Interference-free, lightweight wireless neural probe system for investigating brain activity during natural competition.

Competition is one of the most fundamental, yet complex, conflicts between social animals, and previous studies have indicated that the medial prefrontal cortex (mPFC) region of a brain is involved in social interactions. However, because we do not have a lightweight, wireless recording system that is free of interference, it is still unclear how the neural activity of the mPFC region is involved in the diverse, interacting behaviors that comprise competition. Herein, we present an interference-free, lightweight, wireless neural probe system that we applied to two mice to measure mPFC neural activities during a food competition test. In the test, we categorized 18 behavioral repertoires expressed by the mice. From the analysis of the neural signals during each repetition of the test, we found that the mPFC neural activity had the most positive correlation with goal-driven competitive behaviors, such as guarding resources and behaviors related to the extortion of resources. Remarkably, we found that the neural activity associated with guarding behavior was higher than that of extorting behavior, and this highlighted the importance of resource-guarding behavior for winning the competition, i.e., 'winning a trophy is hard, but keeping it is harder'. Our approach in which a wireless system is used will enable in-depth studies of the brains of mice in their natural social interactions.