Initially Deep Brain Stimulation was thought to act like the functional ablation, after many studies showed DBS acts by antidromic activation and that responses depend on both GABAergic and glutamatergic transmission. This understanding helps greatly on weighing the risk-benefits ratio of treatment, because the advances of psychosurgery technological benefits have dramatically increased while the risks have been reduced. In the course of time, we come to realize that different parts of the brain do different things. There are areas of the brain dedicate to control your movement, vision, memory and so on. When these work well, the nervous system works well and everything is function. However, once in the while, things do not go so well and there is trouble in the circuits, where some neurons misfire and causing trouble, or sometime they are underactive and they are not working, as they should. The manifestation of this depends on where in the brain these neurons are. So when these neurons in the motor circuit, motor dysfunction will result, such as Parkinson disease. When the malfunction in the circuit that regulate your mood you will get depression or mania, and when it is in the memory you will get Alzheimer disease. The main principle of DBS is to interfere with the circuit and turn them up or turn them down. What makes DBS superior to ablation? DBS can be adjusted based on the symptoms or the progress of disease and overall it is reversible, and less damaging than lesion surgeries.