Relationship between the location of the ground electrode and size of electrical stimulus artifacts

In simulated electrophysiologic recordings, electrical stimuli were applied to the upper limbs of ten subjects. Then, stimulus artifacts were recorded using different ground locations, while all other technical parameters were kept constant. Stimulus artifacts were relatively large (often reaching a maximum amplitude) when stimulating electrodes were between ground and recording electrodes. Artifacts were relatively small (commonly arriving at a minimum and never at a maximum value) when recording electrodes were between ground and stimulus sites. When the ground was situated between stimulating and recording electrodes, the stimulus artifacts had about an even chance (40-50%) of achieving either a maximum or a minimum amplitude value. These findings do not seem to support the traditional belief that the best ground location to reduce the size of the stimulus artifacts is between points of stimulation and recording.