Effects of Modafinil, Caffeine and Methylphenidate in Healthy Volunteers

Inclusion Criteria: * Men * 18 - 35 years * Written consent (according to Arzneimittelgesetz (AMG) § 40 (1) 3b) * Good knowledge of German * Right-handedness Exclusion Criteria: * Known hypersensitivity to the study medication * All contraindications to the study medication: arrhythmia, hyperthyroidism , glaucoma , pheochromocytoma , congestive heart failure , diabetes mellitus, known liver and kidney dysfunction, vascular disease , angina, haemodynamically significant congenital heart disease , cardiomyopathy , myocardial infarction, channelopathies, arterial hypertension , cerebrovascular diseases , such as cerebral aneurysm , vascular abnormalities , including vasculitis and stroke. * Participation in other clinical trials during or within one month prior to this clinical trial * Medical or psychological circumstances that may endanger the proper conduct of the trial * Existing serious somatic diseases, even if they are not covered by the contraindications according to product information * Existing psychiatric disorders and psychiatric disorders in prehistory * Smoker or ex-smoker for less than 5 years * Regular caffeine consumption \> 4 cups per day * Subjects with irregular day -night rhythm (eg shift workers ) * Unwillingness to the storage and disclosure of pseudonymous data as part of the clinical trial * Accommodation in an institution by court or administrative order (according to AMG § 40 (1) 4 ) * MRI contraindications ( eg pacemakers , metallic or electronic implants , metallic splinters , tinnitus, surgical clips )