LAUSR

Emotional contagion is the most ancestral form of empathy. We tested to what extent the proximate mechanisms of emotional contagion are evolutionarily conserved by assessing the role of oxytocin, known to regulate empathic behaviors in mammals, in social fear contagion in zebrafish. Using oxytocin and oxytocin receptor mutants, we show that oxytocin is both necessary and sufficient for observer zebrafish to imitate the distressed behavior of conspecific demonstrators. The brain regions associated with emotional contagion in zebrafish are homologous to those involved in the same process in rodents (e.g., striatum, lateral septum), receiving direct projections from oxytocinergic neurons located in the pre-optic area. Together, our results support an evolutionary conserved role for oxytocin as a key regulator of basic empathic behaviors across vertebrates. Description Fundamentals of empathy Emotional contagion, in which individuals display fear or distress behaviors in response to observations of the same in another, is considered a basal form of empathy and is known to occur in fishes. Akinrinade et al. have shown that the neuropeptide oxytocin is responsible for these behaviors in zebrafish, as it is in mammals (see the Perspective by DeAngelis and Hofmann). They also found that the same regions of the brain are involved in zebrafish and in mammals. Such homologies in emotional response mechanisms across fishes and mammals suggest that this most basal form of empathy could have evolved many, many millions of years ago. —SNV Oxytocin plays an evolutionarily conserved role for as a regulator of basic empathic behaviors across vertebrates.