In the present study, investigator will investigate the effects of methylphenidate (40 mg) on mPFC activity in healthy male volunteers during fear extinction using functional magnetic resonance imaging (fMRI). Additionally, investigators will examine the effects of methylphenidate during aversive interoceptve arousal. The present study will help to identify brain structures and networks involved in anxiety and will give insights for methylphenidate as a possible adjunct to behavioral therapy for patients with anxiety disorders. Further, this study may provide important information about the possible use of fMRI to help the development of drugs for the treatment of anxiety disorders.