14 DAY TRIAL // It seems that the larger the amygdala is in people, the wider their social network seems to be, according to a team of US researchers.
The amygdala is a small almond shaped structure within the temporal lobe, that seems to regulate the social life in primates (according to previous research), humans included.
To verify this theory, the researchers asked 58 participants to give information about size and the complexity of their social networks by filling out standard questionnaires measuring the overall number of regular social contacts that each participant maintained, as well the number of different groups to which these contacts belonged.
Participants, were aged from 19 to 83 years, and they underwent a magnetic resonance imaging brain scan to gather information about the structure of several brain structures, including the size of the amygdala.
Lisa Feldman Barrett, PhD, of the Massachusetts General Hospital (MGH) Psychiatric Neuroimaging Research Program and a Distinguished Professor of Psychology at Northeastern University, leader of the study, said that “we know that primates who live in larger social groups have a larger amygdala, even when controlling for overall brain size and body size.
“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 scientists carried out exploratory analysis of all the subcortical structures within the brain and they concluded that there was not enough evidence that a similar relationship existed between the humans' social life and any other subcortical structure.
In other words, the volume of the amygdala has no connection with people's life support or social satisfaction.
Bradford C. Dickerson, MD, of the MGH Department of Neurology and the Martinos Center for Biomedical Research, associate professor of Neurology at Harvard Medical School, and co-leader of the study said that “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.
“This link was specific to the amygdala, because social network size and complexity were not associated with the size of other brain structures.”
Barrett, who is also a member of the the Martinos Center at MGH, added that the study results confirm the 'social brain hypothesis' – the human amygdala could have evolved to also deal with a more complex social life.
She says that “further research is in progress to try to understand more about how the amygdala and other brain regions are involved in social behavior in humans.
“We and other researchers are also trying to understand how abnormalities in these brain regions may impair social behavior in neurologic and psychiatric disorders.”
The conclusions were published this week in a new study in Nature Neuroscience.