Biology: Your Brain In Love

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Many brain parts became active in our love-struck subjects when they focused on their beloved. However, two regions appear to be central to the experience of being in love. Perhaps our most important finding concerned activity in the caudate nucleus. This is a large, C-shaped region that sits deep near the center of your brain. It is very primitive--part of what is called the reptilian brain because it evolved long before mammals proliferated, some 65 million years ago. Our brain scans showed that parts of the body and the tail of the caudate became particularly active as a lover gazed at the photo of a sweetheart.

I was astonished. Scientists have long known that this brain region directs bodily movement. Only recently have they come to realize that it is also a key part of the brain's "reward system," the mind's network for general arousal, sensations of pleasure and the motivation to acquire rewards. Not only did our subjects exhibit activity in the caudate, but also the more passionate they were, the more active their caudate was.

We discovered this in a curious way. Before our subjects entered the brain scanner, we asked each to fill out several questionnaires, including a survey designed by psychologist Elaine Hatfield and sociologist Susan Sprecher called the Passionate Love Scale (see box). We wanted to compare the brain activity of each subject to what that subject reported on a questionnaire. We found a positive correlation: those who scored higher on the Passionate Love Scale also showed more activity in a specific region of the caudate.

We also found activity in other regions of the reward system, including areas of the septum and a brain region that becomes active when people eat chocolate. Chocolate can be addictive. I maintain that romantic love is addictive too.

--THE DOPAMINE MOTHER LODE

Another striking result from our FMRI experiment concerned activity in the ventral tegmental area (VTA), a central part of the reward circuitry of the brain. This result was what I was looking for. As you know, I had hypothesized that romantic love is associated with elevated levels of dopamine or norepinephrine. The VTA is a mother lode for dopamine-making cells. With their tentacle-like axons, these nerve cells distribute dopamine to many brain regions, including the caudate nucleus. And as this sprinkler system sends dopamine to various parts of the brain, it produces focused attention as well as fierce energy, concentrated motivation to attain a reward, and feelings of elation--even mania--the core feelings of romantic love.

No wonder lovers talk all night or walk till dawn, write extravagant poetry and self-revealing e-mails, cross continents or oceans to hug for just a weekend, change jobs or lifestyles, even die for one another. Drenched in chemicals that bestow focus, stamina and vigor, and driven by the motivating engine of the brain, lovers succumb to a Herculean courting urge.

--THE DRIVE TO LOVE