The hippocampus is particularly laden with n-methyl-d-aspartate (NMDA) receptors, and is at the same time one of the most important sites in declarative memory. The rationale of this study is that the NMDA partial agonist D-Cycloserine will promote learning compared to a placebo. On the other hand, the NMDA receptor antagonist Memantine might lead to reduced memory. We believe that the influence of NMDA receptors on memory can be determined via acute co-activation of the NMDA receptors with Cycloserine® (King Pharmaceuticals Ltd, active ingredient: DCycloserin, dose: 250 mg) and Memantine (Axura®, Merz, active ingredient: Memantine, dose: 20 mg)on both a behavioral and functional (fMRI) level.