Several tests have been conducted to provide evidence that Cranial Nerve Zero is responsible for our responses to pheromones. The 13th cranial nerve known by the name Nervus terminalis or Terminal nerve is most often destroyed during dissection procedure making it unavailable to our sense of vision. This made the existence of Cranial Nerve Zero disputed and we don’t see this in our medical textbooks till date. Cranial Nerve Zero was first discovered by German Scientist Gustav Fritsch in 1878 in brain of sharks. After that scientists found this nerve in whales. Whales are such animals which through evolution have lost their olfactory cranial nerves. This supported the idea Cranial Nerve Zero is separate from olfactory system. More importantly it underlined an evolutionary importance of Nervus terminalis.
It was first found in humans in 1913. Initially it was confused to be associated with olfactory nerves i.e. extra lobular olfactory projections. After further investigations, it was found that cranial nerve zero is not connected to the olfactory bulb. The nerve projects to medial and lateral septic nuclei and preoptic areas which are involved in sexual behavior of animals. Based upon study approaches used to study structure and incidence of the nerve like dissection microscopy, light microscopy, transmission electron microscopy and immunohistochemistry, it has been concluded that terminal nerve is a common finding in adult human brain.
The Nervus terminalis lies bilaterally as a plexus of unmyelinated peripheral nerve fascicles in subarachnoid space covering gyrus rectus of orbital surface of frontal lobe. The plexus in the region of cribiform plate of ethmoid courses posteriorly to vicinity of olfactory trigone, medial olfactory region and lamina terminalis. As compared to human adults, it is very prominent in infants and fetuses.
Several studies in cell and molecular biology have demonstrated the significant role of Nervus terminalis in the release of luteinizing releasing luteinizing hormone (LHRH) and is therefore thought to play role in reproductive behavior. One of the such studies in July 2012 suggests that functional evidence of Cranial Nerve Zero is sufficient enough to make it a part of medical school curriculum and Neuroanatomy Texbooks.