 2004, Beverly Whipple and Barry Komisaruk of Rutgers announced they had documented sexual impulses being sent along the route. They had placed women paralyzed from the waist down into an fMRI and asked them to mastur­bate even though they couldn't feel their fingers on their clits. "One woman with a completely severed spinal cord had six orgasms," recalls Whipple, whose most recent book is The Science a] Orgasm, written with Komisaruk and biologist Carlos Beyer-Flores. "Our scans found her brain was reacting to (he stimulation in the same way as people who aren't paralyzed. How do you explain this? Imagery lights up a different part of (he brain, so she wasn't imagining it." After injecting the woman with a tracer, Whipple and Komisaruk followed the impulses along the vagus. Komisaruk hopes to begin a similar experiment with men next year. He suspects the vagus connects the brain to the prostate, meaning volunteers should be able to climax by stimulating the gland.

The ability of some women and per­haps some men to get sexual pleasure from the rhythmic stimulation of an area just above the level of their injury, e.g., the chest, shoulder or chin, reveals us to be total erotic beings. Although it's far easier to climax by stroking the genitals, caressing any part of the body apparently can "recruit" neurons in the brain to become more and more active, until, as with a sneeze or a yawn, there is a sudden release of tension—a gasp, perhaps, then calm. For the moment, everything is right with the world.