Awareness to injurious behavior in animals

Abstract

Injurious behavior to others can be induced by empathy deficit in humans, which has been considered one of the causes of the social problem such as a random murder. However, there is no proper behavioral paradigm and animal models for studying a mechanism of injurious behavior to others, so it has been hard to investigate in rodents. Here, to examine the behavior in mice, we suggested an experimental design that if one mouse (observer) poked his nose into a hole, then the other mouse (demonstrator) in an opposite side got an electric shock. The number of nose-poking by observers was much lower in a shock condition than that in no shock conditions or random shock condition. Pharmacological inactivation of the anterior cingulate cortex (ACC) or the medial prefrontal cortex (mPFC), which is related to empathic behavior, increased the level of nose-poking in normal mice. Additionally, we developed a chronic social stress model which sequentially went through maternal isolation, social defeat, and long-term social isolation. When mice were got a maternal separation or a social isolation stress alone, they did not show any significant difference in the number of nose-pokings compared to that of control group. Thus, complex stress model is needed and the chronic social stress model is going to be a subject of injurious behavior test. Together, this study could be useful to investigate empathy deficit induced injurious behavior mechanism in mice and might help to understand psychiatric disorders related to injurious behavior to others in humans.