HIPPOCAMPAL ENSEMBLE DYNAMICS DURING THE ACQUISITION OF PROSOCIAL RESCUE BEHAVIOR IN MICE

Prosocial behaviors, such as rescuing individuals in distress, are essential for promoting social cohesion and well-being across species. Although neural circuits supporting general social interactions have been increasingly characterized, the precise mechanisms governing complex prosocial actions remain incompletely understood. We previously established a rescue behavior paradigm in which mice learned to liberate a trapped conspecific and demonstrated that the dorsal hippocampus (dHPC) is essential for the acquisition of this behavior. Here, we used in vivo calcium imaging to investigate cellular dynamics within the dorsal CA1 (dCA1) as mice mastered the rescue task. Our findings reveal that rescue learning is associated with a progressive reorganization of the dCA1 network toward a more efficient state. As rescue performance improves, the network exhibits increased functional coactivity and global efficiency, characterized by the formation of synchronized neuronal ensembles. Crucially, we identified "liberation ensembles" selectively tuned to the moment of rescue. Learning drives a shift in these ensembles, with an enrichment of "pre-responsive" neurons active during decision-making and "post-responsive" neurons active during the social reunion. These findings demonstrate that even within classically cognitive regions such as the dHPC, specialized circuits are dynamically recruited to support complex prosocial behaviors. More broadly, they suggest that effective helping relies on the optimized functional organization of cognitive neural networks, providing a new framework for understanding interactions between cognition and prosocial actions. Finally, we discuss ongoing work examining how dHPC cognitive and prosocial circuits are reinforced across tasks with distinct social and non-social reward demands.