Neurological bases of behavioral development in infancy.

This article presents selected psychological competences that emerge in children during the first 2 years, together with correlated structural, biochemical and physiological changes in the brain. Major behavioral events of the 1st year are the disappearance of the neonatal reflexes, the improvement of recognition and working memory and the appearance of the universal fears of strangers and of separation from the caretaker. These behaviors are correlated in time with changes in the brain that allow the increased ability of the cortex to inhibit brainstem reflexes, with processes in the prefrontal cortex and hippocampus that facilitate the formation, storage and retrieval of memories, and with strengthened connections between the cortex and limbic system. Behavioral events of the 2nd year include the explosion of language and the emergence of self-awareness, both of which depend on the capacity for inference. The emergence of these capabilities is correlated with the intensified connectivity of the two hemispheres, the maturation of the prefrontal cortex and cortical-subcortical network.