Aging is associated with uniform structural decline across cerebellar regions while preserving topological organization and showing no relation with sensorimotor function

Aging affects cerebellar structure, yet the regional specificity of this decline and its relationship to sensorimotor function remain unclear. In this study, we quantified age-related gray matter differences in 50 young and 80 older adults using both anatomically defined cerebellar parcellations and a functionally defined cerebellar atlas. Across both anatomical and functional parcellations, older adults showed robust reductions in gray matter volume relative to young adults. However, contrary to prior reports of region-specific vulnerability, age effects did not differ significantly across regions: both datasets demonstrated remarkably uniform gray matter decline. Structural covariance analyses revealed that correlations between cerebellar regions were determined primarily by spatial proximity and, to a lesser extent, by medial-lateral (vermis-hemisphere) organization or functional similarity. Importantly, the topological organization of the cerebellum remained stable across age groups, indicating preserved structural coordination despite widespread gray matter loss. Finally, despite substantial interindividual variability in behavioral, regional cerebellar gray matter volumes, whether anatomically or functionally defined, did not predict inter-individual variability for any of our eight cerebellum-dependent outcomes. This absence of structure-function relationships suggests that behavioral performance is maintained through compensatory mechanisms or microstructural features not captured by regional gray matter volume. Together, the results demonstrate uniform age-related cerebellar degeneration alongside preserved topological organization and no measurable impact on cerebellar sensorimotor function, supporting the notion of a robust cerebellar reserve throughout healthy aging.