The discovery could offer insight into autism and other disorders where social distance is an issue.
The structure, the amygdala - a pair of almond-shaped regions located in the medial temporal lobes - was previously known to process strong negative emotions and is considered the seat of emotion in the brain. However, it had never been linked rigorously to real-life human social interaction.
The scientists, led by Ralph Adolphs, Bren Professor of Psychology and Neuroscience at the California Institute of Technology and postdoctoral scholar Daniel P. Kennedy, were able to make this link with the help of a unique patient, a 42-year-old woman known as SM, who has extensive damage to the amygdala on both sides of her brain.
"SM is unique, because she is one of only a handful of individuals in the world with such a clear bilateral lesion of the amygdala, which gives us an opportunity to study the role of the amygdala in humans," says Kennedy.
The experiment shows that SM's preferred distance was just 34 centimeters whereas the average preferred distance was 64 centimeters.
"Respecting someone's space is a critical aspect of human social interaction, and something we do automatically and effortlessly," Kennedy says. "These findings suggest that the amygdala, because it is necessary for the strong feelings of discomfort that help to repel people from one another, plays a central role in this process. They also help to expand our understanding of the role of the amygdala in real-world social interactions."
Adolphs and colleagues then used a functional magnetic resonance imaging (fMRI) scanner to examine the activation of the amygdala in a separate group of healthy subjects who were told when an experimenter was either in close proximity or far away from them. When in the fMRI scanner, subjects could not see, feel, or hear the experimenter; nevertheless, their amygdalae lit up when they believed the experimenter to be close by.
MEDICA.de; Source: California Institute of Technology