How the Brain Encodes Social Network Structure

Summary: Brain regions associated with spatial processing also appear to govern and encode information about social relationships.

Source: SfN

The brain encodes information about our relationships and the relationships between our friends using areas involved in spatial processing, according to new research published in Journal of Neuroscience.

Humans maintain hundreds of social relationships, requiring the brain to catalogue countless details about each person and their connections to other people. But it is not known how exactly the brain stores all of this information.

To uncover how the brain encodes social network structure, Peer et al. used Facebook data to map out participants’ social connections. Then the researchers measured their brain activity with fMRI as they thought about people from their network.

Thinking about a connection generated a unique activity pattern in the retrosplenial complex, a brain region involved in processing spatial information.

This shows brain scans from the study
Along the medial wall, activity pattern similarity in the medial parietal lobe represented information on the social network distance between individuals and their personal affiliation to the participant, while pattern similarity in the medial prefrontal cortex was correlated to similarity between individuals in their perceived personality traits. Credit: Peer et al., JNeurosci 2021

The “distance” between two people in the social network was reflected by the similarity between the activity patterns. Closer people — indicated by number of mutual friends — had similar activity patterns, while more distant people had dissimilar patterns.

Information about each connection’s personality was encoded in the medial prefrontal cortex; people with similar personalities elicited similar activity patterns.

These results indicate the brain separates different aspects of social knowledge into unique representations.

About this neuroscience research news

Source: SfN
Contact: Calli McMurray – SfN
Image: The image is credited to Peer et al., JNeurosci 2021

Original Research: Closed access.
Brain coding of social network structure” by Michael Peer, Mordechai Hayman, Bar Tamir and Shahar Arzy. Journal of Neuroscience


Brain coding of social network structure

Humans have large social networks, with hundreds of interacting individuals. How does the brain represent the complex connectivity structure of these networks? Here we used social media (Facebook) data to objectively map participants’ real-life social networks.

We then used representational similarity analysis (RSA) of fMRI activity patterns to investigate the neural coding of these social networks as participants reflected on each individual. We found coding of social network distances in the default-mode network (medial prefrontal, medial parietal and lateral parietal cortices).

When using partial correlation RSA to control for other factors that can be correlated to social distance (personal affiliation, personality traits and visual appearance, as subjectively rated by the participants), we found that social network distance information was uniquely coded in the retrosplenial complex, a region involved in spatial processing. In contrast, information on individuals’ personal affiliation to the participants and personality traits was found in the medial parietal and prefrontal cortices, respectively.

These findings demonstrate a cortical division between representations of non-self-referenced (allocentric) social network structure, self-referenced (egocentric) social distance and trait-based social knowledge.

Significance statement

Each of us has a social network composed of hundreds of individuals, with different characteristics and different relations between them.

How does our brain represent this complexity? To find out, we mapped participants’ social connections using FacebookTM data, and then asked them to think about individuals from their network while undergoing functional MRI scanning.

We found that the position of individuals within the social network, as well as their affiliation to the participant, are mapped in the retrosplenial complex – a region involved in spatial processing. Individuals’ personality traits were coded in another region, the medial prefrontal cortex.

Our findings demonstrate a neural dissociation between different aspects of social knowledge, and suggest a link between spatial and social cognitive mapping.

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