We propose to study approach/avoidance behavior as measured by the Approach Avoidance task in 20 epilepsy patients undergoing implementation of depth electrodes for seizure monitoring in the Epilepsy Monitoring Unit at MGH. We will also study the effects of VC/VS electrical stimulation on approach-avoidance conflict in 20 adult patients who have undergone DBS implantation for severe MDD and/or OCD. There are 100-200 patients in the world with DBS electrodes in the VC/VS, and our research team cares for more than any other institution. Both participant groups will be assessed with respect to reward-aversion decision conflict using the task. The task will be performed with concurrent EEG recordings in DBS patients, and with continuous recording through our invasive neurophysiology rig in EMU subjects.