The brain of the developing organism is a unique and dynamic system. During the prenatal and postnatal periods the brain differs dramatically from that of the adult. For example, it contains more synapses early in development than it does at any other stage in life (Purves and Lichtman, 1980). Receptors for a number of neuropeptides (e.g., oxytocin) are found in higher concentrations early in development than later in life (Shapiro and Insel, 1989). In certain brain areas (e.g., the suprachiasmatic nucleus of the hypothalamus), glucocorticoid receptors are found in high concentrations only during early ontogeny (Van Eekelen et al., 1987). These are but a few examples that attest to the differences in the brain during development. For the most part, scientists have not determined the functional significance of these neuronal features of the newborn brain.

One of the critical aspects of the developing...