Anatomical evidence for an ipsilateral rubrospinal pathway and for direct rubrospinal projections to motoneurons in the cat.

In 11 cases [3H]leucine injections were made in various parts of the red nucleus (NR) and surrounding area. The autoradiographical tracing results confirmed the existence of a somatotopic organization in the location of the rubrospinal neurons. Moreover the results demonstrated direct NR projections to the most dorsolaterally located motoneuronal cell group in the C8 and upper T1 spinal segments and some ipsilaterally descending rubrospinal fibers terminating in the lateral part of the cervical intermediate zone.