The contribution of the cerebellum to speech processing

Lesions to or diseases of the cerebellum may disrupt the motor components of speech production both at the segmental and suprasegmental level giving rise to "ataxic dysarthria", a syndrome characterized, among others, by slowed speaking rate, distorted consonant and vowel productions and impaired prosodic modulation of sentence utterances. The concept of ataxic dysarthria has been further refined by measurements at the acoustic speech signal, tracking of articulatory movements and preliminary functional imaging studies. In summary, the available parametric data indicate the cerebellum to support several aspects of speech processing: acceleration of orofacial gestures, timing (coordination) of complex articulatory sequences, presumably, in cooperation with the anterior perisylvian language zone and control of brainstem reflexes monitoring respiratory and laryngeal muscle activity. Lesion studies and functional imaging indicate superior aspects of the cerebellum to mediate the speech motor functions referred to. Laterality and extent of the respective representation area, presumably, depend upon task demands. Besides speech motor deficits, recent investigations found disrupted speech perception in cerebellar subjects in terms of impaired categorization of specific durational minimal pairs. (C) 2000 Elsevier Science Ltd. All rights reserved.