Spatiotemporal coordination of specialized cerebellar networks supports episodic memory in older adults

Abstract

Episodic memory decline in ageing is typically attributed to the cortico-hippocampal system, yet the cerebellum’s specific contribution via cerebellar-cerebral circuits remains underexplored. We analysed task-based fMRI data from 821 older adults, including a longitudinal subset of 78 participants followed for four years. Using sparse dictionary learning on task-responsive activity, we identified three non-motor networks: a bilateral lobule VI/Crus I mnemonic-monitoring network, a right lobule Crus I/II default-mode-aligned network, and a right lobule VIIb/VIIIa evidence-evaluation network. While network recruitment varied with task demands and associated with memory performance, phase-specific static cerebellar–cerebral functional connectivity showed stable organization but limited behavioural specificity. In contrast, dynamic functional connectivity patterns effectively distinguished memory-performance groups. Crucially, greater instability in dynamic functional connectivity during encoding predicted longitudinal retrieval slowing. These findings suggest that preserved episodic memory in older adults is supported by the spatiotemporal coordination of specialized cerebellar networks with distributed cerebral networks.