Red nucleus

The red nucleus is a structure in the rostral midbrain involved in motor coordination. In animals without a significant corticospinal tract, gait is mainly controlled by the red nucleus. In humans, the red nucleus mainly controls the muscles of the shoulder and upper arm, but it has some control over the lower arm and hand as well. It is less important in its motor functions for humans than in many other mammals, because, in humans, the corticospinal tract is dominant. However the crawling of babies is controlled by the red nucleus, as is arm-swinging in normal walking. Because the red nucleus has little control over the hands, fine control of the fingers is impaired should only the red nucleus be functioning.

The red nucleus receives many inputs from the contralateral cerebellum and an input from the ipsilateral motor cortex, and sends efferent axons (the rubrospinal projection) to the contralateral half of the rhombencephalic reticular formation and spinal cord. These efferent axons cross just ventral to the nucleus and descend through the midbrain to the spinal cord, where the rubrospinal tract which they make up runs ventral to the lateral corticospinal tract in the lateral funiculus.