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230 EFFECTS OF STRESSprovide an excellent foundation for translational research that integrates basic andclinical approaches. Not only have behavioral effects consistently been observedin experimental attention paradigms relevant to anxiety, but the neural structuresinvolved in these effects have also been identified in multiple laboratories usinga variety of techniques, including relatively novel brain imaging approaches.Functional magnetic resonance imaging (fMRI) permits noninvasive assessmentof the neural correlates of various psychological processes, including attention tothreat cues. Because this technique is noninvasive and associated with minimalrisks, it can be used to examine developmental aspects of neural functioning aschildren pass through adolescence. fMRI provides an index of changes in bloodflow that occur while study participants perform cognitive tasks. This index reflectsdifferences in the magnetic susceptibility properties of oxygenated anddeoxygenated hemoglobin, arming the brain with its own “endogenous contrastagent,” such that increases in the flow of oxygenated blood are reflected in regionalpatterns of “activation” in fMRI scans.Although fMRI provides a novel means for developmentally oriented translationalstudies, such research remains difficult to conduct. One major problem isthat neuroscience studies of human fear typically employ highly aversive stimuli,including electric shocks, noxious smells, grotesque pictures, verbal prompts, andpharmacological compounds. Due to ethical restrictions, such stimuli cannot beused in research with children and adolescents. Other classes of stimuli, such asabstract verbal representations of fearful events, that are less noxious, also haveinherent limitations for use with youth. Because such stimuli often require sophisticatedelaborative processing, they may not evoke emotion as reliably in childrenand adolescents as they do in adults. One of the few stimulus classes that areboth ethically permissible for use with youth and adequately simple to processconsists of photographs of emotionally expressive facial displays. This class ofstimuli is well suited for developmental research on emotion and informationprocessing and thus has been employed in a wide range of studies in this area.Facial emotion displays show a striking capacity to induce emotion in primatesacross a variety of developmental stages, cultures, and species (Darwin, 1998; C. A.Nelson et al., 2002). The evocative quality of such displays have led to their widespreaduse as stimuli in studies of emotion processing in healthy children, adolescents,and adults (Haxby et al., 2002; Monk et al., 2003). Such studies havedemonstrated reliably that emotion and information processing interact in waysthat mediate both task performance and neural circuitry engagement. Taken together,these findings permit the generation of hypotheses regarding relationshipsbetween psychological processes and neural circuit function. For example, findingsindicate that angry faces, which signal interpersonal threat and thus constitutea salient stimulus for many anxious individuals, can engage attention andinterfere with performance on nonemotional tasks (Mogg & Bradley, 2002).Moreover, angry faces have been shown to be more memorable than other types