The Reticular formation is a rod-shaped brainstem structure associated with the upper motor system and involved with movement.
It serves as the intermediary in an indirect projection between cortical areas associated with movement (primary motor cortex and premotor cortex) and medial regions of the spinal cord. Axon tracts running from the associated motor regions bifurcate into two individual axon tracts before reaching the reticular formation in the dorsal region of the brainstem. There are two reticular formations of the body, and motor cortices on one bilateral half of the brain can innervate both.
One tract innerves the ipsalateral reticular formation, and one side innervates the contralateral reticular formation. The reticular formations at their ends project further axonal bundles. The ipsalateral reticular formation sends one bundle to the ipsalateral medial segments of the spinal cord while the contralateral reticular formation sends one bundle to the contralateral medial segments of the spinal cord. When the bundles terminate, they innervate both sides of the spinal cord, although they are colocalized to the medial areas.
The reticular formation's projections are part of the corticoreticulospinal tract.