The primate hippocampus constructs a dynamic internal model of rhythmic events

The hippocampus contributes to the formation of internal representations that organize experience across space and time. Yet how it represents events that unfold continuously, especially when sensory input is absent and dynamics must be internally sustained, remains unclear. We recorded single-neuron and local field potential activity in the hippocampus of rhesus monkeys performing a metronome task in which a visual stimulus alternated rhythmically between two spatial locations and then had to be tracked internally without external cues. Hippocampal neurons exhibited tempo-scaled oscillatory firing patterns that correlated with stimulus location during a visible entrainment and an internal maintenance epoch. These dynamics compressed or stretched to match interval duration and were accompanied by broadband LFP power modulations that also scaled with tempo. In error trials oscillatory activity showed systematic phase shifts, and oscillation-related population components were attenuated, suggesting that hippocampal dynamics reflected the animals' internal estimates of stimulus position. Regression analyses revealed mixed selectivity, with firing rates influenced by spatial alternation, tempo context, elapsed time, and task epoch. These findings indicate that hippocampal populations generate dynamical activity that continuously track and predict the evolving spatiotemporal structure of ongoing events. Rather than representing time as an isolated variable, the primate hippocampus implements a predictive internal model linking temporal structure, spatial information, and contextual state to guide behavior in the absence of sensory input.