Neural stimulation current control

Current introduced to the body is often held to low values by the electrical resistance of dry skin, between 5,000 and 10,000 ohms (Kantrowitz, 1972). Wet skin will have electrical resistance levels as low as one-tenth of this. Where electrical leads are introduced subcutaneously, resistance falls to 10-50 ohms, and this situation is potentially dangerous. Subcutaneous leads are used for heart pacemakers, artificial hearts, transcutaneous electrical neural stimulation (TENS) to block pain, and subdural leads for the control of Parkinson s disease. 

Using a current source for removing the residual charge In this method, a current source discharges the electrodes after stimulation towards the potential of the counter electrode. The current source is preferred to using a switch because the current is fixed and controlled so current spikes which would potentially cause undesired neural stimulation are avoided. 

Electrical Stimulation Devices. Bioelectrodes that transmit electrical signals into the body are generally known as electrical stimulation devices, examples of which include cardiac pacemakers, transcutaneous electronic nerve stimulators (TENs) for pain suppression, and neural prostheses such as auditory stimulation systems for the deaf and phrenic nerve stimulators for artificial respiratory control. In these, and other similar devices, electrodes transmit current to appropriate areas of the body for direct control of, or indirect influence over, target cells. 

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