Introduction to Volume Conduction

Abstract

The term “volume conduction” refers to the complex effects of measuring electrical potentials a distance from their source generators. Near-field potentials refer to those recorded in relative close proximity to the detector, whereas far-field potentials refer to those recorded at a considerable distance, as is most commonly the case in evoked potentials. A relative straightforward model of volume conduction can be worked through to assist in better understanding how volume conduction effects can impact the shape of a recorded neuronal potential. In fact, all motor and sensory nerve conduction waveforms are substantially impacted by volume conductive effects. The recording setup of sensory studies (i.e., whether they are bipolar or referential) also impacts the size and morphology of the recorded signals. In addition, the compound motor action potential actually represents a composite of both near- and far-field activity. The morphology of both spontaneous discharges and the motor unit potentials themselves evaluated during needle EMG are, in part, caused by the complex effects of volume conduction.