Humans, along with many other social animals, form complex societies by remembering individuals and demonstrating appropriate behaviours towards them. The ability to remember and recognize others facilitates the development of adaptive social structures. For example, the formation of mating pairs and the establishment of hierarchies to avoid unnecessary conflict both rely on social memory and the ability to assign specific values or importance to these memories. Since the seminal study of patient H.M. in 1957, which highlighted the critical role of the hippocampus in episodic memory, subsequent research on patients with hippocampal or medial temporal lobe (MTL) damage has further underscored its importance in both social memory and memories involving spatiotemporal contexts.

A groundbreaking study that substantially advanced our understanding of social memory and its representation in the human hippocampus was the discovery of ‘concept cells’ by Quiroga et al. in 2005. Quiroga determined that neurons in the human MTL, particularly in the anterior hippocampal region, exhibit remarkably selective responses to images of specific individuals, such as the actor Halle Berry. What is particularly fascinating about this finding is that a substantial proportion of these MTL neurons respond not only to pictures of the individual, but also to written names (for example, the letter string ‘Halle Berry’), and even to a synthesized voice pronouncing the individual’s name. This demonstrates the complex and multifaceted nature of how our hippocampal neurons encode and recall familiar individuals, suggesting that they do so by integrating multimodal information in a highly selective manner. Specifically, MTL neurons encode an abstract representation of the concepts associated with the stimulus.