Representational differentiation and integration within the hippocampal circuit during naturalistic stimuli

The hippocampus is essential for transforming dynamic experiences into structured knowledge, forming internal models of the world that guide planning, decision-making, and behavior. Recent research has demonstrated that complementary hippocampal mechanisms-specifically, the differentiation of distinct experiences and the integration of related information-fundamentally underlie cognitive map formation during spatial navigation. However, there is limited empirical evidence on how these processes support network-based, map-like representations during complex continuous stimuli. Here, using the Human Connectome Project 7T naturalistic dataset, we explored how the canonical hippocampal circuit (DG-CA3-CA1) supports differentiation and integration from movie stimuli. Our results found that the hippocampus encoded both semantic features and small-world network representations from movie stimuli. Moreover, we observed representational differentiation in geodesic network distances within the DG-CA3 pathway, while integration predominated in the CA3-CA1 pathway. Inter-subject functional correlation analysis revealed that stronger hippocampal-cortical connectivity-especially with the retrosplenial cortex, parahippocampal cortex, medial prefrontal cortex, and visual regions-was positively correlated with CA3-CA1 integration capacity. Notably, CA1-retrosplenial connectivity emerged as a key mediator linking hippocampal integration to individual cognitive performance. These insights reveal how the hippocampus dynamically differentiates and integrates movie information, highlighting the importance of hippocampal-retrosplenial interactions in linking hippocampal integration processes with cognitive abilities.