Multi-timescale dynamics organize descending pain modulation

Summary Effective pain therapies increasingly target neural circuits that regulate nociceptive processing, yet how descending control systems regulate pain across time remains poorly understood. Because pain regulation must coordinate rapid defensive responses with slower fluctuations in physiological state, these neural circuits are likely to operate across multiple timescales. However, whether such dynamics exist in brainstem pain-control circuits remains largely unknown. We investigated this question in populations of rostral ventromedial medullary (RVM) neurons. The RVM contains ON- and OFF-cells that exert descending control over spinal nociceptive transmission, regulating pain sensitivity and behavioral responses to threat. Combining neuronal recordings with probabilistic modeling, we show that RVM ON- and OFF-cells operate across distinct timescales. During noxious stimulation, population responses unfold through structured multi-phase dynamics with rapid activation followed by prolonged recovery over tens of seconds. In the absence of stimulation, the same neurons display coherent quasi-periodic fluctuations in firing activity on the order of minutes. Gaussian-process models show that these slow dynamics are predictable from past activity, indicating structured temporal organization beyond stimulus-evoked responses. These findings demonstrate that intrinsic network dynamics spanning seconds to minutes organize activity in descending pain-modulatory neurons. This temporal organization indicate that descending pain-control circuits integrate rapid pain-related signaling with slower fluctuations in physiological state, revealing an intrinsic dynamical framework for descending pain modulation. Significance Pain regulation requires coordination between rapid defensive responses and slower changes in physiological state, yet how these processes are integrated in the brain remains unclear. We show that neurons in a key brainstem pain-control center, the rostral ventromedial medulla, operate across multiple timescales. Using neuronal recordings and computational modeling, we find that the same neurons exhibit both fast responses to painful stimuli and slow, structured fluctuations in ongoing activity. These results demonstrate that descending pain control is temporally organized rather than purely reactive. This provides a framework for understanding how pain is regulated over time and highlights temporal dynamics as a potential target for pain therapies. Competing Interest Statement The authors have declared no competing interest. Footnotes This version of the manuscript has been revised with an updated abstract and minor textual clarifications and improvements.