Rubrospinal tract

The rubrospinal tract is a part of the nervous system. It is a part of the lateral indirect extrapyramidal tract.

It is rudimentary and functionally less important in humans. It is involved in motor control of distal flexors of the upper limb - especially of the hand and fingers - by promoting flexor tone while inhibiting extensors. It complements the lateral corticospinal tract.

Anatomy
The rubrospinal tract originates in the magnocellular red nucleus in the caudal part of the red nucleus of the midbrain. It decussates (crosses over) within the anterior tegmentum of the midbrain. In the pons, it is situated medially within the rostral pontine tegmentum. In the medulla oblongata, it descends within the lateral tegmentum medial to the spinocerebellar tract, and posterior to the spinothalamic tract. In the spinal cord, it descends in the lateral funiculus, adjacent to the lateral corticospinal tract. It terminates in the contralateral cervical spinal cord by synapsing with interneurons of the lateral intermediate zone and anterior horn of the spinal cord.

Function
In humans, the rubrospinal tract is one of several major motor control pathways. It is smaller and has fewer axons than the corticospinal tract, suggesting that it is less important in motor control. It is one of the pathways for the mediation of involuntary movement, along with other extra-pyramidal tracts including the vestibulospinal, tectospinal, and reticulospinal tracts. The tract is responsible for large muscle movement regulation flexor and inhibiting extensor tone as well as fine motor control. It terminates primarily in the cervical and thoracic portions of the spinal cord, suggesting that it functions in upper limb but not in lower limb control.

It is small and rudimentary in humans. In some other primates, however, experiments have shown that over time, the rubrospinal tract can assume almost all the duties of the corticospinal tract when the corticospinal tract is lesioned.