A study of the motor unit action potential by means of computer simulation

Abstract

Abstract. In order to study the motor unit action potential a computer simulation model was developed. It is based on the superposition of single muscle fibre potentials of the fibres belonging to the motor unit. The parameters which characterize each fibre (spatial position, diameter, and a dispersion of arrival time of the potential at the electrode) are chosen from statistical distributions which can be derived from anatomical and physiological data. The electrode type, position and dimensions can be specified. Simulated motor unit action potentials are presented in the time and frequency domain. The simulation results refer to (1) the influence of the electrode position and dimensions with respect to the motor unit territory, (2) the meaning of this model for the study of pathological phenomena, (3) the variability of some parameters characterizing the motor unit, (4) the selectivity of uni-and bipolar electrodes and finally (5) the influence of the geometrical situation of the motor end-plates within the muscle, on the shape of motor unit action potentials.

Evidence of Potential Averaging over the Finite Surface of a Bioelectric Surface Electrode

“…4,5,[7][8][9]11 It should be noted, however, that such studies do not provide evidence to support this assumption, since the skin-electrode interface properties are not taken into account. In related application fields, the electrode has been modeled more precisely and the impedance between the electrode and the skin has been explicitly considered.…”

Calculation and registration of the same motor unit action potential

“…This kind of model has been proposed before (e.g,, Dimitrova and Dimitrov 1974;Boyd et al 1978;Griep et al 1978;Wani and Guha 1980). The essential aspect added in this paper is the direct comparison of the measured and calculated action potentials of motor units of which all the muscle fibre positions have been determined.…”

“…If only global structures of motor units are taken into account, it is difficult to interpret recorded MUAPs. Some models are based on merely statistical descriptions (George 1970;LindstrSm and Broman 1974: thesis LindstrSm, Chalmers University of Technology, GSteborg 1974), some are based on specific arrangements of muscle fibres (Boyd et al 1978;Dimitrov 1978a, b;Griep et al 1978;Wani and Guha 1980). In our opinion the models which are based on realistic arrangements of muscle fibres are most promising for interpreting MUAP shapes and in order to verify this idea a special experiment was carried out.…”

Novel Ideas for Fast Muscle Action Potential Simulations Using the Line Source Model

“…Approximating the cylindrical recording surface with a thin wire of length , the weighting functions of the macro electrode and the CN cannula are the average over its length [9], [24] (see Fig. 6).…”

“…Various approaches to this accuracy/complexity tradeoff have been presented [9]- [16]. By lumping the transmembrane current to the center of the muscle fiber, the line source model is obtained which describes the AP as a convolution of a weighting function and the transmembrane current [13].…”