In this video I discuss the corticospinal tract, a major tract that carries movement-related information from the motor cortex to the spinal cord. I discuss upper and lower motor neurons and trace the pathway the corticospinal tract takes from the cortex to the spinal cord, mentioning the major fiber bundles it is found in along the way like the cerebral peduncles and medullary pyramids. I describe the two branches of the corticospinal tract: the lateral and anterior corticospinal tracts, and I discuss their respective specializations. Finally, I cover the types of deficits that can appear when damage to the corticospinal tract occurs.
For an article (on my website) that explains the corticospinal tract more in-depth, click this link:
https://neuroscientificallychallenged.com/posts/know-your-brain-corticospinal-tract
TRANSCRIPT:
Welcome to 2 minute neuroscience, where I simplistically explain neuroscience topics in 2 minutes or less. In this installment I will discuss the corticospinal tract.
The corticospinal tract is a major tract that carries movement-related information from the motor cortex to the spinal cord. The neurons that travel in the corticospinal tract are called upper motor neurons; they form connections with neurons called lower motor neurons, which carry movement-related impulses to muscle itself, causing it to contract.
The upper motor neurons of the corticospinal tract leave the motor cortex and descend to the brainstem, entering the midbrain in large fiber bundles called the cerebral peduncles. The tract continues down into the medulla where the fibers form two bundles, known as the pyramids, which create visible ridges on the exterior surface of the brainstem. At the base of the pyramids, about 90% of the fibers in the corticospinal tract decussate, or cross to the other side of the brainstem in a bundle called the pyramidal decussation. The decussating fibers will then enter the spinal cord on the opposite side of the body from where they originated as part of the lateral corticospinal tract. The other 10% of the fibers will continue into the spinal cord on the same side of the body where they originated as part of the ventral or anterior corticospinal tract and only cross over when they reach the level of the spinal cord where they will synapse on a lower motor neuron. It is thought that the lateral and anterior corticospinal tract fibers have slightly different specializations, with the lateral corticospinal tract controlling the movement of more distal muscles like those of the hands, and the anterior corticospinal tract controlling the movement of more proximal muscles like those of the trunk.
Damage to the corticospinal tract can lead to a collection of symptoms known as upper motor neuron syndrome, which involves symptoms like weakness or paralysis, hyperactive reflexes, decreased motor control, and either increased or decreased muscle tone. Over time patients may regain the ability to make crude movements but fine finger movements like writing or typing may remain impaired, suggesting the corticospinal tract is especially important for these types of movements.
REFERENCE:
Nolte J. The Human Brain: An Introduction to its Functional Anatomy. 6th ed. Philadelphia, PA. Elsevier; 2009.
