The rubrospinal tract in a prosimian primate, Galago senegalensis.

The spinal distribution of rubrospinal fibers is described in the lesser bushbaby (Galago senegalensis), a prosimian primate. The tract is composed of thick and thin fibers, extends the length of the cord in the lateral funiculus, and is located ventral and ventrolateral to the lateral corticospinal tract and medial to the dorsal spincerebellar tract. There is a topographical relationship between origin and termination of rubrospinal fibers in Galago. Dorsomedial areas of the red nucleus project primarily to contralateral lumbar and sacral levels. Thoracic fibers arise from intermediate regions of the nucleus. Rubrospinal fibers in Galago terminate in basilar regions of the dorsal horn mainly at cervical and lumbar levels. Degeneration is most concentrated in medial and lateral portions of lamina V-VII. Although degenerated fibers approached the midline, none could be traced to the contralateral side. Lesions of more extensive portion of the nucleus resulted in degeneration in Clarke's column especially evident in low thoracic and upper lumbar levels. The latter connection may represent one rubrocerebellar feedback loop in the lesser bushbaby.