DOES THE CEREBELLUM CONTRIBUTE TO COGNITIVE ASPECTS OF SPEECH PRODUCTION - A FUNCTIONAL MAGNETIC-RESONANCE-IMAGING (FMRI) STUDY IN HUMANS

Several positron emission tomography (PET) studies suggest a contribut ion of the lateral aspects of the right cerebellar hemisphere to highe r-level (cognitive) aspects of speech production such as controlled ve rbal response selection. As an alternative, however, 'inner speech', g iving rise to subliminal activity of orofacial and laryngeal muscles, might account for the observed activation effects. Eighteen subjects u nderwent functional magnetic resonance imaging (fMRI) during continuou s silent recitation of the names of the months of the year ('automatic speech'). The right cerebellar hemisphere showed a significantly incr eased hemodynamic response concomitant with, among others, an asymmetr ic activation pattern towards the left side at the level of the motor strip. Since highly overlearned word strings, presumably, pose few dem ands on controlled response selection and since the projections of the right cerebellar hemisphere to the left precentral gyrus participate in motor control, the observed cerebellar activation, thus, seems to b e related to the articulatory level of speech production rather than, as suggested by previous PET studies, to cognitive operations. (C) 199 8 Elsevier Science Ireland Ltd.