Neural Trajectories of Conceptually Related Events

In a series of conceptually related episodes, meaning arises from the link between these events rather than from each event individually. How does the brain keep track of conceptually related sequences of events (i.e., conceptual trajectories)? In a particular kind of conceptual trajectory--a social relationship--meaning arises from a specific sequence of interactions. To test whether such abstract sequences are neurally tracked, we had participants complete a naturalistic narrative-based social interaction game, during functional magnetic resonance imaging. We modeled the simulated relationships as trajectories through an abstract affiliation and power space. Using two independent samples (n = 50), we found evidence of both the underlying social dimensions of affiliation and power and the evolving social relationships themselves as being tracked by the hippocampus. These results suggest that our evolving relationships with others, despite being composed of isolated events that occur independently across time and space (i.e., spatially and temporally non-consecutive events), but are nevertheless related conceptually, are represented in trajectory-like neural patterns in the human hippocampus.