[Neurobiology of pair-bonded sociality in prairie voles]

Our understanding of the neural mechanisms underlying social behavior has been advanced by research using mice and rats. Specifically, the dorsal hippocampal CA2 area, ventral hippocampal CA1 area, and nucleus accumbens have been identified as critical for social recognition, while the medial preoptic area serves as a central hub for parental behavior. However, these polygamous species are unsuitable for studying "pair bonding"-an enduring, selective preference for a specific mate. To address this, this review focuses on monogamous prairie voles. Pair bond formation requires neuromodulators-including vasopressin, oxytocin, and dopamine-acting synergistically within reward regions such as the nucleus accumbens and ventral pallidum to associate partner-specific sensory cues with reward value. Recent studies further reveal that specific neural dynamics in the medial prefrontal cortex and nucleus accumbens dynamically regulate bond formation, and that the ventral hippocampal CA1 neurons exhibit partner-specific activity. Comprehensively, understanding the biological principles of sociality requires integrating the social identification mechanisms elucidated in mice with the valuation mechanisms demonstrated in prairie voles. Elucidating how the brain distinguishes the specific individual from the others and encodes him/her as "special" remains a key challenge for the future of social neurobiology.