The early stages of a romantic relationship spark activity in dopamine-rich brain regions associated with motivation and reward. The more intense the relationship is, the greater the activity.

The regions associated with emotion, such as the insular cortex and parts of the anterior cingulate cortex, are not activated until the more mature phases of a relationship, says Helen Fisher, an anthropologist from Rutgers University in New Jersey.

Fisher and colleagues recruited seven male and 10 female volunteers who claimed to be madly in love. They asked them to look at pictures of either their loved one or another familiar person while inside a functional MRI scanner.

Eating chocolate
 

Early on in a relationship, the images showed that the brain seems to be very focused on planning and pursuit of pleasurable reward, says Fisher, mediated by regions called the right caudate nucleus and right ventral tegmentum. The same regions become active when a person enjoys the pleasure of eating chocolate, she adds.

There are also patterns that resemble aspects of obsessive compulsive disorder. "Activity in one particular area of the anterior cingulate cortex is in common," says Lucy Brown, a neuroscientist from Albert Einstein College of Medicine in New York, who was part of the research team. "The activity is correlated with the length of a relationship, lasting just into the emotional stage."

There are some differences between love-struck men and women, says Fisher. Women in love show more emotional activity earlier on in a relationship. They also seem to quiz their memory regions as they look at pictures of their partner, perhaps paying more attention to their past experience with them.

For men, perhaps unsurprisingly, love looks a little more like lust, with extra activity in visual areas that mediate sexual arousal.

The team has since moved on to examining the final phase of romance. "We are now looking at people who have just been rejected," says Fisher. The research was presented at the Society for Neuroscience's meeting in New Orleans on Tuesday.

Helen Phillips, New Orleans