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UI researchers find link between amygdala and social judgment
IOWA CITY, Iowa -- Damage to a brain structure called the amygdala impairs
the ability to judge the trustworthiness of others, researchers in the
University of Iowa College of Medicine report in the June 4 issue of the
Investigators in the UI department of neurology studied patients with
a rare type of damage to the amygdala (a brain region known to be involved
with emotion and social behavior), as well as people with undamaged brains
and people with other types of brain damage. They found that bilateral
damage to the amygdala prevents patients from judging that other people
look unapproachable or untrustworthy. As a result, patients choose to approach
and to trust individuals one might normally avoid.
The study, conducted by Drs. Ralph Adolphs, assistant professor of neurology,
Daniel Tranel, professor of neurology, and Antonio R. Damasio, Van Allen
Professor and head of neurology, builds on previous investigations by the
same researchers. The idea that the amygdala serves to trigger knowledge
and behaviors associated with negative emotions was developed in Damasio's
book "Descartes' Error." The hypothesis has been supported by
numerous studies from several laboratories. Previously, the group discovered
that patients with amygdala damage cannot recognize fear in other people's
"Taken together, all these findings show that emotion and social
behavior depend on specific brain systems in humans as well as in animals,"
Adolphs says. "The amygdala is one critical structure, without which
we cannot recognize certain emotions or judge trustworthiness from other
Adolphs adds that the findings are especially convincing because the
patients have entirely normal vision. "They can see other people's
faces perfectly fine but they are unable to judge, from looking at someone's
face, if the person should be approached or should be trusted."
Damasio and his colleagues already have studies under way, using state-of-the-art
imaging methods, that will further explore how the human brain processes
emotion and social information.
"Over the next few years, it will be possible to identify which
brain systems process different human emotions," Damasio says. "The
new findings will help design novel approaches to disorders of emotion
and mood, and to better understand the social dimension of those disorders."