Brain circuits that modulate sociability.

The social bonding neuropeptide oxytocin can be traced over 500 million years, with analogous peptides found in birds, reptiles, fish, amphibians, and some invertebrates. Hung et al. have found that release of oxytocin in the ventral tegmental area of the brain increases prosocial behaviors in mice. Optogenetic manipulation of oxytocin release influences sociability in a context-dependent manner. Oxytocin increases activity in dopamine cells that project to the nucleus accumbens, another key node of reward circuitry in the brain. Here is their abstract, followed by a nice graphic of the relevant systems in the human brain.

The reward generated by social interactions is critical for promoting prosocial behaviors. Here we present evidence that oxytocin (OXT) release in the ventral tegmental area (VTA), a key node of the brain’s reward circuitry, is necessary to elicit social reward. During social interactions, activity in paraventricular nucleus (PVN) OXT neurons increased. Direct activation of these neurons in the PVN or their terminals in the VTA enhanced prosocial behaviors. Conversely, inhibition of PVN OXT axon terminals in the VTA decreased social interactions. OXT increased excitatory drive onto reward-specific VTA dopamine (DA) neurons. These results demonstrate that OXT promotes prosocial behavior through direct effects on VTA DA neurons, thus providing mechanistic insight into how social interactions can generate rewarding experiences.