The cerebellum is sensitive to the lexical properties of words during spoken language comprehension

Over the past few decades, research into the function of the cerebellum has expanded far beyond the motor domain. A growing number of studies are probing the role of specific cerebellar subregions, including Crus I and Crus II, in higher-order cognition, though their involvement in speech and language processing remains underspecified. In the current fMRI study, we show evidence of the cerebellum’s sensitivity to variation in two well-studied psycholinguistic properties of words—lexical frequency and phonological neighborhood density—during passive, continuous listening of a podcast. To determine whether, and how, activity in the cerebellum correlates with these lexical properties we modeled each word separately using an amplitude-modulated regressor; time-locked to the onset of each word. At the group level, significant effects of both lexical properties landed in expected cerebellar subregions—Crus I and Crus II. The BOLD signal correlated with variation in both lexical properties, consistent how they are thought to affect the ease of word recognition. Activation patterns at the individual level also showed that the most probable sites for effects of phonological neighborhood and lexical frequency landed in Crus I and Crus II, though there was significant variability. These results suggest that the functional loci for these effects, especially frequency effects, can emerge in cerebellar subregions that vary across individuals. Although the exact cerebellar mechanisms used during speech and language processing are not yet evident, these findings highlight the cerebellum’s role in word-level processing during continuous listening.