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Chapter 6Stress Effects on the Developing BrainMegan R. GunnarAlthough stress is often construed as something bad (e.g., Sapolsky, 1996), wehave known for a long time that it’s not exposure to stressors that has ill effects,but how we react to stressors that can contribute to physical and mental problems(Lazarus & Folkman, 1984; Selye, 1977). How we respond is intimately relatedto the neurophysiology of stress and emotions, and to the role that the stressemotionsystem has played in survival throughout our evolution (LeDoux &Phelps, 2000; Porges, 1995a). At its core, the stress-emotion system is a defensemotivational system. In response to situations that pose potential threats to ourwell-being, it allows us to mobilize defensive responses, shunt physical resourcesto the mobilized target organs, shift from storing to using energy, alter prioritiesfrom preparing for the future to responding to immediate circumstances, narrowand heighten perception to threat-relevant cues, and increase the salience of threatrelevantmemories.Over the last half century, researchers have come to understand a great dealabout the stress-emotion system, its impact on mental and emotional health, andthe weaving of genes and experiences that shape the organization of the stressemotionsystem during development (for review, see Gunnar & Vazquez, 2006).Much of this work has been based on animal models (c.f., Sanchez, Ladd, &Plotsky, 2001); however, with the new tools of neuroscience, the emergenceof the field of affective neuroscience, and the modification of assays to allow127