Organization of the cerebellar tongue representation in the monkey

The cerebellar nuclei of rhesus monkeys were stimulated electrically and evoked responses of the tongue recorded with force-displacement transducers and electromyographically. Stimulation of the dentate (DN) and fastigial (FN) nuclei produced different effects on the tongue musculature, the former evoking movements characterized by changes in both the lateral and anteroposterior (AP) dimensions of the tongue and the latter movements associated with a preferential change in the AP dimension. While all three deep nuclei influenced the genioglossus muscle, the influences varied across nuclei in the following manner: FN produced the largest amplitude genioglossus mediated AP excusions and DN the smallest, with the nucleus interpositus (NI) occupying an intermediate position; and, FN and medial NI stimulation evoked changes in genioglossus respiratory activity whereas DN stimulation did not. These data indicate that the cerebellar tongue representation is organized into different functional zones and that within an anatomically broad representation of a single target muscle, nuclear functional specificity exists.