EN
INTRODUCTION: Social complex behavior, like empathy, emerge over phylogeny from various precursors. One of the simplest is emotional contagion, i.e. sharing emotional states between individuals. Receiving signals of a potential danger may increase chances of survival, thus emotional contagion plays an important role in learning about external environment. The phenomenon is well described at the behavioral level, but the neural circuits necessary for sharing emotions are unknown. We designed a rat model of fear contagion and showed that a brief social interaction with a fearful cage mate promotes risk assessment behavior and activates the central amygdala (CeA) in an otherwise naïve rat. AIM(S): The purpose of this project was to elucidate the role of the CeA circuits involved in socially shared fear. METHOD(S): To investigate the functional outputs of the activated CeA neurons, we mapped neural circuits downstream from the CeA combining anterograde tracing with an imaging of activated neurons in transgenic “Venus” rats. To test the function of CeA “social fear” neurons, we optogenetically stimulated or inhibited subpopulation of CeA neurons activated by social interaction using c-fos-driven targeting of channelrhodopsin and halorhodopsin. RESULTS: In rats that socially shared fear of their partners, we observed strong activation of structures involved in anxiety and motor functions. Most of the activated cells received projections from the CeA. Optogenetic activation of the “social fear” neurons in a social context led to behavioral pattern resembling the one observed during social interaction with a fearful partner. Activation of neurons in non-social context induced exploration and risk assessment behavior (active fear). Inhibition of them had the opposite effects. CONCLUSIONS: The results suggest that the CeA neurons involved in socially transferred fear mediate active fear responses and anxiety-related behaviors in both social and non-social conditions.