NEUROBIOLOGICAL BASES OF BEHAVIORAL-DEVELOPMENT IN THE FIRST YEAR

This review summarizes the temporal relations between selected psychol ogical milestones in the first year of the human infant and theoretica lly relevant developmental neurobiological changes in the brain, suppl emented where appropriate, with evidence from the non-human primate, T he disappearance of the palmar grasp reflex and the decrease in endoge nous smiling and spontaneous crying, which occur at 2-3 months, are co rrelated to emergent cortical inhibition of brainstem circuits, In add ition, the improved ability to recognize an event experienced in the i mmediate past (recognition memory) is related to growth of the hippoca mpus and adjacent structures at this age, The behavioral developments at 7-10 months include an enhanced ability to retrieve stored represen tations of the past and to compare past and present (working memory), along with the emergence of the universal fears of strangers and separ ation from the caretaker. These milestones are correlated in time with maturational changes in the prefrontal and rhinal cortices and hippoc ampal formation, the integration of the limbic system and increased re sponsiveness of the hypothalamus-pituitary-adrenal axis. Knowledge of age-dependent correlations of brain and behavioral maturation is a bas is for the investigation of causal relationships between brain develop ment and behavior. A close collaboration of pediatricians, psychologis ts and neuroscientists is, therefore, necessary.