Corticospinal tract

Tract

Function

Origin

Crossed

Termination

Corticospinal

Voluntary (skilled) movement

Motor (some sensory) cerebral cortex

Majority cross (lateral corticospinal tract) as pyramidal decussation (in medulla)

Intermediate gray and ventral horn

Feature

Conveys voluntary skilled movements Fibers originate from:
- Betz cells: 3% of fibers in layer 5 of the motor cortex
- Area 4: 30% of fibers
- Premotor area 6: 30% of fibers
- Postcentral areas 3, 1, and 2 and parietal (area 5) cortex, 40% of these fibers from the parietal lobe
Fibers go through the pyramid (60% myelinated) to the spinomedullary junction:
- Lateral corticospinal tract — 90% of the fibers, almost all are crossed, travel in the posterolateral funiculus, and enter the intermediate gray to laminas IV, V, VI, and VII. A few go to anterior horns in lamina IX.
- Anterior corticospinal tract — 10% of the fibers, ipsilateral but cross in the anterior white commissure to enter lamina VII.
- Anterolateral corticospinal tract — ipsilateral, to the posterior horn and intermediate gray
Neurotransmitters — glutamate and aspartate

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