How pheromones work by James V. Kohl

The response to pheromones, is a “survival of the species” concept that has been repeatedly detailed in examples of classical conditioning. In more evolved species like mammals, classical conditioning of the response to pheromones involves at least one other sensory stimulus from the social environment (e.g., an environment that includes other members of the same species).

In classical conditioning, one sensory stimulus is repeatedly paired with another sensory stimulus. This repeated pairing allows the second sensory stimulus to cause the same behavioral response that was initially caused by the first. In fact, after the response is conditioned to occur, the second sensory stimulus can then cause the same behavioral response even in the absence of the first stimulus. For example, after visual input is paired with the effect of pheromones on hormones and behavior, what we see can cause us to respond as if the pheromones were causing changes in the hormones that affect our behavior. (more…)

Sold on the human VNO?

Recent discoveries show that human pheromones are signals that are processed by cells in our main olfactory system. http://www.ncbi.nlm.nih.gov/pubmed/17917120

Accordingly, as they do in all other mammals, pheromones activate the hypothalamus in humans. http://www.ncbi.nlm.nih.gov/pubmed/19235878

Human pheromones cause behavior to change via their effects on hormones secreted by the hypothalamus. http://senseofsmell.org/papers/Human_Pheromones_Final%207-15-09.pdf

Though it is widely reported to exist, the adult human vomeronasal organ (VNO) is not functional. http://www.ncbi.nlm.nih.gov/pubmed/10531049; http://www.ncbi.nlm.nih.gov/pubmed/11369678; http://www.ncbi.nlm.nih.gov/pubmed/15470677

It contains few nerve cells and consists largely of epithelial cells, which means it has no sensory function. http://www.ncbi.nlm.nih.gov/pubmed/4068105

Most cells of the adult human VNO express the protein markers of skin cells, not nerve cells. No cells have synaptic contacts, and there is no evidence that any nerve connects with the human VNO. http://www.ncbi.nlm.nih.gov/pubmed/10944499; http://www.ncbi.nlm.nih.gov/pubmed/12107500

Finally, no cells express the protein that is the primary indicator of mature olfactory nerve cells. http://www.ncbi.nlm.nih.gov/pubmed/336785

If you think you’ve found scientific support for misleading claims about a functional human VNO, look further and see what other researchers say in the links to the articles above.

These next few links are to articles that focus on research that apparently is supported by a woman who claims to be the co-discoverer of human pheromones based on the acclamations of television.

http://www.ncbi.nlm.nih.gov/pubmed/9883309 comment on http://www.ncbi.nlm.nih.gov/pubmed/9494686. http://www.ncbi.nlm.nih.gov/pubmed/15327919 comment on http://www.ncbi.nlm.nih.gov/pubmed/11897264, and on http://www.ncbi.nlm.nih.gov/pubmed/9494686.

Effects of pheromones attributed to touch (in mice)

Paternal mice bond with their offspring through the power of touch Prior work (1) from two of these same authors correctly attributed changes in the production of new brain cells to the effect of pheromones on  neurons in the olfactory bulb that express gonadotropin-releasing hormone (GnRH), which send projections to the hypothalamus. This results in the release of luteinizing hormone and follicular-stimulating hormone (FSH) by the anterior pituitary.  Together, LH and FSH control the release of steroid hormones, such as estrogen, that influence sexual behavior via effects on neurogenesis. Estrogen promotes the release of prolactin (PRL) and provides a regulatory feedback loop for LH and FSH release.

Looking at the downstream effects of GnRH on other hormones, and then attributing effects on neurogenesis and behavior to these other hormones derails the logic of an well-established link from pheromones to behavior.

In the report linked above, the effect of pheromones is attributed to touch. Clearly, however, it is the effect of pheromones that stimulates the production of new brain cells, as has been detailed in other works, including at least one by Dr. Weiss and his colleagues.

(1) http://www.ncbi.nlm.nih.gov/pubmed/17603480, also see the story at http://www.medicalnewstoday.com/articles/75900.php “Weiss said “We found that pheromones, and particularly dominant male pheromones, can stimulate the production of new brain cells,…”