Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. The subthalamic nucleus is a small lens-shaped nucleus in the brain where it is a part of the basal ganglia system. As suggested by its name, the subthalamic nucleus is located ventral to the thalamus. It is also dorsal to the substantia nigra and medial to the internal capsule. It was first described by Jules Bernard Luys in 1865, and the term corpus Luysi or Luys'' body is still sometimes used.