The emergence of worker from mouse groups in a reward-threat conflict situation is related with their mPFC-BLA-NAc activity

Abstract

Despite the well-known notion that mice are social animals, whether or not a group of a mouse living together establishes a clear division of labor and if so, how the division temporally evolves, is largely unknown. Here we set up an ecological foraging experiment under which a mouse group is subjected to a reward-threat conflict situation. We used the CBRAIN (Collective Brain Research Aided by Illuminating Neural activities) telemetry system (Kim et al., Sci Adv, 2020) to track brain activities in the basolateral amygdala (BLA), nucleus accumbens (NAc), and medial prefrontal cortex (mPFC) of individual mice. Two types of individuals with distinct behavior repertoires were identified under behavioral analysis on more than 60 group foraging trials: workers and free-riders. Workers were the individuals that actively engaged in the foraging, while free-riders were the individuals who did not themselves bring the food, but took it from the workers. Moreover, behavioral patterns of mice became more solidified as foraging continued over days. Analysis of neural dynamics has found that the rate of oscillatory bursts in the beta (24 ？ 32 Hz) and gamma (40 ？ 70 Hz) frequency bands were significantly elevated in the workers compared to the free-riders. The information on individuals’ positions and brain activities at each time allowed us to compare the dynamics within the mPFC-BLA-NAc network of worker and free-rider mice. Our findings provide evidence of the dynamic establishment of the social division of labor within a mouse society, composed of individuals that vary in mPFC-BLA-NAc regulation depending on their social role.