Structure deep within the brain may contribute to a rich, varied social life

December 26, 2010

Scientists have discovered that the amygdala, a small almond shaped structure deep within the temporal lobe, is important to a rich and varied social life among humans. The finding was published this week in a new study in Nature Neuroscience and is similar to previous findings in other primate species, which compared the size and complexity of social groups across those species.

"We know that primates who live in larger have a larger amygdala, even when controlling for overall size and body size," says Lisa Feldman Barrett, PhD, of the Massachusetts General Hospital (MGH) Psychiatric Neuroimaging Research Program and a Distinguished Professor of Psychology at Northeastern University, who led the study. "We considered a single primate species, humans, and found that the amygdala volume positively correlated with the size and complexity of social networks in adult humans."

The researchers also performed an exploratory analysis of all the subcortical structures within the brain and found no compelling evidence of a similar relationship between any other subcortical structure and the social life of humans. The volume of the amygdala was not related to other social variables in the life of humans such as life support or social satisfaction.

"This link between amygdala size and social network size and complexity was observed for both older and younger individuals and for both men and women," says Bradford C. Dickerson, MD, of the MGH Department of Neurology and the Martinos Center for Biomedical Research. "This link was specific to the amygdala, because social network size and complexity were not associated with the size of other brain structures." Dickerson is an associate professor of Neurology at Harvard Medical School, and co-led the study with Dr. Barrett.

The researchers asked 58 participants to report information about the size and the complexity of their social networks by completing standard questionnaires that measured the total number of regular social contacts that each participant maintained, as well the number of different groups to which these contacts belonged. Participants, ranging in age from 19 to 83 years, also received a magnetic resonance imaging brain scan to gather information about the structure of various brain structures, including the volume of the amygdala.

A member of the the Martinos Center at MGH, Barrett also notes that the results of the study were consistent with the "social brain hypothesis," which suggests that the human amygdala might have evolved partially to deal with an increasingly complex social life. "Further research is in progress to try to understand more about how the and other brain regions are involved in social behavior in humans," she says. "We and other researchers are also trying to understand how abnormalities in these brain regions may impair social behavior in neurologic and psychiatric disorders."

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3 / 5 (2) Dec 26, 2010
From wikipedia:

"Shown in research to perform a primary role in the processing and memory of emotional reactions, the amygdalae are considered part of the limbic system.[3]"

This leads me to conclude that selfish persons have smaller Amygdala.

This in turn would seem to indicate that the Amygdala may be that extra something that makes a person more conscience, emotive and considerate.

Does the amygdala determine the size of the social groups or is it the byproduct of such (genetic vs environmental)?

Understanding the amygdala may greatly improve prediction of human behavior.

With the power of cheap/fast gene analysis and a bunch of criminals - one could perform breakthrough psychological research.

The day will come.
5 / 5 (2) Dec 27, 2010
So what you're say is that the problem with the Grinch was the size of his amygdala and not his heart?
1 / 5 (4) Dec 27, 2010
So they've found a correlation beteween the volume[size] of the amygdala and the social network. One obvious conclusion one might want to investigate is whether the size increases as the social network increases - much like the size of one's muscles when exercising them with weights. It's possible that the volume of the amygdala increases because the person experiences a greater variety and volume of emotions and the amygdala needs to increase in size to cope with the increase in chemical activity.
As far as the evolutionary "social brain hypothesis," is concerned - it's a lot of hot air since it cannot be shown that the amygdala was or wasn't there to start off with. In fact it would be very difficult to have any interaction whatsoever if it wasn't - so how would the human beings get along?
not rated yet Dec 27, 2010
Perhaps those with a larger amygdala tend to exaggerate the size of their social networks when filling out surveys.
1 / 5 (2) Dec 27, 2010
"rich and varied social life "
How is this defined?
5 / 5 (1) Dec 28, 2010
kevinrtrs - it would be hard to show any evolutionary theory to a creationist like yourself...
5 / 5 (1) Dec 30, 2010
What will be interesting is to see exactly how changes in social network influence it. I can easily see the amygdala getting bigger as a social network becomes more complex - so it follows that if a social network were to lose complexity and size, the amygdala would shrink. But how quickly? And how drastically? How rapidly can changes be accomodated?
The ability of humans to adapt is ridiculous. Our brains seem to be able to change to respond to whatever we need them to - learning a new language, working around an injury, or whatever we need. Technology's got nothing on the brain!
Jan 01, 2011
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