The descending fibers of this tract arise in the interstitial nucleus of Cajal (an accessory nucleus of III) in the tegmentum of the midbrain. They descend ipsilaterally only to the cervical level of the cord, where they synapse in laminae VI, VII, and VIII. The tract may play a role in reflex movements of the head and neck in response to visual stimuli, but its function is largely unknown and probably more complex.