Early development of the social and emotional brain in infancy

Abstract

An important function of the brain is to scan one’s surroundings for the presence of biologically relevant features and grant them priority for attention and action. The significance of this function for an individual’s well-being and survival has given rise to the argument that specialized neural mechanisms for processing biologically salient stimuli may exist and that these mechanisms may require little, if any, experience for normal development. As evidenced by behavioral studies, the ontogeny of this network and associated cognitive capacities may emerge before the age of one year. With technological advances in recent years, researchers have been able to utilize electroencephalography, functional near-infrared spectroscopy, and functional magnetic resonance imaging to directly explore the early development of social-emotional brain mechanisms. In this paper, we systematically review three major aspects of early social and emotional development in infancy—facial expression, emotional voice, and early socialization. Based on empirical evidence, we describe the developmental process of the corresponding social and emotional neural network. We then discuss the impact of early social experience on the development of the social and emotional brain in terms of experience-expectant and experience-dependent mechanisms. We argue that the social-emotional neural network is not a congenital processing module that is independent of social experience. The core structure of the human social and emotional brain seems to reach anatomical maturity relatively early in development (zero to three months); however, the basic organization of the social-emotional network may be specified by an experience-expectant neural circuitry that emerges at five to seven months of age and is rapidly refined by exposure to universal features of social experience during a sensitive period of development. The network retains some plasticity throughout a person’s lifetime and can be fine-tuned by individual-specific experiences, i.e., experience-dependent development. Functional connectivity between emotion-processing networks and other prefrontal regulatory systems continues to develop into adolescence. Finally, based on the present study of the early development of the social and emotional brain, we indicate three promising directions for future research.