Empathic helping in rats and its modulation by social parameters

Empathy, the recognition and sharing of affective states between individuals, is an adaptive response with ancient evolutionary roots. The experience of empathy rises from activation of subcortical neural circuits in the brain stem, thalamus and paralimbic areas that are highly conserved across mammalian species. Primarily, it is crucial for the survival of altricial mammals to be able to respond to the needs of offspring appropriately. More broadly, communication of emotions promotes group survival, by alerting against potential threats and, depending on context, inducing pro-social actions. Behavioral homologues of empathy have been observed in different non-human animals. For instance, it has been clearly established that rodents display emotional contagion of others’ distress, and are motivated to alleviate another rat’s distress. We found that rats intentionally released a cagemate trapped in a restrainer, even when social contact was prevented.  When a second restrainer containing a highly palatable food (chocolate chips) was present, rats opened both restrainers and typically shared the chocolate. Since only cagemates were tested, it is unclear if these behaviors generalize to strangers. Helping others is costly and resource depleting, and should thus be discriminately extended. In humans, the expression of empathically motivated pro-social behavior is dependent on social context, where people are more motivated to help in-group members than out-group members. Correspondingly, emotional contagion is modulated by familiarity in rodents. Mice have been found to display heightened pain sensitivity when witnessing a cagemate in pain, but not a stranger in pain. To investigate these questions, we are currently exploring the effect of social parameters such as familiarity and relatedness on the expression of empathic helping in rats.