Through faces to (social) cognition

Studying the connectivity of face processing areas in monkeys reveals the routes by which information about faces is exchanged with other brain areas supporting socially, emotionally, and cognitively relevant functions, and uncovers a set of brain areas stunningly similar to the network implementing high-level social cognition in humans.

HFSP Long-Term Fellow Caspar Schwiedrzik and HFSP Program Grant holder Winrich Freiwald and colleagues
authored on Thu, 19 November 2015

Macaque monkeys transmit a multitude of social signals through their faces. It is thus no wonder that they dedicate a large portion of their visual system to the processing of facial information. While we have quite a good understanding of the inner workings of this dedicated face processing network, the so-called “face patch system”, we do not yet know how information about faces is exchanged with other brain areas so that a face can evoke an emotion, activate a memory, or draw attention. Here, we identified brain regions with which face areas can communicate by measuring functional connectivity through whole-brain functional magnetic resonance imaging.

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We find that the core face processing areas in monkeys are functionally connected to several other brain areas within frontal, temporal, and parietal cortices, as well as subcortical structures, supporting socially, emotionally, and cognitively relevant functions. By revealing the embedding of face areas into larger brain networks, we can show that these areas form an extended face-processing network, similar to what has been found in humans.

While humans and macaque monkeys share much of their face processing abilities, it is an open question to what extent they share socio-cognitive skills. For example, while humans routinely and frequently infer what others think or want, it remains debated whether monkeys have this ability. Even more so, the question whether the macaque brain actually contains the brain regions that support high-level social cognition in humans is controversial.

We made use of the fact that functional magnetic resonance imaging can be used in monkeys and in humans, and customized an analysis that identifies high-level social cognition areas in humans to be suitable to identify such regions in the monkey brain. Specifically, in humans, the so-called “social brain” intersects with another large-scale network, the default mode network. We then assessed, using the monkey extended face processing network as a proxy for the social brain, whether and where a similar overlap exists in the macaque brain. The intersection of the monkey extended face processing network and the default mode network identified a pattern of brain regions astonishingly similar to the brain regions that implement the most high-level forms of social cognition, such as understanding others’ thoughts and feelings, in humans, located in the posterior upper bank of the superior temporal sulcus, medial parietal, and medial prefrontal cortex.

The results of this novel approach suggest that assessing functional connectivity of the face patch system offers a new, easily accessible avenue with which to probe the social brain, and point to a deep evolutionary heritage of human abilities for social cognition.

Reference

Face Patch Resting State Networks Link Face Processing to Social Cognition. Schwiedrzik CM, Zarco W, Everling S, Freiwald WA (2015)  PLoS Biol 13(9): e1002245. doi:10.1371/journal.pbio.1002245.

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