Deep brain stimulation (DBS) is a widely used therapy for movement disorders such as Parkinson's disease, essential tremor, and dystonia. Its therapeutic success has led to the application of DBS for an increasing spectrum of conditions. However, the fundamental relationships between neural activation, neurochemical transmission, and clinical outcomes during DBS are not well understood. Drawing on the clinical and research expertise of the Mayo Clinic Neural Engineering Laboratories, this book addresses the history of therapeutic electrical stimulation of the brain, its current application and outcomes, and theories about its underlying mechanisms. It reviews research on measures of local stimulation-evoked neurochemical release, imaging research on stimulation-induced neural circuitry activation, and the state of the art on closed-loop feedback devices for stimulation delivery.