Why Do Birds Flock? A Role for Opioids in the Reinforcement of Gregarious Social Interactions

Conclusion We propose that studies of songbirds reveal a novel network model for the integration of positive and negative reinforcement processes in non-sexual affiliative social behavior. Most studies on affiliative behavior focus on the positive affective state induced by social contact that rewards individuals interacting together. However, this review highlights that in social animals, affiliative contact is also reinforced because it reduces a negative affective state caused by social exclusion or isolation, thus creating a complementary system (i.e., positive reinforcement from affiliative interactions and negative reinforcement from termination of isolation). In this review we build the case that both of these mechanisms are central to flock formation and maintenance and propose that mu opioid receptor activity in the mPOA may modulate a positive state induced by flocking, via a projection to VTA, and may reduce a negative affective state resulting from social separation, via a projection to PAG. Neural systems that underlie important social behaviors are evolutionarily conserved (Panksepp, 2005, 2016; O’Connell and Hofmann, 2011). This suggests that a molecular/genetic substrate that existed in a common ancestor has been conserved to provide a foundation for the generation of novel social behaviors across vertebrates, and to fine-tune social behaviors to match the ecological needs of individual species. Thus studies of songbird flocking may advance the underst...
Source: Frontiers in Physiology - Category: Physiology Source Type: research