In a
vertebrate without a significant
corticospinal tract,
gait is mainly controlled by the red nucleus. However, in
primates, where the
corticospinal tract is dominant, the
rubrospinal tract may be regarded as vestigial in motor function. Therefore, the red nucleus is less important in primates than in many other mammals. Nevertheless, the
crawling of
babies is controlled by the red nucleus, as is arm swinging in typical walking. The red nucleus may play an additional role in controlling muscles of the
shoulder and upper arm via projections of its magnocellular part. In humans, the red nucleus also has limited control over
hands, as the
rubrospinal tract is more involved in large muscle movement such as that for the arms (but not for the legs, as the tract terminates in the superior thoracic region of the spinal cord). Fine control of the
fingers is not modified by the functioning of the red nucleus but relies on the
corticospinal tract. The majority of red nucleus axons do not project to the
spinal cord but, via its parvocellular part, relay information from the
motor cortex to the
cerebellum through the
inferior olivary complex, an important relay center in the
medulla. ==Input and output==