 In this study, which is part of the European research project MATRICS Multidisciplinary Approaches to Translational Research, the investigators focus on testing an innovative, non-pharmacological therapeutic approach for adolescents with a specific, difficult to treat subtype of aggressive behavior problems. Participants will be trained to acquire control over their own physiological parameters, in case of this study the activation of certain brain areas. While trying to control these parameters, participants get direct continuous feedback about their physiological state and its changes, and are rewarded for successful manipulation. Biofeedback methods are currently used to treat patients with a variety of psychiatric disorders such as attention-deficithyperactivity disorder ADHD. 