CONCENTRIC AND SINGLE-FIBER ELECTRODE SPATIAL RECORDING CHARACTERISTICS

A better appreciation of the specific spatial recording characteristic s of the single fiber and concentric needle electrode can result in mo re accurate physiologic and theoretical interpretations of single fibe r and quantitative motor unit action potential analysis. We demonstrat e by physical modeling that the 90% and 99% amplitude sensitivity enve lopes are not simple hemispherical shapes, The 90% sensitivity concent ric electrode volume does not extend beyond the insulated portion of t he 15 degrees beveled surface between the core and cannula and extends only 280 mu m perpendicularly from the center of the core's surface. The 99% envelope extends approximately 830 um perpendicularly from the core's center, This is a much smaller volume of sensitivity than exis ts for a similarly modeled monopolar electrode. The 90% and 99% envelo pes extend to 110 and 320 mu m perpendicularly from the exposed single fiber core. Both the single fiber and concentric needle volumes of se nsitivity have specific asymmetries described. (C) 1997 John Wiley & S ons, Inc.