 In order to assess the role of dopamine in anhedonia and in reward processing, we propose to assess the effect of dietary tyrosine plus phenylalanine depletion on the neural and behavioral responses associated with the performing of the monetary reward tasks investigated herein in an additional sample of subjects. Dietary depletion of tyrosine and phenylalanine, two DA precursors, is a validated method to induce significant reduction of the brain DA concentration as shown in two previous 11CRaclopride PET studies. We hypothesize that depressed patients will show less activation than controls in brain regions associated with the mesolimbic DA system, such as striatum, amygdala, anterior cingulate gyrus and orbitofrontal cortex in response to reward in the placebo condition. We expect tyrosine and phenylalanine depletion to induce a similar neural impairment to reward in healthy subjects, including a reduction of the neural activation in the striatum, amygdala, anterior cingulate gyrus and orbitofrontal cortex in response to reward. The reduction of the neural activation in those regions will be stronger in healthy controls than in depressed patients. Finally, we hypothesize that tyrosine depletion will influence negatively the valence ratings of rewarding stimuli in healthy subjects. In depressed patients, anhedonia scores will correlate negatively with the valence ratings of rewarding stimuli in the placebo condition already. 