- The Fove Theory part #25
“Sexual attraction and the selective social attachments that often follow are two of the most powerful driving forces of human behavior, profoundly influencing art, music, literature, and politics throughout history. The presence of strong, enduring relationships between sexual partners is widespread in nearly all societies, particularly in societies where monogamy is a predominant feature of the social organization. Whether humans have a biological propensity to practice monogamy (or perhaps more correctly, serial monogamy) is debatable; however, there is little doubt that the ability to form intense social attachments – or pair bonds – with a mate has a biological architecture with definable molecular and neural mechanisms.” (Larry Young & Zuoxin Wang, The neurobiology of pair bonding, Nature Neuroscience 7:1048-1054, 2004)
The Exciting Circuitry of Pair Bonding (a model)
Larry Young is one of the world’s leading experts in the field of social behavioral neuroscience and chief of the Division of Behavioral Neuroscience and Psychiatric Disorders at the Yerkes National Primate Research Center, a controversial but important multidisciplinary biomedical research center in Atlanta, Georgia (USA). In 2009, Yerkes researchers had successfully injected a single-cell prairie vole embryo with a lentivirus containing a gene found in glowing jellyfish, thus generating the very first transgenic prairie vole. Lentiviral gene transfer is one of the current techniques for genetic modification of laboratory animals used for the evaluation of efficacy and safety of new drugs or therapeutic concepts. Despite the controversy, these methods are absolutely fundamental to biomedical research in areas such as neurodegenerative diseases (Alzheimer’s, Parkinson’s, or Huntington’s disease) or diabetes mellitus. For Young and his team, the transgenic prairie voles are an important step toward unlocking the genetic and neurobiological mechanisms that underlie social bonding and social attachment and will promote discovery and knowledge on the social brain to determine whether monogamy and its associated social behaviors can be affected by manipulating a single gene, to better understand the depressive states of the mind that arise from the loss of a child or unwanted break-up, or develop novel strategies for treating social deficits in the autism spectrum disorders.
Understanding the molecular and neural mechanisms of love is a direct consequence of the interpretation of that knowledge, which is something that scientists do naturally; we
overthink and give an interpretation to the things happening around us.
Across species, the ability to recognize a familiar individual forms the primary foundation upon which all social relationships (of kinship, friendship, courtship, loveship, hateship – not necessarily in this order –) are built. In complex social systems, it is therefore mandatory to encode and recall not only general characteristics about other individuals, such as gender, but also very specific, individual details of social status or consanguinity. And because humans encode and recall these characteristics unconsciously, one of the strategies wittingly used in the unattached, one-night-stand sex to prevent the development of a social relationship (of any kind) is to keep the unknown unknown. Of course, in response, one could unintentionally be so good they cannot ignore him/her, therefore bypassing such stubborn lack of interest… or intentionally force the tight-lipped strategist(s?) not only to successfully encode and recall one’s name but also spell it, in Italian. And backwards. After this neurological trick, no one can ever forget you.
The monogamous prairie vole has proven to be a useful model for elucidating the neural substrates of pair bond formation. Such model suggests that three separate, yet interconnected, neural circuits converge in the nucleus accumbens to yield the development of the pair bond. A peptidergic pathway involved in the processing of social cues and formation of social memories is tightly coupled with a dopaminergic reward circuitry; given that during mating these two circuits are modulated by ascending circuits conveying somatosensory information, some researchers have hypothesized that pair bonding may be the result of a conditioned reward learning, in which a powerful association forms between the reinforcing properties of sex (unconditional stimulus) and the specific olfactory signature of the partner (conditioned stimulus), similar to the neural processes that establish drug-induced place preferences in humans. Due to the low densities of oxytocin and vasopressin subtype 1a receptors in the peptidergic pathway in nonmonogamous species, the peptidergic pathway, which promotes pair bonding through the release of oxytocin and vasopressin within the brain, and the dopaminergic reward circuitry, which promotes reward (and reinforcement) through the release of dopamine, would be uncoupled and thus result in the failure to form pair bonds.
Nonetheless, humans failed to have a natural tendency to vigorously investigate a novel individual and encode social cues via olfactory signals. This makes such pair bonding model useful to understand the mechanisms that underlie pair bonding on rodents, yet hardly applicable to humans. In humans, a direct individual recognition relies mostly on visual and auditory signatures (putatively, the conditioned stimulus) associated with the most mind-blowing and reinforcing memories of sex (putatively, the unconditioned stimulus) that the highly sophisticated hippocampus (brain’s memory center) would ensure to link to the right person. Whether or not centrally released oxytocin and vasopressin massage our expectations to favor a specific individual is still to be proven and thus remains speculative. What cannot be ignored is the emergence of the neocortex and its ability to modify subcortical function and that, despite the fact that some people might fall in (romantic) love in the absence of sex, I do not know any. No theory can also ignore the fact that prairie voles did not experience in their translucent shoe-size boxes any of the life-changing events that had been changing the way we communicate, interact, and ultimately attach to each other which, for the sake of clarity, are often whisked away from attachment models. Therefore, in order to understand the neural circuitry of human love in the XXI century, some basic knowledge in the neuroscience of pair bonding is essential but a more realistic approach is mandatory.