They are found in the cerebral cortex and brainstem and carry information down to activate interneurons and lower motor neurons, which in turn directly signal muscles to contract or relax.

The axons of the upper motor neurons project out of the precentral gyrus travelling through to the brainstem, where they will decussate (intersect) within the lower medulla oblongata to form the lateral corticospinal tract on each side of the spinal cord.

The fibers that do not decussate will pass through the medulla and continue on to form the anterior corticospinal tracts.

Upper motor neurons travel in several neural pathways through the central nervous system (CNS): Any upper motor neuron lesion, also known as pyramidal insufficiency, occurs in the neural pathway above the anterior horn of the spinal cord.

The resulting changes in muscle performance that can be wide and varied are described overall as upper motor neuron syndrome.