Descending Spinal Tracts
- The lateral pathways are involved in voluntary movement of the distal musculature and are
under direct cortical control. The consist of:
o Corticospinal Tracts
o Rubrospinal Tracts
- The ventromedial pathways are involved in the control of posture and locomotion and are under
brain stem control. They consist of:
o Reticulospinal tract (medullary and pontine)
o Vestibulospinal tract
o Tectospinal tract
The Lateral Pathways
- Corticospinal tract is the most important component, originating in the neocortex (motor and
- Its axons pass through the internal capsule briding the telecephalon and thalamus -> base of
cerebral peduncle -> pons -> collect at the medullary pyramid.
o Also called the pyramidal tract.
- At the junction of medulla and spinal cord, the pyramidal tract decussates, and collect in the
lateral column of the spinal cord and form the lateral corticospinal tract that terminate in the
dorsolateral region of the ventral horns.
- Rubrospinal Tract is a smaller component of the lateral pathways originating in the red nucleus
of the midbrain. Its axons decussate in the pons and join those in the corticospinal tract in the
lateral column of the spinal cord.
- A major source of input to the red nucleus is the same region in the frontal cortex that also
contributes to the corticospinal tract.
- Lesions in the corticospinal tract alone caused a movement deficit as severe as that observed
after lesions in the lateral columns, but many functions gradually reappear as the rubrospinal
tract takes over. Another lesion here would reverse the recovery showing that the corticospinal
pathway was able to partially compensate for the loss of the corticospinal tract input.
The ventromedial pathways
- Contains four descending tracts that originate in the brain stem that use sensory information
about balance, body position, and the visual environment to reflexively maintain balance and
o vestibulospinal tract
o tectospinal tract
o pontine reticulospinal tract
o medullary reticulospinal tract - The vestibulospinal and the tectospinal tracts function to keep the head balanced o