Behavioral and genetic study on postnatal factors of empathy: the differential contributions of social context and brain areas on observational fear learning

Abstract

To investigate postnatal traits of affective empathy, observational fear learning (OFL) for mice was mainly used, and two approaches, behavioral and genetic study, were considered in an integrated manner. The first is a perspective of the behavioral study. I investigated putative influential factors on the empathic fear response based on the intrinsic-extrinsic framework. Not intrinsic factors, but extrinsic factors were found to be critical in OFL. Hierarchical interrelationship, rather than any potential changes in intrinsic traits due to the experience of dominant/subordinate hierarchy, was found to be influential on OFL. The second is a perspective of the genetic study. Calcium/calmodulin-dependent protein kinase II alpha (CaMKIIα) was conditionally deleted in a temporal/region-specific manner to see the causal effect on empathy. Dorsal telencephalic deletion of CaMKIIα and temporal specific CaMKIIα deletion after adult age was enough to induce impairment in OFL. CaMKIIα deletion in the medial amygdala (MeA) impaired OFL with unfamiliar partners, while deletion in the anterior cingulate cortex (ACC) impaired OFL only in the case of familiar partners. In summary, not intrinsic attributes, but extrinsic factors were found to be influential in affective empathy. And the differential contributions of brain areas on empathy were elucidated by conditional deletion of CaMKIIα. These exertions are expected to contribute to scientific comprehension of postnatal characteristics and neural correlates of affective empathy.