Volume-conducted or "far-field" compound action potentials originating from the intrinsic-hand muscles

When a recording electrode is situated at a relatively far and roughly equal distance from multiple muscle action potential (MAP) sources such as the intrinsic-hand muscles (far-field recording), the individual MAPs generated by muscle fibers may contribute to the resultant compound potential with nearly equal weights depending on the orientation of the individual MAP fields. This is in contrast to recording MAPs directly over the muscle (near-field recording), in which the resultant potential primarily reflects the MAPs that were near the recording electrode. Far-field recorded compound MAPs(CMAPs) thus may provide another dimension or perspective into viewing the overall spatio-temporal relationship among MAPs generated by a large number of muscle fibers. In this study, we described CMAPs from intrinsic-hand muscles that were recorded at a distance from their potential sources.