1. Stimulation and Recording Electrodes: General Concepts

In prosthetic devices, electrodes are the interfaces between the implant system and the body. Electrodes may be used for neural stimulation or neural signal recording according to the application. The signals to be recorded are typically small, i.e. some tens of microvolts for single pulse activity to a maximum amplitude of around 80 mV for intracellular potentials measured for example by fine-tipped electrolyte-filled glass micropipettes in cognitive studies in brain machine interface. On the opposite, neural stimulation sometimes needs relatively high electrode voltages and current densities, sometimes as high as several volts, so it may lead to a high enough energy transfer triggering chemical reactions that involve corrosion and changes in electrode properties.