Although electrophysiologic dysfunction of the subthalamic nucleus is putative, deep brain stimulation of this structure has recently been reported to improve obsessions and compulsions. In Parkinson disease, sensorimotor subthalamic neurons display high-frequency burst firing, which is considered as an electrophysiologic signature of motor loop dysfunction. We addressed whether such neuronal dysfunction of the subthalamic nucleus also exists in the nonmotor loops involved in patients with obsessive-compulsive disorder.