ABSTRACT
An outstanding feature of the neonatal mammalian brain is its plasticity, the process whereby its functional capacities, which are loosely specified by genetic makeup, are sharpened and crystallized through interaction with the external environment. Characteristic of this developmental plasticity are “critical periods” during which specific interactions between the growing brain and its environment are required for normal development. Examples of critical periods are found in systems as diverse as imprinting, birdsong, sexual differentiation, social behavior, sound localization, binocular vision, and somatosensory maps. While this developmental plasticity provides the organism with adaptability to the external world, it also produces the risk of developmental abnormality when the brain/environment interaction is less than optimal.
