s / Brain Stimulation 7 (2014) e1ee16 e5 excitatory tDCS over the primary motor cortex and inhibitory tDCS over the dorsolateral prefrontal cortex on procedural memory acquisition and consolidation. Methods: Forty active duty military volunteers were randomly assigned to one of four groups (10 per group); anodal (excitatory) tDCS over motor cortex (M1), cathodal (inhibitory) tDCS over dorsolateral prefrontal cortex (DLPFC), both anodal tDCS over M1 and cathodal tDCS over DLPFC, or sham tDCS. Participants learned a set of procedures for identifying aircraft as friend or foe over four 5minute trials while receiving their tDCS condition. Twenty-four hours later, participants returned for retention testing consisting of 4 more trials. Results: The results showed significant main effects of stimulation type and trial on task performance during the training session and retention test (p<0.05). The three stimulation groups showed significantly better task performance when compared to the sham group in retention (p<0.05). The cathodal tDCS only group showed significantly better performance as compared to all groups in the retention test. Discussion: The results suggest that inhibition of the prefrontal cortex using cathodal tDCS leads to the greatest improvement in both procedural memory acquisition and retention. It is hypothesized that this is a result of a shift in dominance of the declarative memory system to the non-declarative procedural system, which improves acquisition and consolidation of the proceduralmemories gained during training. ** Volunteer Research Affiliate 11 The outcomes and acceptability of tDCS in opioid-treated patients with unrelieved chronic pain Ricardo A. Cruciani , Ethan P. Davoudzadeh *, Aaron Greenberg , Helena Knotkova a,b a Institute for Non-Invasive Brain Stimulation, Department of Pain Medicine and Palliative Care, Beth Israel Medical Center, New York, NY, USA Department of Neurology, Albert Einstein College of Medicine, Bronx, NY, USA Department of Anesthesiology, Albert Einstein College of Medicine,