Early experience and the development of stress reactivity and regulation in children

Abstract

Children who spend early portions of their lives in institutions or those maltreated in their families of origin are at risk for developing emotional and behavioral problems reflecting disorders of emotion and attention regulation. Animal models may help explicate the mechanisms producing these effects. Despite the value of the animal models, many questions remain in using the animal data to guide studies of human development. In 1999, the National Institute of Mental Health in the United States funded a research network to address unresolved issues and enhance translation of basic animal early experience research to application in child research. Professor Seymour Levine was both the inspiration for and an active member of this research network until his death in October of 2007. This review pays tribute to his legacy by outlining the conceptual model which is now guiding our research studies.

Figure 1

This represents the Center’s working model. It is purposely general enough to apply to the various model systems (rodent, non-human primate, human) studied by Center faculty. The model assumes that both genes and environment will influence developing vulnerability to emotional and behavioral disorders. The partially converging arrows running from left to right are meant to suggest diminishing (but continuing) plasticity of the neurobiological systems underlying risks for emotional and behavioral disorders. The facets of neurobiology depicted in the model are the neurobiology of stress and the neurobiology of rapid threat appraisal and response, along with developing behavioral and emotional regulatory systems. Stress- and Threat-response systems are depicted to the left within a larger circle to indicate their earlier emergence in development. The circular arrows connecting these two systems are meant to reflect their mutual influence on one another. Emotional and behavioral regulatory systems reflect cortico-limbic systems whose development is depicted to the right to indicate that it is somewhat later developing. The circular arrows drawn between emotional and behavioral regulatory systems and the circle containing the stress- and threat-response systems indicate mutual influence across development. Finally, the aspect of the environment most notable to our Center’s model is shown along the bottom of the figure. This is the caregiving regulatory system. The spacing of the arrows is designed to indicate that this system has more influence earlier in development, but depending on the species, may continue to play a role well for prolonged periods of the organism’s life.

Figure 2

Relation between low and high maternal responsivity and reactivity of stress and emotion sensitive systems. Panel A. Cortisol responses to inoculations at 18 months in children whose mothers were low or normal to high responsive during the first 6 months of the infants lives. Adapted from Gunnar et al. (1996). Panel B. EEG asymmetry in infants of low versus high responsive mothers. Note that negative EEG asymmetry scores indicate right-biased activity associated with increased withdrawal affects, including depression. Adapted from Hane and Fox (2006).