Medial temporal lobe encodes cognitive maps of real-world social networks
People routinely navigate their complex social networks1: From gossiping strategically with others2-4 to brokering connections between siloed groups5,6, our ability to make adaptive social choices hinges on whether we can construct useful mental representations of the social ties within our communities7. While decades of neuroscience research have shown that the medial temporal lobe encodes cognitive maps of physical8-10 or conceptual space11, how the brain represents our social networks in the wild to solve social problems remains unknown. By combining computational models with functional neuroimaging and longitudinal measurement of an evolving and densely interconnected real-world human network (N=187), we show that the entorhinal cortex encodes a cognitive map of the long-range connectivity between pairs of network members. This social map reflects the particular demands of social navigation and is specifically formatted to encode the simultaneous connectivity between network members, which critically enables tracking how information diffuses across the network. Moreover, the strength of its encoding in the entorhinal cortex aids in brokering connections that improve cohesion within peoples social communities. Our results illuminate how a domain-general neural mechanism12,13 is tailored to prioritize the natural dynamics of social phenomena in order to support adaptive navigation through these highly complex environments.