Deep brain stimulation involves the placement of electrodes in the brain to treat specific movement disorders such as: parkinson's disease, essential tremor and dystonia. These electrodes are connected to an implanted pulse generator, similar to a pacemaker for the heart. The pulse generator stimulates a deep location in the brain, modulating its function and altering the patient's symptoms. In parkinson's disease the target of stimulation is frequently the subthalamic nucleus (STN) or the globus pallidus interna (GPi). In patients with essential tremor the focus of stimulation is the ventralis intermedius nucleus (VIN) of the thalamus. Stimulation of these targets has been shown to improve motor performance. Stimuation of the STN in patients with parkinsons disease allows for a reduction in their antiparkinson medications.