'Romantic love is probably best characterized as a motivation or goal-oriented state that leads to various specific emotions, such as euphoria or anxiety. With this view, it becomes clearer why the lover expresses such an imperative to pursue his or her beloved and protect the relationship.'

The researchers detected quantifiable love responses in the brains of 17 young men and women who each described themselves as being newly -- and madly -- in love.

The multidisciplinary team found that early, intense romantic love may have more to do with motivation, reward and "drive" aspects of human behavior than with the emotions or sex drive.

Brain systems were activated that humans share with other mammals. So the researchers think "early stage romantic love is possibly a developed form of a mammalian drive to pursue preferred mates, and that it has an important influence on social behaviors that have reproductive and genetic consequences."

What Are You Getting Out of It?

The reward response is primary, the scientists say.

"It's a stark reminder that the mind truly is in the brain," noted Lucy L. Brown of the Albert Einstein College of Medicine.

"We humans are built to experience magical feelings like love, but our findings don't diminish the magic in any way. In fact, for some, it enhances the experience. Our research also helps to explain why a person in love feels 'driven' to win their beloved, amidst a whole constellation of other feelings," Brown added.

The study, entitled "Reward, motivation and emotion systems associated with early stage intense romantic love," is available online and will be in the July issue of the Journal of Neurophysiology, published by the American Physiological Society. The research was conducted by Arthur Aron, Helen E. Fisher, Debra J. Mashek, Greg Strong, Hai-Fang Li and Lucy L. Brown. Aron, Fisher and Brown contributed equally.

"Most of the participants in our study clearly showed emotional responses," noted Arthur Aron of the State University of New York-Stony Brook, "but we found no consistent emotional pattern. Instead, all of our subjects showed activity in reward and motivation regions. To emotion researchers like me, this is pretty exciting, because it's the first physiological data to confirm a connection between romantic love and motivation networks in the brain," he pointed out.

"As it turns out, romantic love is probably best characterized as a motivation or goal-oriented state that leads to various specific emotions, such as euphoria or anxiety," Aron said. "With this view, it becomes clearer why the lover expresses such an imperative to pursue his or her beloved and protect the relationship," he explained.

Sex Plays Supporting Role

"Our participants who measured very high on a self-report questionnaire of romantic love also showed strong activity in a particular brain region -- results that dramatically increase our confidence that self-report questionnaires can actually measure brain activity," Aron added.

The research answered the "historic question of whether love and sex are the same, or different, or whether romantic passion is just warmed over sexual arousal," Aron noted.

"Our findings show that the brain areas activated when someone looks at a photo of their beloved only partially overlap with the brain regions associated with sexual arousal. Sex and romantic love involve quite different brain systems," he said.

Tests Reveal Autism Link

Through functional magnetic resonance imaging (fMRI) and other measurements, the research team found support for two major predictions:

(1) early stage, intense romantic love is associated with subcortical reward regions rich with dopamine; and

(2) romantic love engages brain systems associated with motivation to acquire a reward.

"When our participants looked at a photo of his/her beloved, specific activation occurred in the right ventral tegmental area (VTA) and dorsal caudate body," Brown said.

"These regions were significant compared to two control conditions, providing strong evidence that these brain areas, which are associated with the motivation to win rewards, are central to the experience of being in love," she noted.

"An important concept is that the caudate probably integrates huge amounts of information -- everything from early personal memories to one's personal notions of beauty. Then, this brain region (and related regions of the basal ganglia) helps to direct one's actions toward attaining one's goals. For neuroscientists, these findings about the diverse regional functions of the basal ganglia in humans have remarkable implications," Brown said.

"Our data even may be relevant to some forms of autism," she added. "Some people with autism don't understand or experience any sort of emotional attachment or romantic love. I would speculate that autism involves an atypical development of the midbrain and basal ganglia reward systems. This makes sense, too, because other symptoms of autism include repetitive thoughts and movements -- characteristics of basal ganglia function. "

Right for Romance, Left for Looks

Another important discovery -- to the research team's surprise -- was that "the activation regions associated with intense romantic love were mostly on the right side of the brain, while the activation regions associated with facial attractiveness were mostly on the left," Brown said.

"We didn't predict such a striking lateralization," she remarked.

"It is well known that speech is largely a left-sided cortical function. But our data indicate that lateralization also occurs in lower parts of the brain. Moreover, different kinds of rewards (in this case, the "rush" of romantic love, compared with the pleasing experience of looking at a pretty or handsome face) is also lateralized. These results give us a lot to think about how the normal human brain learns and remembers and functions in general," Brown added.

Power of Romantic Love

Another breakthrough was that "we found several brain areas where the strength of neural activity changed with the length of the romance. Everyone knows that relationships are dynamic over time, but we are beginning to track what happens in the brain as a love relationship matures," Brown noted.

Some of the brain changes as romantic love endured were in regions associated with pair-bonding in prairie voles, according to Helen E. Fisher, a research anthropologist at Rutgers University, New Jersey. The fMRI images showed more activity in the ventral pallidum portion of the basal ganglia in people with longer romantic relationships. It's in this region where receptors for the hormone vasopressin are critical for vole pair-bonding, or attachment.

"Humans have evolved three distinct but interrelated brain systems for mating and reproduction -- the sex drive, romantic love, and attachment to a long term partner," Fisher said, "and our results suggest how feelings of romantic love might change into feelings of attachment. Our results support what people have always assumed: that romantic love is one of the most powerful of all human experiences. It is definitely more powerful than the sex drive."

Depression, Murder/Suicide Connection

"If someone rejects your sexual overtures, you don't harm yourself or the other person," Fisher points out. "But rejected men and women in societies around the world sometimes kill themselves or someone else. In fact, studies indicate that some 40% of people who are rejected in love slip into clinical depression. Our study may also suggest some of the underlying physiology of stalking behavior," she added.

The study -- which took barely an hour for each participant but many years for the researchers to process and interpret the data -- also found a "fascinating continuity between human romantic love and the physiological expressions of attraction in other animals," Fisher noted.

"Other scientists have reported that expressions of attraction in a female prairie vole are associated with a 50% increase in dopamine activity in a brain region related to regions where we found activity. These and other data indicate that all mammals may feel attraction to specific partners, and that some of the same brain systems are involved," she said.

Second Half of Darwin's Puzzle

"Darwin and many of his intellectual descendants have studied the myriad physiological ornaments that one sex of a species have evolved to attract members of the opposite sex -- like the peacock's fancy tail feathers that attract the peahen," Fisher noted.

"But no one has studied what happened in the brain of the viewer -- the individual that becomes attracted to these traits. Our study indicates what happens in the brain of the viewer as he or she becomes physiologically attracted to these traits," she said.

"This brain system probably evolved for an important reason -- to drive our forebears to focus their courtship energy on specific individuals, thereby conserving precious mating time and energy. Perhaps even love-at-first-sight is a basic mammalian response that developed in other animals, and our ancestors inherited [it] in order to speed up the mating process," she hypothesized.

Trick of the Mind

"Our results suggest that romantic love does not use a functionally specialized brain system," Einstein's Brown concluded.

"It may be produced, instead, by a constellation of neural systems that converge onto widespread regions of the caudate where there is a flexible combinatorial map representing and integrating many motivating stimuli," she explained.

"This passion may be an excellent example of how a complex human behavioral state is processed. Moreover," Brown said, "taken together, our results and those of Andreas Bartels and Semir Zeki, who studied men and women in longer love relationships, show similar cortical, VTA and caudate activation patterns, suggesting that these regions are consistently and critically involved in this aspect of human reproduction and social behavior -- romantic love."