1 June 2005
Love - Just A Basic Mammalian Response
by Kate Melville

A team led by a neuroscientist, an anthropologist and a social psychologist has found that early, intense romantic love may have more to do with motivation, reward and the "drive" aspects of human behavior than with the emotions or sex drive. The study, using a magnetic resonance imaging (fMRI ) machine, looked at the brain systems of 17 young men and women who described themselves as being madly in love. The researchers found that the parts of the brain that were activated were those that humans share with many other mammals. This led the researchers to theorize that "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."

The study, appearing in the Journal of Neurophysiology, support the two major predictions made by the researchers. That early stage, intense romantic love is associated with subcortical reward regions rich with dopamine; and that romantic love engages brain systems associated with motivation to acquire a reward. "Most of the participants in our study clearly showed emotional responses," noted researcher Arthur Aron of the State University of New York, "but we found no consistent emotional pattern. Instead, all of our subjects showed activity in reward and motivation regions. It's the first physiological data to confirm a connection between romantic love and motivation networks in the brain." Aron also noted that the research answered the question of whether romantic passion is just warmed over sexual arousal. "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."

Researcher Lucy L. Brown, of the Albert Einstein College of Medicine, said the research shows that the right ventral tegmental area (VTA) and dorsal caudate body areas of the brain - which are associated with the motivation to win rewards - are central to the experience of being in love. "Our research helps to explain why a person in love feels 'driven' to win their beloved, amidst a whole constellation of other feelings. The caudate probably integrates huge amounts of information, everything from early personal memories to one's personal notions of beauty. These findings about the diverse regional functions of the basal ganglia in humans have remarkable implications. Our data even may be relevant to some forms of autism. 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," she said.

Research anthropologist Helen E. Fisher, at Rutgers University, noted that not only did the brain change as romantic love endured, but that some of these changes were in regions associated with pair-bonding in prairie voles. 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. 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." Fisher hypothesized, "even love-at-first-sight is a basic mammalian response that developed in other animals and our ancestors inherited in order to speed up the mating process."

The researchers concluded that romantic love does not use a functionally specialized brain system, but rather a combination of neural systems that converge onto widespread regions of the caudate, where there is a flexible combinatorial map integrating many motivating stimuli.

Source: Media release - The American Physiological Society