'Nerve Zero' and Speculation on Human Happiness

R. Douglas Fields. the neuro- and cognitive scientist, wrote a curious and very cautious account of a cranial nerve in the sperm whale in Scientific American some four or five years ago which, true or not, gave rise to some thoughts on our perception of reality.  He has postulated that this Nerve Zero is an additional 'sense' and that it might be operative as such in the human being, given common mammalian structures.

Whether his thesis will be confirmed or not, Fields is dealing with a mystery - whether a tiny nerve, hitherto ignored, at the base of the brain, is at the heart of subliminal sexual attraction. Do pheromones hit this nerve and relay deep subsconscious signals to the brain? Does this explain 'instant attraction' and what does it mean for sexual free will?

Most nerves enter the brain through the spinal chord but cranial nerves go direct to the brain and so to the 'mind'. They are linked to our sensory inputs and to the way we express ourselves, so a 'sixth' sense linked to a cranial nerve looks to be intimately connected to the way we construct our reality and the way that we behave.

Such a nerve is a part not of the autonomic process or of our willed movement (though we can will much of our expression) so much as of the system by which sensory inputs compete for attention and so create our model of the world - if the nerve exists quite as Fields suggests. It may also have (see below) an expressive component of its own.

The nerve itself provenly exists in all vertebrates (discovered in humans as long ago as 1913) but what exactly it is for is what remains disputed. What we do know is that it sends its endings to the nose which has led some sceptics to believe that it is merely a frayed strand of the olfactory nerve. Field's whale autopsy threw that thesis in doubt.

The role of the olfactory nerve with its complex of 347 types of receptor cell in determining sex, social rank, territories, reproductive status and even the identity of individuals such as mates and offspring is well accepted and there are certainly indications that humans, like other animals, exchange secret pheromone messages.

Pheromones are, according to Fields and others, very different from odor-producing molecules. Pheromones are large molecules that need intimate contact to pass between persons (such as kissing or 'snuggling'), whereas smells are small and volatile molecules that can travel large distances. Pheromones also do not need to 'smell' - if a pheromone goes straight to our brain, it could by-pass our consciousness entirely so the issue is only whether there is a mechanism for doing this. So-called 'nerve zero' allows the possibility of that by-pass.

There is a pheronome detector in the animal brain as it is - a specialised area within the vomeronasal organ which connects to the olfactory bulb in the brain that sorts and makes sense of olfactory inputs but which then routes these to the amygdala (sexual arousal through release of hormones) rather than the olfactory cortex (conscious perception). Pheromones (it is believed) can influence the oestrus cycle, stimulate sexual behaviour and ovulation and even, when it goes wrong, cause abortion. Pheromones from familiar and unfamilar mates can have different effects in this respect.

In 2006, Buck and Liberles (one of whom is a Nobel Laureate) found a new family of receptor proteins [TAARS] on the mouse nose, on the surface of the sense cells that detect pheromones. This, we are told, increases the possibility that mammals, at least, have a separate pheromone pathway. Certainly the mouse pheromones are intimately linked to sexual behaviours. Buck found that humans have the genes to make at least six of the 15 pheromone receptors found in the mice. However, the human vomeronasal organ appears to be vestigial, like gill slits, in humans so if pheromones are travelling to the human brain it is not by that route.

This is where 'nerve zero' may be relevant - its endings are in the nasal cavity (the 'pick up' point) and its nerve fibers reach into those ''hot-button' [Fields again] sex regions of the brain that are concerned with basic reproduction, that release sex hormones and control thirst and hunger, completely by-passing the conssciousness-creating olfactory bulb. The sort of cruel experimentation done by scientists to extend our knowledge - the 'original sin' behind all knowing in this area - has shown that severing 'nerve zero' in hamsters results in a failure to mate. Electrically stimulating the nerve in fish and other animals seems to be related to the triggering of sexual responses. The evidence mounts.

Other research by Fields suggests that nerve zero fibres were stuffed with peptide hormones that led him to conclude that the nerve could even be a neurosecretory organ in its own right, regulating reproduction by releasing hormones. But nerve zero remains a mystery. It is doing something different from analysing smell and it connects to the part of the brain controlling reproduction whilst also releasing a powerful sex hormone into the blood. If its early embryonic pathway is disturbed, the result is a syndrome that leaves the animal unable to mature sexually beyond puberty.

Nor need nerve zero have a solely sexual function since electrical impulses are travelling out from the brain through the nerve with no current understanding of their function, leaving room for some interesting and wholly unscientific speculation about our ability to communicate intimacy beyond immediate consciousness ... could this be love? Fields raises the old free will problem since, if he is right, external stimuli are by-passing consciousness in order to control brain and behaviour.

Psychological experiments seem to indicate that cognitive abilities improve when people smell the sweat of fearful rather than happy people so that the psychological state of one person seems to be able to trigger the cognitive state of another if they are within 'smell' distance. Socially, this suggests that groups can operate at some level like flocks or herds, certainly in states of excitation or danger. Chemical warning signals may be being transferred from person to person at a level well below the consciousness of each.

Women with more pheromone release around their nipples tend to get their children to latch on and gain weight faster than women without such glands - another intriguing example of an instinctive biological operation beyond consciousness. But there is another aspect to the case. It is pretty well established that the mind is selective in choosing inputs from the five senses so that the picture of the world on which we operate is a representation of it but it is not the only possible representation and it is a representation that deliberately excludes large tracts of objective reality in order to allow us to function.

As we have noted in earlier essays, our social reality is a compromise between millions of individual realities where the socialised mind of each individual helps in choosing between sensory inputs, prioritising the inputs into a mental map that starts on the basis of 'prejudice'. To de-socialise the mental map is to re-see the territory. Now we have a sixth instinctual sense to cope with, one that adds intimacy and sexuality to the socialised mind either to subvert it perhaps or to direct it to its own instinctual nature regardless of social norms. This instinct is animal and personal, based on intimate communications with very significant others and on a guardedness about the world beyond.

Universalists and rationalists will hate this. Perhaps they would want this nerve removed. But it is an essential part of who we are and socialisation and failed attempts at 'perfectability' flounder, to our great individual benefit, on the subversion offered by our instinctive desires and our need to flock with those we feel comfortable with. The pheromonal nerve zero may not only mean that love is blind and 'against reason' (which we knew) but that pheromonality represents some higher reason where the mind-body that is more than ego-consciousness is seeking out what is best for it in a world where 'all things are equal'.

Of course, social norms and culture do not permit 'all things to be equal' (this is classic 'alienation' territory) so perhaps this is the dilemma - to have a culture where 'nerve zero' constantly fights for happiness against the acculturation process or one that is adapted to 'nerve zero' and is, thus, happy. Such an integrated culture could be a revolutionary one.