Journal of Neuroscience Methods 141 (2005) 171–198

Invited review

Electrical stimulation of excitable tissue: design of efficacious and safe protocols
Daniel R. Merrilla,∗ , Marom Biksonb , John G.R. Jefferysc
Department of Bioengineering, University of Utah, 20 South 2030 East, Biomedical Polymers Research Building, Room 108G, Salt Lake City, UT 84112-9458, USA b Department of Biomedical Engineering, City College of New York, New York, NY, USA Division of Neuroscience (Neurophysiology), School of Medicine, The University of Birmingham, Birmingham B15 2TT, UK Accepted 12 October 2004 a c

Abstract The physical basis for electrical stimulation of excitable tissue, as used by electrophysiological researchers and clinicians in functional electrical stimulation, is presented with emphasis on the fundamental mechanisms of charge injection at the electrode/tissue interface. Faradaic and non-Faradaic charge transfer mechanisms are presented and contrasted. An electrical model of the electrode/tissue interface is given. The physical basis for the origin of electrode potentials is given. Various methods of controlling charge delivery during pulsing are presented. Electrochemical reversibility is discussed. Commonly used electrode materials and stimulation protocols are reviewed in terms of stimulation efficacy and safety. Principles of stimulation of excitable tissue are reviewed with emphasis on efficacy and safety. Mechanisms of damage to tissue and the electrode are reviewed. © 2004 Elsevier B.V. All rights reserved.
Keywords: Efficacy; Electrode; Interface; Protocol; Safety; Stimulation

Contents 1. Physical basis of the electrode/electrolyte interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.1. Capacitive/non-Faradaic charge transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .