Virtual social interaction reveals that the dorsal habenula-IPN pathway is essential for targeting the opponent.

Conspecific social interaction is among the most important brain functions to be investigated. We designed a virtual reality (VR) system that enables real-time teleportation of head-fixed adult zebrafish movements onto their 3D avatars. To facilitate dyadic fight-like behavior in the VR space, we devised a task in which avoidance of periodic mild electric stimulation is achieved by attacking the opponent, and a transient electric shock acts as negative feedback for bite-like events. Moreover, a transgenic fish with an impaired dorsolateral habenula-to-interpeduncular nucleus pathway, known as a winner's circuit in social conflict, showed reduced ability in placing the opponent in the field of binocular view and attacking the opponent, while also showing increased use of the left eye. These indicate the importance of the winner's circuit in correctly aligning the body axis for capturing the opponent. The proposed VR system can be effective in investigating how the brain encodes various social interactions.