Psychobiological stress regulation and aggression: Investigations on the dimensionality of externalization

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The externalizing spectrum is characterized by disinhibition/impulsivity, antisocial-aggressive behavior as well as substance use and misuse. The major aim of the proposed project is to investigate the thesis that interindividual differences in externalizing behavior are associated with neuronal, emotional, cognitive and psychoendocrine stress regulation. We also postulate that differences in the extent of externalizing behavior predict aggressive behavior rates after acute stress exposure and that externalizing behavior is related to differential neuronal activation patterns during aggression induction. Although externalizing is characterized by altered emotional reactivity, to date, there is a lack of data on psychological and psychobiological stress regulation. Externalizing is not a categorical but a continuous construct. Thus, externalizing behavior will be investigated across a wide range of normal variation in a homogenous and well-characterized sample of normal and healthy adults. This approach allows to minimize otherwise typical confounding factors like comorbidity (e.g., in psychiatric and forensic samples) or significant contextual conditions (e.g., incarceration). To evaluate if our findings in subjects from the general population can be generalized to clinical samples, we additionally examine a forensic sample of men characterized by an early-acquired and persistent pattern of antisocial-aggressive behavior. As biological outcome measures, we propose assessing endocrine parameters (cortisol, testosterone); as psychological variables, we plan measuring emotional and cognitive responses to acute stress exposition. We expect dissociations between endocrine stress responses on the one hand and emotional and cognitive stress responses on the other. Applying an experimental design (acute stress induction versus control condition) we also investigate behavioral effects in a standardized acute aggression-induction-paradigm. We expect a higher rate of aggressive behavior after aggression-induction in subjects with a higher degree of externalization (in particular in subjects with forensic background) as well as associations between indices of aggressive behavior and emotional and endocrine responses to stress. A further important aim of the present project is the investigation of neuronal activation patterns during acute stress as well as aggression induction during functional magnetic resonance imaging (fMRI). We expect that the individual degree of externalization is associated with specific neuronal response patterns in, for example, the amygdala, cingulate cortex and prefrontal cortex.