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Rewarding Nature of Social Contact
Science 29 Sep 2017: Vol. 357, Issue 6358, pp. 1353-1354 The rewarding nature of social contact Stephanie D. Preston Department of Psychology, University of Michigan, Ann Arbor, MI, USA. [paraphrase] The fundamental components of most human traits are shared by other species, in both form and function, indicating a common ancestor and an evolution over time. For example, humans, monkeys, rodents, sheep, and dogs all share mechanisms for bonding with mates or for protecting newborn kin—processes that support acts of kindness. Indeed, the famous social bonding neuropeptide oxytocin can be traced over 500 million years, with analogous peptides found in birds, reptiles, fish, amphibians, and some invertebrates. Converging research on the role of oxytocin in social bonding suggests that approaching others becomes less scary and more rewarding when it is valuable to the individual. In the brain, oxytocin is secreted by the paraventricular nucleus (PVN) of the hypothalamus and projects to regions that are rich with oxytocin receptors, including those associated with dopaminergic reward-based motivation [e.g., ventral tegmental area (VTA) and nucleus accumbens (NAcc) in the mesolimbocortical system]. For example, the density of oxytocin receptors in the NAcc is higher in monogamous than nonmonogamous voles, and the monogamous bond is prevented if oxytocin receptors are blocked or NAcc dopamine is antagonized. Oxytocin also facilitates the motivation to approach newborn pups through connections to the dopaminergic VTA. For bonded mates and offspring, oxytocin facilitates approach while helping to establish the memory of the partner and reinforcing the bond. Because the dopaminergic reward system is also linked to motivation for hedonic pleasures and reinforcement (including drugs, sexual experiences, chocolate, goods, and attractive faces), it has been assumed that oxytocin facilitates social bonds by rendering another individual like a drug—something to approach, enjoy, remember, and seek again. Link to — Diagram of Gating of Social Reward by Oxytocin in the Ventral Tegmental Area Link to — Gating of Social Reward by Oxytocin in the Ventral Tegmental Area Photostimulating PVN oxytocin neurons could not itself reinforce a preference for an empty chamber or reinforce a nonsocial nose-poke behavior; this indicates that the oxytocin release itself is not pleasurable. Researchers found increased spontaneous cell firing in NAcc-projecting VTA dopamine neurons after applying an oxytocin receptor agonist. Hung et al. concluded that oxytocin release in the VTA from the PVN is linked, at the time of a new social interaction, to increased excitability of dopamine neurons that project to the NAcc, releasing dopamine in the NAcc and, thereby, reinforcing the social interaction. [end of paraphrase]
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