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Social Network Size Associated With Brain Structure

Three sites show increased gray matter density with increased online social network size

THURSDAY, Oct. 20 (HealthDay News) -- The size of a person's online social network is associated with the gray matter density of specific regions in the brain, and these regions are specific to Web-based networks rather than real-world social networks, according to a study published online Oct. 19 in the Proceedings of the Royal Society B.

Ryota Kanai, Ph.D., from University College London, and colleagues analyzed brain regions associated with an individual's online social network size. Structural magnetic resonance imaging (MRI) scans were evaluated from 125 healthly adult volunteers and a replication sample of 40 volunteers. Voxel-based morphology was used to compute regional gray matter volume across the whole brain based on T1-weighted anatomical MRI scans. The number of friends each individual had in their Facebook public profile was recorded. In addition, the number of Facebook friends was correlated with real-world social network sizes.

The investigators found that the number of friends an individual declares on a Web-based social network predicted gray matter density in the right superior temporal sulcus, left middle temporal gyrus, and entorhinal cortex. There was a significant correlation between the variability in the size of Web-based social networks with the size of real-world social groups. Gray matter density of the right superior temporal sulcus, left middle temporal gyrus, and entorhinal cortex was only associated with Web-based social network size. Gray matter density of the amygdala was associated with Web-based and real-world social network sizes.

"The size of an individual's online social network is closely linked to focal brain structure implicated in social cognition," the authors write.

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