This study aims to determine the effects of the anesthetic drugs thiopental, propofol, midazolam, and dexmedetomidine on the acquisition and early extinction on Pavlovian fear conditioning, and on the unconscious processing of fearful stimuli. If these anesthetic drugs can be shown to affect memory processes in the hippocampus and amygdala, there is a strong theoretical basis for their use in amygdala-based pathologies, such as augmentation of PTSD deconditioning therapies. This study received funding from the National Institutes of Health (Bethesda, MD, USA; K08 GM083213).