Electrical stimulation

This chapter explores electrical stimulation of excitable biological entities. It provides a brief history of electrical stimulation, stimulation parameters, theory of electrode interface impedance, and types of stimulation. Focus is on the technology of charge balancing, power losses, voltage compliance, and associated hardware complexities of electrical stimulators. Stimulus artifacts and inductive power delivery are also discussed, and are often used with stimulators for applications in neural prostheses and therapeutics [1, 2]. Introduction Electrical stimulation is an important and popular method in which injected charges are mainly responsible for excitation or inhibition of neural or motor structures [3-5]. It can be utilized for treatment of diseases and restoration of dysfunctional organs, such as for the brain [6, 7], retina [8, 9], cochlea [10], or peripheral nerve [11]. The electrical stimulation process is accomplished by using conductive electrodes of specific size and shape, which are placed at desired biological sites of interest. Coulombic charge is injected through such electrodes by means of constant current or constant voltage pulses. Charge injection accuracy, power loss minimization, output voltage compliance, and miniaturization are important factors that can enhance practical performance in electronic stimulators [12]. In the following subsections we provide a brief history and introduce technical parameters associated with electrical stimulation.