The Primate Hippocampus Constructs a Temporal Scaffold Anchored to Behavioral Events

The hippocampus has been shown to support a variety of cognitive functions, ranging from spatial navigation^1,2 to anxiety regulation³ to memory formation^4,5, but how its moment-to-moment neuronal activity contributes to cognition remains poorly understood. The activity of single hippocampal neurons is correlated with numerous perceptual features and task variables^6-14, raising the question of whether these response properties reflect distinct mechanisms or a single generalized computation. Here, we show that diverse hippocampal responses reflect unified event-driven dynamics in which population activity transitions between discrete ensemble states at behaviorally salient events. Recording from monkeys performing a virtual spatial alternation task, we found that population activity did not evolve smoothly over time but instead transitioned abruptly at each relevant event. These discontinuities segmented activity into distinct ensemble codes, effectively chunking conceptually defined task epochs. Notably, many neuronal responses persisted across visually distinct environments, demonstrating that these dynamics reflect abstract task structure rather than specific sensory features. These results reveal that the hippocampus constructs a temporal scaffold anchored to relevant behavioral events, with each neural state tracking a distinct task phase. This organizational principle may explain the diverse correlates observed across studies: rather than individually encoding task features, hippocampal neurons collectively signal which phase of a behavioral sequence is currently active. Our findings suggest that the hippocampus parses experience into meaningful elements and tracks "position" within a learned behavioral structure.