Investigation of empathy in terms of age and memory

Abstract

Empathy enables us to share and understand the feelings of others, and it is a necessary ability for social animal such as human. Empathy had been considered as a unique trait of mankind; hence most of research had focused on human-beings. In recent years, empathy has been studied in rodents to unveil the neural mecha-nism in many quarters. However, neural basis of empathy has not been investigated enough from the standpoint of acquired characteristic, such as social memory acquisition and development. To study the acquired characteristic of empathy, two hypotheses were established and behavioral experiments with mice were performed. First, memory formation through social interaction will be necessary for the expression of empathy. Thus CaMKIIα+/- mice which have a deficit in memory retention are expected to be unable to show empathy. Sec-ond, if accumulation of social experiences is needed for empathy maturation, empathic response will not be elicited enough in the early age. Hence, higher level of empathy is expected to be observed in adult mice than in juvenile mice. Observational fear learning was employed as a behavioral assay to assess the level of empathy.In the result of experiments, CaMKIIα+/- mice showed impairment in observational fear learning. Deficit of CaMKIIα+/- mice in observational fear learning was confirmed to be independent of fear response and hyper-activity. In addition, increased level of response was observed in adult mice compared to juvenile mice. Low level of empathic response in juvenile mice was unrelated to the immaturity of fear response in early age.In conclusion, both memory deficit and lack of social experience resulted in decreased level of empathy. These behavioral results of mice are the first studies about the acquired characteristics of empathy in terms of age and memory so far. The results imply that not only innate genetic component but also memory acquired by social interaction with surrounding environments through de...