Assessment of Hedonic and Motivational States in Major Depression ( MOODDIS)

Major depression is a frequent psychiatric disorder with an estimated lifetime prevalence of 16-17% in the general population. Although its pathophysiology is not completely understood, a large body of literature pleads for a causative role of disturbances in reward processes, referring to: i) the hedonic sensation (i.e. "liking") defined by the pleasure felt after exposure to appetitive stimuli, and ii) the motivation (i.e. "wanting") represented by the ability to initiate and maintain behavioral responses oriented toward appetitive stimuli. the investigators have therefore developed and tested a new experimental computer-based and easy-to-use test intended to provide an objective and quantitative measurement of both hedonic and motivational states in humans. According to the task, the subjects are asked to view and to compare two stimuli, an appetitive one (food pictures) and its devalued counterpart (food pictures in greyscale), at each trial, assessing either the size (task A) or the duration of presentation (task B). From these considerations, the present project aims at using our novel tool to: i) assess the hedonic and motivational state in subjects with major depression, ii) compare their responses with healthy volunteers. The present project should demonstrate that the behavioral tests validated in our laboratory are relevant experimental tools for the diagnostic/clinical assessment and for the phenotypic characterization of depressed patients. The application of the test in the therapeutic context could add further information about the efficacy and relevance of the chosen therapy.