Our group is interested in understanding how the brain processes the distress and pain of others, why we experience empathy for some but not other individuals or groups, and how the decision to approach and help someone in need is computed. Using an integrative approach that combines behavior, immunostaining and optogenetic tools, our lab examines the brain’s response at the cell and circuit level, to outline the molecular pathway involved in pro-social responses. Our research seeks to inform basic understanding of the mechanism underlying social behavior and provides a translational path for interventions targeted at psychopathologies and trauma victims involving empathy deficits.
This manuscript, published in eLife 2014, found that rats have an ingroup bias for helping, and will only help ingroup members (familiar and stranger rats of their own strain). Rats do not release outgroup members (rats of an unfamiliar strain). Encouragingly, this bias is very flexible and can be completely abolished by two weeks of co-housing with a member of the outgroup.
The biology of empathy
Empathy, the recognition and sharing of emotional states between individuals, is a powerful motivator of pro-social behavior. The field of social neuroscience has been shedding light on the biological mechanisms that drive the empathic experience. In humans, empathy for the pain of others is correlated with activation of a shared neural network for processing the pain for self and other. This network, refered to as the affective pain matrix, includes areas in the limbic system as well as the Anterior Cingulate Cortex, the Insula, and frontal areas. These circuits interact with hormones related to social behavior such as oxytocin and vassopressin, and the HPA axis to generate the empathic experience. These systems act together to generate an aversive response to the distress of others, and can motivate the observer to help the other in need.
The Helping Behavior Test
The helping behavior test shows that rats will try to release a cagemate trapped inside a restrainer, and once they learn how to do so, will repeat the behavior intentionally and consistently on subsequent testing sessions. During testing, a rat (free rat) is placed in an arena containing another rat trapped inside a plexiglass restrainer. The restrainer has a door that can only be opened from the outside, by the free rat. The rats are tested over 12 sessions of 1 hour each. The free rat is able to perceive the distress of the trapped rat and approaches the restrainer. It takes rats about 5 days to learn to open the restrainer, and once they learn, rats will continue releasing the trapped rat on following days. Rats are as motivated to release cagemates as they are to access chocolate, and they often share their chocolate with the trapped rat.
The evolution of pro-sociality
Pro-social behavior is found across multiple species in nature. From ants and fish to birds, behavior that benefits others is a widely observed phenomenon. Helping behavior is beneficial for group survival, and is essential in promoting cooperation and reducing aggression within the group. In humans, helping is often motivated by empathic concern. Empathy is thought to have first evolved in the context of maternal care,with the imperative of responding to the offspring's needs. Empathy was further expanded to the extended social environment. Empathy in humans is based on neural structures which are highly conserved across mammalian species, and utilizes endocrine and autonomic systems that are found in many species.