The cerebellar projection of the peri-hypoglossal nuclei (nucleus intercalatus, nucleus praepositus hypoglossi and nucleus of roller) in the cat.

The cell groups immediately surrounding the nucleus of the hypoglossal nerve in the cat may be subdivided into three nuclei: the nucleus intercalatus, the nucleus praepositus hypoglossi, and the nucleus of Roller. They will here be collectively referred to as the peri-hypoglossal nuclei. In a previous study (7) it was shown that a considerable proportion of the cells of these nuclei send their neurites into the cerebellum, since typical retrograde (axonal) changes consistently occurred in them following decerebellations or large cerebellar lesions. The connection was determined to be crossed as well as uncrossed, with some preponderance of the uncrossed component. Furthermore, cells of all types (large, medium-sized and small ones) send processes into the cerebellum. The findings indicate that these nuclei are functionally related to motor activities of the tongue, rather than to taste, as has been suggested by some authors. The present study was undertaken in an attempt to determine the perihypoglossal-cerebellar projection in more detail, since it would be of interest to know whether these fibers are distributed to all parts of the cerebellum or only to particular areas, and if so, to which areas or lobules. Furthermore, the question as to whether the different nuclei of the peri-hypoglossal complex project onto the same or different cerebellar areas deserves attention.