Complex social dominance behavior using a novel platform test is associated with lateral habenula activation in male and female mice

Social hierarchy influences behavior, resource access, and health, but the neural mechanisms underlying individual differences in social competition remain incompletely understood. Using a novel competitive platform test and assessment of region-specific activation in male and female mice, we found a range of social hierarchies as determined by time on platform, revealing greater behavioral complexity than previously described and improved stability in females. We also measured motivated behavior and saw reduced platform acquisition attempts over testing days as well as rank-dependent differences in platform co-occupancy, which were seen primarily amongst lower ranks. We found no association between rank and medial prefrontal cortex (mPFC) activation, but found a positive correlation between lateral habenula (LHb) activation and rank. Social dominance was magnified in a group setting compared to paired matchups with similar motivation and co-occupancy behavior between ranks. There was no association between rank and mPFC activation in a group setting, but the LHb was again positively correlated with rank. Collectively, these findings demonstrate that the competitive platform task captures individual differences in social competition, motivation, and resource-sharing behavior under an aversive stimulus and identify the LHb as a neural correlate of performance in this behavioral context. These results highlight the complexity of social interactions in both sexes and provide insight into neural mechanisms that contribute to competitive social behavior.