Cranial nerve XIII (sometimes named cranial nerve 0, zero nerve or nerve N)
This nerve, commonly referred to as the terminal nerve, is a highly conserved multifaceted nerve found just above the olfactory bulbs in humans and most vertebrate species.
In most forms its fibers course from the rostral portion of the brain to the olfactory and nasal epithelia.
The terminal nerve is one of the three most rostral cranial nerves and is characterized by neurons that contain gonadotropin releasing-hormone (GnRH).
While its modality is not yet completely understood, it may play a role in reproductive behavior.
Although very close to the olfactory nerve, the terminal nerve is not connected to the olfactory bulb, where smells are analyzed.
This fact suggests that the nerve is either vestigial or may be related to the sensing of pheromones.