Critical periods revisited: implications for intervention with traumatized children.

t e e t d a u p a c s i b t r a b A w O ver the past decade there have been significant advances in the establishment of evidence-based treatments for traumatized children. Severely and multiply traumatized children, however, often have complex and difficult-to-treat clinical presentations. There is a perception among many clinicians, foster parents, and child protective service workers that these children are irrevocably “damaged”— especially when the trauma occurred during early developmental “critical periods.” The goal of this article is to review recent advances in neuroscience that debunk the myth that early severe adverse rearing experiences lead inevitably to bad outcomes and to discuss the clinical implications of this evolving work. The belief that early deviant experience can lead to permanent changes in brain development and behavior stems partly from the groundbreaking experiments on monocular deprivation in cats by Wiesel and Hubel. The development of central visual pathways in several mammalian species is known to be experience-dependent. Wiesel and Hubel deprived kittens of vision in one eye for different lengths of time and at different ages. They found that after suturing one lid during the first 3 months of life, there was no vision in that eye later in development after the sutures were removed, and the visual cortex did not develop normally. The effects of visual deprivation on subsequent brain development and visual processing was evident only in kittens, not in adult cats, which led to the conclusion that vision development in kittens has a “critical period,” and if the eyes are not exposed to the required stimuli during that period, vision would be lost and associated brain structures altered permanently. This finding has been extrapolated to traumatized children, generating the notion that q