We will use isolated, low doses of DCS in the proposed project. When used to treat psychiatric symptoms or cognitive impairments in children the typical dose is 50-100mg. A meta-analysis of the effect of DCS augmentation of fear extinction and exposure therapy did not find significant dose related effects across studies but in the one clinical study that systematically investigated doses, there was some evidence of greater efficacy with a higher dose. In the proposed study participants will receive 100 mg of DCS. The same meta-analysis found that the best effects were evident when DCS was administered either immediately before or after exposure training compared to a four hour delay. Animal models and human studies suggest that DCS does not affect performance during training; instead, it selectively improves memory consolidation for new learning typically assessed 24 hour after training. The acute physiological effects of DCS on brain activation, however, can be observed two hours after DCS administration on fMRI.