PUPILLOMETRY AND BRAIN-WIDE C-FOS MAPPING REVEAL MULTIMODAL MIRROR NETWORKS UNDERLYING EMOTIONAL CONTAGION IN MICE

Emotional contagion (ECo) is a basic form of empathy in which the emotional state of one individual is shared by another. In this study, we quantified ECo in mice using pupillometry while an observer animal witnessed a conspecific receiving tail shocks. Analysis of pupil dynamics allowed the estimation of both direct and vicarious emotional response thresholds at the individual level through psychometric modeling. Observer pupil dilation was reduced when visual access to the demonstrator was prevented, indicating the involvement of visual cues, and was also elicited by viewing videos of shocked conspecifics. To investigate the neural substrates of ECo, we performed brain-wide c-Fos mapping using light-sheet fluorescence microscopy. This approach identified a distributed network of 88 brain regions engaged during ECo, with overlapping activation patterns in demonstrator and observer animals. Moreover, several regions showed correlated activity between paired observer-demonstrator subjects, suggesting the emergence of shared neural states during emotional transfer. Together, these findings provide insight into the brain-wide organization of emotional contagion and support the use of pupillary responses as a quantitative readout of shared emotional processing, with potential relevance for translational studies and models of neuropsychiatric disorders.