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Granule cells reorient cortical trajectories to separate contexts

Published: 08/26/2026, 12:00 AM

Nature (2026) Cite this article To learn effectively, animals must generalize across related contexts yet distinguish between them. Generalization relies on low-dimensional neural manifolds throughout the neocortex1,2, which accelerate learning by constraining neural activity to task-relevant axes3.Conversely, context separation is thought to depend on neural expansion layers that can project information into high-dimensional feature spaces4,5, most famously cerebellar granule cells (GrCs)6,7,8. Here, to investigate the generalization–separation trade-off, we simultaneously imaged key nodes in the universal cortico-cerebellar pathway9—premotor layer 5 pyramidal tract (L5PT) and GrCs—in mice during parallel learning of two distinct skills with a shared temporal structure. Rather than expanding the cortical representations, GrCs retained their low-rank encoding of each task. Across contexts, despite stable cortico-cerebellar coupling, L5PT activity patterns generalized, whereas GrC patterns temporally remapped. But rather than independently scrambling, GrC populations remapped coherently: their low-dimensional trajectories ‘rotated’ apart between tasks, separating the contexts while preserving the cortical geometry of each. Moreover, GrC trajectories diverged most strongly in expert mice. This suggests a fundamental architectural division of labour: the cortex provides invariant dynamic primitives for smooth generalization, whereas cerebellar activity reconfigures them to drive context-specific output. This is a preview of subscription content, access via your institution Access Nature and 54 other Nature Portfolio journals Get Nature+, our best-value online-access subscription Prices may be subject to local taxes which are calculated during checkout The data in this study have been publicly deposited in Dryad at https://doi.org/10.5061/dryad.9p8cz8x0p (ref. 59). Source data are provided with this paper. Code is publicly available via Zenodo at https://doi.org/10.5281/zenodo.21341571 (ref. 60). Bernardi, S. et al. The geometry of abstraction in the hippocampus and prefrontal cortex. Cell 183, 954–967 (2020). Article CAS PubMed PubMed Central Google Scholar