Speech, language, and the cerebellum.

The cerebellum can affect speech and language in a number of ways. The most obvious is dysarthria when motor movements are deprived of the regulatory control, which is one of the main functions of the cerebellum. Less well-known is cerebellar mutism, which most often occurs after the removal of a cerebellar tumour. It is unlikely that this is simply the result of dysarthria. The most controversial aspect of cerebellar function, and the main stress of this paper, is the contribution it may make to language production. A number of studies have suggested that the cerebellum can, indeed, be involved in both cognition and language. A number of these are reviewed, in particular, the results of diffuse and focal lesions of the cerebellum, and how these can affect the function of the cerebrum; and conversely how cerebral lesions can cause changes in the cerebellum. Positron emission tomography (PET) has been essential in the assessment of these patients. During human evolution parts of the cerebellum and their connections have enlarged enormously, and it would be surprising if these parts of the brain had not taken on new roles. To regard the cerebellum as only serving motor function is too narrow a concept.