For centuries, love has been probed -- and of course celebrated -- mostly by poets, artists and balladeers. But now its mysteries are yielding to the tools of science, including modern brain-scanning machines.
At State University of New York at Stony Brook, a handful of young people who had just fallen madly in love volunteered to have their brains scanned to see what areas were active when they looked at pictures of their sweethearts. The brain areas that lighted up were precisely those known to be rich in a powerful "feel-good" chemical, dopamine, which brain cells release in response to cocaine and nicotine. Dopamine is the key chemical in the brain's reward system, a network of cells that is associated with pleasure -- and addiction.
In the same lab, older volunteers who said they were still intensely in love after two decades of marriage participated in the experiment as well. The same brain areas lighted up, showing that, at least in some lucky couples, the honeymoon feeling can last. But in these folks, other areas lighted up too -- those rich in oxytocin, the "cuddling" chemical that helps new mothers make milk and bond with their babies, that is secreted by both sexes during orgasm and that, in animals, has been linked to monogamy and long-term attachment.
It's way too soon (and, we can hope, always will be) to say that brain scientists have translated all those warm and fuzzy feelings we call romantic love into a bunch of chemicals and electrical signals in the brain.
But they do have a plausible hypothesis -- that dopamine plays a big role in the excitement of love and that oxytocin is key for the calmer experience of attachment. Granted, the data are preliminary. But the findings so far are provocative. And it's conceivable that, as Emory University neurobiologist Larry J. Young pointed out in the journal Nature this year, once scientists understand the chemistry of love, drugs to manipulate the process "may not be far away."
A new study published this year in Biological Psychiatry supports that idea, showing that oxytocin may help human couples get along better. Swiss researchers gave 47 couples a nasal spray containing either oxytocin or a placebo. The couples then participated in a videotaped "conflict" discussion. Those that got oxytocin exhibited more positive and less negative behavior than those given the placebo. Oxytocin was also linked to lower secretion of cortisol, a stress hormone.
In the Nature paper, Emory's Young also noted that nobody knows yet whether drugs used to treat problems such as depression and sexual dysfunction can affect relationships by changing brain chemistry. But, he noted, both the antidepressant Prozac and the erection enhancer Viagra appear to affect the oxytocin system.
In the initial love study at Stony Brook, 10 women and seven men in intense, "early-stage" love were put into a functional MRI brain scanner, which can detect activity in specific parts of the brain. They were then shown pictures of their loved one or a neutral person.
In these lovebirds, one dopamine-rich region in particular -- the ventral tegmental area -- consistently lighted up upon viewing the loved one, but not the neutral person, according to the research, published in 2005. The intensity of the brain's response to falling in love, says co-author Lucy L. Brown, a neuroscientist at Albert Einstein College of Medicine, suggests that it "is not just an emotion but a drive, a real goal like food or water."
In a second experiment, the team found the same brain areas at work in people recently rejected by a loved one. Perhaps loss of love triggers the same kind of craving as withdrawal from cocaine or cigarettes, suggests Helen Fisher, a biological anthropologist at Rutgers University who also worked on the study.
In new data presented at scientific meetings in 2008 and 2009, Bianca Acevedo, now a post-doctoral fellow in social neuroscience at UC Santa Barbara but formerly at Stony Brook, focused on 10 women and seven men still in love after 21 years of marriage. Like the young lovers, when these volunteers were put in scanners and shown pictures of their partners, their dopamine-rich areas lighted up.
"But in contrast to those newly in love," Acevedo says, other brain regions did too, including areas rich in oxytocin, vasopressin (a similar chemical) and serotonin, a brain chemical associated with well-being and calmness.
The link between long-term attachment and oxytocin has long fascinated researchers, among them, Sue Carter, a neuroendocrinologist at the University of Illinois at Chicago.
Carter's work has centered on prairie voles, known for their enduring bonds. Compared with other rodents, prairie voles -- part of the only 3% of mammals that form monogamous bonds -- have more active oxytocin. Moreover, brain cells with receptors that specifically latch onto oxytocin lie in the very brain regions believed to be important in forming attachments, Carter says.
Other researchers have shown that when mice (not known for their monogamous ways), are injected with a gene containing instructions for making the receptor of oxytocin, the mice cozy up to their mates like voles.
Lack of oxytocin is important too. For instance, if female animals are stressed by being isolated, their oxytocin drops. In humans, Emory University research shows that women who were seriously abused as children have low oxytocin levels as adults.
One question emerging from all this is whether knowing the chemistry of love can help in picking a compatible partner in the first place.
Fisher, the Rutgers anthropologist, who consults for the dating websites Match.com and an affiliate, Chemistry.com, thinks so. She thinks that certain personality types correspond to the preponderance and ratios of specific chemicals in the body; her team is examining blood, urine and saliva samples to test her theory.
Creative, risk-taking personalities, which she calls "explorers," may have more active dopamine systems, as well as more activity of another brain chemical, norepinephrine, she says. In a study that involved 28,000 people using Chemistry.com Fisher built personality profiles based on people's answers to a long questionnaire. She sorted people into different types and then followed their dating experience to see which types were attracted to which other types.
She found that explorers are particularly drawn to other explorers." People she calls "builders," conventional, calm, conscientious folks, may have more active serotonin and may also be drawn to other builders.
By contrast, Hillary Clinton types -- "directors" -- who are analytical and tough-minded may be high in testosterone and are regularly drawn to their opposites, the "negotiators" like Bill Clinton, who may be fueled by estrogen and oxytocin, Fisher says.
Whether this love chemistry will pan out in the new research is still an open question. In the meantime, remember those prairie voles -- they get what Fisher calls "life's greatest prize -- an enduring mate and partner."
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