Non‑monotonic reorganization of cortical neuron firing despite ongoing delta‑dominated activity

Delta-dominated activity is a hallmark of anesthesia and non‑REM sleep, yet how neuronal firing evolves across these rhythms remains unclear. Here, by tracking cortical neuron firing in the ketamine‑xylazine model, we find that across continuing delta-dominated activity, population firing rates progress through successive epochs of excitation, suppression, and re-emergence. Concurrently, fine‑scale spike timing and burst dynamics exhibit non-monotonic modulation, revealing continuous reorganization beneath the ongoing delta-dominated oscillation.

At the transition to theta-dominated activity, a restructuring of temporal patterning without a significant shift in the firing-rate distribution suggests that temporal structure, rather than firing rate, defines this transition. These population-level dynamics were firing-rate-dependent: high‑firing-rate neurons were more tightly modulated, whereas low‑firing-rate neurons exhibited more heterogeneous changes. Neither ketamine nor xylazine alone recapitulates these dynamics, suggesting their combined action creates a uniquely dynamic architecture.

These findings reveal a continuous, firing-rate-dependent reorganization of single-neuron activity during ongoing delta-dominated states. This work was supported by Scientific Foundation for Youth Scholars of Shenzhen University (to D.G). These authors contributed equally: Dengyun Ge, Shanlin Qin.

School of Basic Medical Sciences, Shenzhen University Medical School, Shenzhen, China Dengyun Ge, Zixuan Huang, Lichao Chen & Yi Liu Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China The authors declare no competing interests. Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. Open Access This article is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License, which permits any non-commercial use, sharing, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if you modified the licensed material.

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To view a copy of this licence, visit http://creativecommons.org/licenses/by-nc-nd/4.0/. Ge, D., Qin, S., Huang, Z. et al. Non‑monotonic reorganization of cortical neuron firing despite ongoing delta‑dominated activity.