Orexin Drives Brain Waves for Empathy and Prosocial Actions in Mice

Empathy, often measured through observational fear in rodents, has been consistently linked to increased theta oscillations in the anterior cingulate cortex (ACC), a brain region critical for decision-making and emotion. However, the upstream circuit mechanisms that modulate these specific brain oscillations and the precise extent of their role in translating empathy into behavioral action have remained largely unknown. This study aimed to uncover these neural pathways.

The study found that ACC theta oscillations are indeed critically involved in empathy-driven prosocial allogrooming. They observed that orexinergic neurons were selectively activated in the ACC during both observational fear and prosocial allogrooming, but only when the mice had prior fear experience. This suggests a learned component to the empathetic response. The most significant finding was that optogenetic inhibition of lateral hypothalamic orexinergic inputs to the ACC not only suppressed theta power in the ACC but also reduced both observational fear and prosocial allogrooming behaviors by a statistically significant margin. This direct manipulation demonstrated that hypothalamic orexinergic inputs actively drive ACC theta oscillations, which in turn modulate these empathy-related behaviors, providing a clear causal link. The reduction in behavior was robust, indicating a strong dependency on this orexin-ACC pathway.