article published yes Lars Bollmann author 47AD3038-F248-11E8-B48F-1D18A9856A87 Peter Baracskay author 361CC00E-F248-11E8-B48F-1D18A9856A87 Federico Stella author 39AF1E74-F248-11E8-B48F-1D18A9856A870000-0001-9439-3148 Jozsef L Csicsvari author 3FA14672-F248-11E8-B48F-1D18A9856A870000-0002-5193-4036 JoCs department Memory-related information processing in neuronal circuits of the hippocampus and entorhinal cortex project Interneuro plasticity during spatial learning project Hippocampal reactivation of waking neuronal assemblies in sleep is a key initial step of systems consolidation. Nevertheless, it is unclear whether reactivated assemblies are static or whether they reorganize gradually over prolonged sleep. We tracked reactivated CA1 assembly patterns over ∼20 h of sleep/rest periods and related them to assemblies seen before or after in a spatial learning paradigm using rats. We found that reactivated assembly patterns were gradually transformed and started to resemble those seen in the subsequent recall session. Periods of rapid eye movement (REM) sleep and non-REM (NREM) had antagonistic roles: whereas NREM accelerated the assembly drift, REM countered it. Moreover, only a subset of rate-changing pyramidal cells contributed to the drift, whereas stable-firing-rate cells maintained unaltered reactivation patterns. Our data suggest that prolonged sleep promotes the spontaneous reorganization of spatial assemblies, which can contribute to daily cognitive map changes or encoding new learning situations. https://research-explorer.ista.ac.at/download/19506/20133/2025_Neuron_Bollmann.pdf application/pdfno Elsevier2025 eng 0896-6273 1097-4199 40132588 00151044040000110.1016/j.neuron.2025.02.025 11391446-1459.e6 https://ista.ac.at/en/news/how-sleep-keeps-our-memories-fresh/ Bollmann L, Baracskay P, Stella F, Csicsvari JL. Sleep stages antagonistically modulate reactivation drift. <i>Neuron</i>. 2025;113(9):1446-1459.e6. doi:<a href="https://doi.org/10.1016/j.neuron.2025.02.025">10.1016/j.neuron.2025.02.025</a> Bollmann, L., Baracskay, P., Stella, F., &#38; Csicsvari, J. L. (2025). Sleep stages antagonistically modulate reactivation drift. <i>Neuron</i>. Elsevier. <a href="https://doi.org/10.1016/j.neuron.2025.02.025">https://doi.org/10.1016/j.neuron.2025.02.025</a> Bollmann, Lars, Peter Baracskay, Federico Stella, and Jozsef L Csicsvari. “Sleep Stages Antagonistically Modulate Reactivation Drift.” <i>Neuron</i>. Elsevier, 2025. <a href="https://doi.org/10.1016/j.neuron.2025.02.025">https://doi.org/10.1016/j.neuron.2025.02.025</a>. Bollmann, Lars, et al. “Sleep Stages Antagonistically Modulate Reactivation Drift.” <i>Neuron</i>, vol. 113, no. 9, Elsevier, 2025, p. 1446–1459.e6, doi:<a href="https://doi.org/10.1016/j.neuron.2025.02.025">10.1016/j.neuron.2025.02.025</a>. L. Bollmann, P. Baracskay, F. Stella, and J. L. Csicsvari, “Sleep stages antagonistically modulate reactivation drift,” <i>Neuron</i>, vol. 113, no. 9. Elsevier, p. 1446–1459.e6, 2025. Bollmann L, Baracskay P, Stella F, Csicsvari JL. 2025. Sleep stages antagonistically modulate reactivation drift. Neuron. 113(9), 1446–1459.e6. L. Bollmann, P. Baracskay, F. Stella, J.L. Csicsvari, Neuron 113 (2025) 1446–1459.e6. 195062025-04-06T22:01:32Z2026-04-28T13:39:22Z