In addition to studying emotional processing at a conscious, cortical level, significant evidence suggests that many aspects of emotional processing occur below conscious awareness, at a preconscious level. The technique of backward masking assesses the automaticity of emotional processing and responses to affective stimuli. In MDD, backward masking serves to avoid confounding interpretation by the presence of other cognitive processing, which may result from depressed subjects perseverating on emotional stimuli. The proposed study builds on previous fMRI research to investigate neurophysiological differences in the processing of aversively conditioned emotional stimuli in depressed compared to healthy individuals. Using fMRI technology and a variation of the paradigm developed by Morris et al., subjects with MDD will be classically conditioned to the presence of an unmasked specific target face (angry or sad) and the subsequent neural responses to the stimuli will be assessed utilizing the backward masking technique. The BOLD hemodynamic response and rates of habituation and extinction to the faces will be compared between depressed subjects with MDD and healthy controls, currently depressed versus currently remitted subjects with MDD, and MDD subjects pre- and post-antidepressant therapy.