The cerebellum and language: evidence from patients with cerebellar degeneration.

Clinical and imaging studies suggest that the cerebellum is involved in language tasks, but the extent to which slowed language production in cerebellar patients contributes to their poor performance on these tasks is not clear. We explored this relationship in 18 patients with cerebellar degeneration and 16 healthy controls who completed measures of verbal fluency (phonemic and semantic), word stem completion, and oral naming speed. Cerebellar patients showed significantly slower response times when naming common nouns, which correlated with their degree of motor impairment. Patients were significantly impaired on both phonemic and semantic fluency measures compared to controls (p<0.001), even when naming speed was entered as a covariate (p=0.03). On the word stem completion task, patients were significantly less accurate (p<0.001), had more errors due to non-responses (p=0.008), and were slower to respond (p=0.036) than controls; group effects were significant for overall accuracy, but not response time, when the effects of naming speed were covaried (p=0.014). These findings suggest that cerebellar patients' poorer performance on language tasks cannot be explained solely by slower language production, and that the integrity of cerebellar-prefrontal loops might underlie poorer performance on measures of executive function in cerebellar patients.