Postnatal maturation of the basolateral and paralaminar amygdala in rodents: implications for social–emotional development

Across vertebrate species, the amygdala is a central node of the social brain network, an interconnected set of nuclei for regulation of innate and learned social and emotional behaviors. The amygdala undergoes significant structural and functional changes from juvenile to adult stages of life, driving the emergence of complex social and emotional behaviors. Focusing primarily on rodent animal models, in this review we describe the dramatic changes that unfold from juvenile stages to young adulthood in two amygdala nuclei that undergo significant post-natal growth, the basolateral amygdala (BLA) and paralaminar nucleus (PL). Interestingly, while both the BLA and PL mature during post-natal stages, neurons in the BLA mature earlier than the PL. The differing maturational rates along with differences in input/output connectivity of these nuclei indicate that they play complementary roles in the emergence of amygdala-driven social-emotional behaviors, such as responses to fear, social hierarchical behaviors and responses to novel cues. The post-natal development of the BLA, and likely the PL, which is less well studied, is highly shaped by the environment, particularly the quality of early caregiving. Understanding the developmental processes that unfold during this critical period of life and their sensitivity to environmental disruption will be key to developing biologically informed interventional strategies for a host of human disorders characterized by neuro-atypical social-emotional behaviors.