How friends matter to your brain

http://thechart.blogs.cnn.com/2010/10/12/how-friends-matter-to-your-brain/

Your friends may matter to you in ways that you can't even see - at the level of neural circuitry in the brain.

It turns out that the brain's frontal midline, an area between the two hemispheres that is associated with socialization and the way you think about yourself, also shows a greater response from friends than strangers, even strangers with similar interests and lifestyles, said Fenna Krienen, graduate student at Harvard University and lead author of a new study on the subject.

"What we ended up finding is that closeness really seems to matter to these circuits in the brain much more than similarity," she said.

Krienen's study, published in the Journal of Neuroscience, did four different functional magnetic imaging experiments on a total of 98 participants to explore these issues of brain activation and social ties.

They looked at how the brain would respond to strangers who have different interests from those of the participants, compared  with strangers with common interests, and whether that reaction would correspond to what they observed with friends.

Some participants viewed photos that they brought in of two friends and answered questions that mimicked the TV show “The Newlywed Game," which dealt with how their friends would answer particular questions. One of these friends was someone the individual participant considered similar to himself or herself; the other the participant viewed as dissimilar. They also did this with "strangers" - researchers had invented their biographies, and paired photos with them that previous participants had brought in of their friends. Some of these biographies indicated similar interests to those of the participants, others were different.

Researchers found that it didn't matter whether the strangers had common or dissimilar interests to their own - the strangers tended not to produce the same effect on the medial prefrontal regions and associated regions as the friends. It also didn't matter whether participants considered the friends similar or unlike themselves; the relevant brain regions showed enhanced responses to both kinds of friends.

"In every case, it seemed like friends were processed with much greater neural activity in brain networks that make sense to us than did strangers," Krienen said.

More precisely, the scientists saw increased blood oxygenation levels in the frontal midline and associated regions. This indicates increased neuronal activity in those areas.

This brain area, in addition to social responses, has been shown in other research to be involved in tasks that require calculating expected rewards and making other kinds of decisions.

Previous research had also looked at these regions on the question about how the brain responds to strangers, but this is a first look at how the similarity of acquaintances and strangers might play a role, Krienen said. The study proposes further research in this area, including a study of how the brain responds to a close acquaintance with whom the participant doesn't get along very well.