Cerebellar engagement for narrative comprehension in Chinese-English bilinguals

The cerebellum, traditionally regarded as a part of the motor network, has recently been implicated in higher-level language processing and narrative comprehension. However, its role in complex bilingual narrative comprehension remains unexplored. A critical question is whether the cerebellum maintains consistent functional profiles across languages or adapts flexibly. In this study, we investigated the cross-language consistency and language-specific modulations in cerebellar activation and cortico-cerebellar functional connectivity in highly proficient Chinese-English bilinguals (N = 28) while they completed a narrative comprehension task in their first (L1) and second (L2) language. We found that the right posterior cerebellum, particularly the Crus I and Crus II, exhibited spatially consistent activation during narrative comprehension in both languages. Compared to meaningless material processing, this region showed increased connectivity with the cortical default mode network (DMN) during narrative comprehension, with significantly stronger connectivity with DMN during L1 processing compared to L2. Additionally, the connectivity between the narrative-sensitive cerebellar regions and the left inferior frontal gyrus (IFG) was positively correlated with L2 age of acquisition (AoA) during L2 processing. This association between the cerebellum with L2 AoA suggests that the cerebellum undergoes bilingual experience-dependent adaptations to support bilingual language processing. Our results suggest that the cerebellum flexibly adjusts its connectivity and pattern with the cerebral cortex during narrative comprehension across languages. The enhanced cortico-cerebellar collaboration during L2 processing reflects a compensatory neural mechanism tied to L2 AoA. This study underscores the cerebellum's flexible functional mechanisms in bilingual narrative comprehension and its adaptive role in late L2 acquisition.