Rapid expansion and renormalization of parietal gray matter volume following associative learning

The human brain exhibits rapid structural plasticity following learning, yet its temporal dynamics and behavioral relevance remain elusive, particularly for declarative forms of learning. In this study, we tested whether T1-weighted MRI captures rapid structural reorganization following associative memory formation and whether such changes follow an expansion–renormalization trajectory. We combined three independent datasets (N = 198) to quantify gray matter volume (GMV) changes following an associative memory task using voxel-based morphometry across baseline, 2 h, and 12 h post-learning.

We observed GMV increases in parietal, lateral occipital, and cerebellar regions at 2 h post-learning (n = 139), which were no longer detectable relative to baseline at 12 h (n = 96), consistent with rapid renormalization. Critically, GMV changes in left parietal cortex were further linked to how well participants retained the memory, such that greater maintenance of GMV was associated with better retention (n = 37). By contrast, in a distinct right parietal region (n = 32; 17 sleep, 15 wake), GMV increased in the sleep group in the control but not in the learning condition, whereas GMV change did not differ between conditions in the wake group.

This sleep-related effect was unrelated to memory retention. Our findings suggest that human gray matter undergoes hour-scale changes, with potentially dissociable memory- and sleep-related components. The authors want to thank all participants and students supporting the data collection, as well as the CoreFacility ‘Magnetic Resonance Development and Application Center Freiburg (MRDAC)’, Department of Radiology University Medical Center Freiburg, Faculty of Medicine, University of Freiburg, for support in acquisition of the data.

We further thank Arno Villringer from the Max-Planck-Institute Leipzig for fruitful discussion on the biology underlying observed MR signal changes. Open Access funding enabled and organized by Projekt DEAL. D.K. received funding from the Klaus Tschira Boost Fund, a joint initiative of GSO—Guidance, Skills & Opportunities e.V. and Klaus Tschira Stiftung (grant number: GSO/KT54), the Else Kröner-Fresenius Stiftung (2024_EKEA.18) and was also supported by Deutsche Forschungsgemeinschaft (DFG, German Research Foundation)—grant: KU 4553/2-1.

D.K. is grateful to the Baden-Württemberg Stiftung for the financial support of this research project through the Postdoctoral fellowship for leading early career researchers. M.S. was supported by Deutsche Forschungsgemeinschaft (DFG, German Research Foundation)—grant: SCHO1820/2—1, Project number: 426865207. We further thank Deutsche Forschungsgemeinschaft DFG for financial support of the Siemens Cima.X MRI site ‘INST 39/1365-1 FUGG’.

Institute of Psychology, Neuropsychology, University of Freiburg, 79106, Freiburg im Breisgau, Germany Felix Kleinschroth, Stella Villa, Antonia Lenders, Monika Schönauer & Deniz Kumral BrainLinks-BrainTools, University of Freiburg, 79106, Freiburg im Breisgau, Germany Bernstein Center Freiburg, University of Freiburg, 79106, Freiburg im Breisgau, Germany Max Planck Institute for Biological Cybernetics, 72076, Tübingen, Germany Institute of Medical Psychology and Behavioral Neurobiology, University of Tübingen, 72076, Tübingen, Germany The authors declare no competing interests. Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. Below is the link to the electronic supplementary material.