However, where the corticospinal tract is dominant (as in primates), the rubrospinal tract may be considered to be vestigial. Therefore, here the red nucleus is less important in motor functions than in many other mammals. However, 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 sparse control over hands, as the rubrospinal tract is more involved in large muscle movement such as that for arms (but not 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 (rather it relies on the corticospinal tract). The majority of red nucleus axons do not project to the spinal cord, but instead (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.
The red nucleus receives many inputs from the cerebellum (interposed nucleus and the lateral cerebellar nucleus) of the opposite side and an input from the motor cortex of the same side.
The red nucleus has two sets of efferents:-
In humans, the majority of the output goes to the bundle of fibers continues through the medial tegmental field toward the inferior olive of the same side, to form part of a pathway that ultimately influence the cerebellum.