The mechanisms of action of deep brain stimulation and ideas for the future development

Deep brain stimulation (DBS) has been used as a treatment of movement disorders such as Parkinson's disease, dystonia, and essential tremor for over twenty years, and is a promising treatment for depression and epilepsy. However, the exact mechanisms of action of DBS are still uncertain, although different theories have emerged. This review summarizes the current understanding in this field. Different modalities used to investigate DBS such as electrophysiological, imaging and biochemical studies have revealed different mechanisms of DBS. The mechanisms may also be different depending on the structure targeted, the disease condition or the animal model employed. DBS may inhibit the target neuronal networks but activate the efferent axons. It may suppress pathological rhythms or impose new rhythms associated with beneficial effects, and involves neuronal networks with widespread connections. Different neurotransmitter systems such as dopamine and GABA upregulation are involved in the effects of DBS. There are also technical advances to prolong the battery life and specific targeting based on new electrode designs with multiple contacts which have the ability to steer the current toward a specific direction. There is ongoing work in closed loop or adaptive DBS using neural oscillations to provide the feedback signals. These oscillations need to be better characterized in a wide variety of clinical settings in future studies. Individualization of DBS parameters based on neural oscillations may optimize the clinical benefits of DBS.