The article I mentioned here on 3/12/12 is in the news, again.
Excerpt: “Love and sexual desire activate different areas of the striatum. The area activated by sexual desire is usually activated by things that are inherently pleasurable, such as sex or food. The area activated by love is involved in the process of conditioning by which things paired with reward or pleasure are given inherent value. That is, as feelings of sexual desire develop into love, they are processed in a different place in the striatum.”
My comment: An animal model is missing from this representation of how the conditioning of sexual desire develops into love. For example, model organisms are typically used to link “…things that are inherently pleasurable, such as sex or food…” to the development of pathways in the brain. These researchers claim that a pathway links love and sexual desire. Where’s the animal model or model organism for that?
Here it is! Pfaus et al., (2012) details how odors are responsible for sexual reward and bonding, which seem to merge in conscious awareness under the right circumstances (e.g., in humans) as romantic love. But the representation in Cacioppo et al, (2012) is one where viewing erotic pictures or looking at photographs of their significant others was used to form a complete map of love and desire in the brain. Are odors responsible for love and desire, or is it what we see?
A complete map of love and desire in the brain must have its basis in what is currently known about the molecular biology of brain development. Fortunately, there’s an animal model for that. For example, the neuroanatomist, Simon LeVay writes: “This model is attractive in that it solves the “binding problem” of sexual attraction. By that I mean the problem of why all the different features of men or women (visual appearance and feel of face, body, and genitals; voice quality, smell; personality and behavior, etc.) attract people as a more or less coherent package representing one sex, rather than as an arbitrary collage of male and female characteristics. If all these characteristics come to be attractive because they were experienced in association with a male- or female-specific pheromone, then they will naturally go together even in the absence of complex genetically coded instructions (LeVay, 2011, p. 210).”
I’ve taken this model of olfactory/pheromonal conditioning (Kohl, 2007), which LeVay summarized, even further in accord with the role of odors and rewards, which is consistent with Pfaus et al., (2012), but not consistent with the representation in Cacioppo et al, (2012). In “Human pheromones and food odors: epigenetic influences on the socioaffective nature of evolved behaviors” (Kohl, 2012), I detailed how the molecular biology that’s common to species from microbes to man allows nutrient chemicals and pheromones to influence reward-driven behavior in all species.
Unfortunately, there is no love in this model. But, if there were, it would be both the love of food and the love of other people. All reward mechanisms in my model are directly linked to behavior from the epigenetic effects of nutrient chemicals manifested in food odors, and the animal ‘chemistry’ of attraction manifested in pheromones. It’s food odors and pheromones that are responsible for our inherently pleasurable experiences with food or sex. Erotic imagery or looking at photographs cannot be used to map love and desire in the brain any more than a picture of food could be used to map the desire to eat or the ‘love’ of food. Showing how the brain lights up, does not show anything about the biology of cause and effect. (The end does not necessarily show the means.)
The map that’s required is one that must be based on what’s already known, which is that olfaction and odor receptors provide a clear evolutionary trail that can be followed from unicellular organisms to insects to humans. That map requires details of the neurophysiological mechanisms required to link sensory input from the environment directly to epigenetic effects on hormones that affect behavior.
If you want to know where love is, you can find out by following the path from your nose to the brain via the epigenetic effects of food odors and pheromones on hormone-secreting nerve cells, not one that somehow links pictures to love and sexual desire. There’s no model for that!
Cacioppo, S., Bianchi-Demicheli, F., Frum, C., Pfaus, J. G., & Lewis, J. W. (2012). The Common Neural Bases Between Sexual Desire and Love: A Multilevel Kernel Density fMRI Analysis. J Sex Med, 9(4), 1048–1054.
Kohl, J. V. (2007). The Mind’s Eyes: Human pheromones, neuroscience, and male sexual preferences. In M. R. Kauth (Ed.), Handbook of the Evolution of Human Sexuality (pp. 313-369). Binghamton: Haworth Press.
Kohl, J. V. (2012). Human pheromones and food odors: epigenetic influences on the socioaffective nature of evolved behaviors. Socioaffective Neuroscience & Psychology, 2, 17338 – DOI: 17310.13402/snp.v17332i17330.17338.
LeVay, S. (2011). Gay, Straight, and the Reason Why: The Science of Sexual Orientation: Oxford University Press.
Pfaus, J., Kippin, T., Coria-Avila, G., Gelez, H., Afonso, V., Ismail, N., et al. (2012). Who, What, Where, When (and Maybe Even Why)? How the Experience of Sexual Reward Connects Sexual Desire, Preference, and Performance. Archives of Sexual Behavior, 41(1), 31-62.