Scientists from University College London believe they have identified the parts of the brain responsible for true love. Using a functional magnetic resonance scanner, Andreas Bartels and Semir Zeki monitored the brain activity of 17 volunteers who described themselves as "madly and truly in love." The volunteers, recruited from posters placed around the university, were shown pictures of the partners with whom they claimed to be "head over heels in love" while a scan took place. They were then shown pictures of a friend who was the same sex as their partner and were scanned again. Four areas of the brain which were not active when looking at pictures of a friend became active when the volunteer saw pictures of a partner; pictures of a partner also caused a marked decrease in another area of the brain.

The regions showing activity are deep in the cortex of the brain: the medial insula (which is associated with "gut feelings") and in part of the anterior cinguate, which is known to respond to euphoriainducing drugs. Deeper into the striatum, two other areas, which are active when we find experiences rewarding, were also stimulated by viewing pictures of loved ones. The right prefrontal cortex, a region where activity is heightened in depressed patients, became inactive when the pictures were viewed.

"Our interest was in studying the effect of visual input on emotional states of the brain," said Dr Bartels. "Love has not been studied in terms of brain activation before, while many other emotions have." He continued: "All the differences in brain activity were highly significant. The activity that we report is common to all 17 subjects - individuals will certainly have additional areas activated due to specific associations, which are different for each person."

The researchers used lie detectors to verify the feelings of the 11 women and six men taking part in the study before the scans were performed. There appeared to be no significant differences in brain activity between the two sexes, although more testing may have to take place to validate this. The study was presented to the bi-yearly meeting of the Federation of European Neuroscience Societies in Brighton at the end of June.

Whether the study will result in any commercial application remains to be seen. "I'm convinced that we can use it as a test for love - however, it's rather an expensive one!" says Dr Bartels. If love as an emotion is a specific type of brain activity, however, and a drug can be made to induce that activity, love may go from being blind to being eminently bankable.