Role of the posterolateral cerebellum in language.

Historically, scientists have believed that the cerebellum controls only movement. However, recent evidence from neuroimaging and human lesion studies suggests that the right posterolateral cerebellar hemisphere is involved, independently of movement, in helping an individual to generate verbs for given nouns. We sought to elucidate the key factors contributing to the verb generation deficits of subjects with right posterolateral cerebellar damage and thus to better understand the specific contributions of the postero-lateral cerebellum to language. We compared the performance of subjects with focal left-sided posterolateral cerebellar lesions, those with focal right-sided posterolateral cerebellar lesions, and neurologically normal pilot control subjects on an antonym generation task, noun (category member) generation task, verb selection task, and lexical decision task. Preliminary results show that subjects with right cerebellar lesions are impaired relative to other subjects only on the antonym generation task. The results provide evidence that the right cerebellar language deficit is not due solely to deficits in "mental movement" coupled to a verb and that internal generation of a word seems to be a key factor in eliciting a deficit. In addition, a semantic processing demand may be necessary but insufficient to elicit a right cerebellar language deficit. The results support the theory that the right posterolateral cerebellar hemisphere assists the left cerebral hemisphere in helping an individual learn to generate specific types of spoken, two-word associations. The full nature of this process awaits further investigation.