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Love on the Brain

Scientists peeking inside our brains and psyches have more clues than ever about the biology of love -- why we're attracted, why we fall so hard, and what makes us stay.

The Biology of Love: Your Brain in Love continued...

The three brain systems, however, don't always come into play in any kind of order. They can kick in separately of be intertwined. Or they can trigger each other. For instance: you can have sex with someone but not fall in love, of course; you can be in love with someone with whom you've never had sex.

"Of these three systems, in many respects I think the most powerful one is intense romantic love," Fisher says. With Aron and others, Fisher has used functional magnetic resonance imaging (fMRIs) to examine the brains of people in love and get clues about romantic love.

In one study, 17 people who were newly in love and asked to look at a photo of their beloved showed intense activity in two brain regions associated with reward and motivation -- called the ventral tegmental area and the right caudate nucleus. The findings led Fisher's team to suggest that the crazy-in-love feeling is more a motivation system than an emotion. The report was published in 2005 in The Journal of Comparative Neurology.

"Both the VTA and the caudate nucleus are part of the brain reward system," Fisher says. And the VTA, she says, is a "mother lode" for cells that make dopamine, a brain chemical important for controlling emotional response and the ability to feel pleasure and pain. As dopamine levels in the madly-in-love increase, she says, it accounts for focused attention on the new partner, motivation to get the reward -- and the lover's high.

In this romantic love phase, Fisher says, lovers are motivated to win each other over. Obsessive thinking is part and parcel.

"What we are seeing is activation in the same area as when you expect to receive a large reward," Aron says. It's the same area that "lights up" in cocaine users, he says, as they anticipate using the drug.

"What we think is what's going on when one falls in love is, one perceives incredible opportunities for one's life to be enriched," Aron says. "Perhaps the most important reward for most people is falling in love."

The Biology of Love: Smell Counts

Aside from biology and brain activity, body odor is important and help may dictate who we are attracted to and our romantic behavior. "It may be one of the first things that inspires us to say yes or no," says Charles Wysocki, PhD, a researcher at Monell Chemical Senses Center in Philadelphia.

Preference for human body odors is influenced by both gender and sexual orientation, Wysocki and his colleagues found in their research, published in 2005 in Psychological Science. When his study participants of different orientations and genders were asked to choose between distinct odors -- straight men, gay men, straight women, lesbian women -- each picked the odor of a partner of the preferred gender and orientation.

''A person's body odor is determined by a number of factors," Wysocki says," and among them is a set of genes that regulate the immune system." This cluster of genes is called the major histocompatibility complex or MHC. "This MHC confers on an individual an odor print," says Wysocki, citing others' research. And experts have found that a person will seek out a partner with an MHC different than his or her own. "MHC is so variable, no two are alike," Wysocki says.

Next Article:

What physical changes do you experience when in love?