SINGLE-FIBER ACTION-POTENTIALS IN SKELETAL-MUSCLE RELATED TO RECORDING DISTANCES

Single muscle fibre action potentials (SFAPs) are considered to be fun ctions of a bioelectrical source and electrical conductivity parameter s of the medium. In most model studies SFAPs are computed as a convolu tion of the bioelectrical source with a transfer function. Calculated peak-to-peak amplitudes of SFAPs decrease with increasing recording di stances. In this paper an experimental validation of model results is presented. Experiments were carried out on the m. extensor digitorum l ongus (EDL) of the rat. Using a method including fluorescent labelling of the active fibre, the distance between the active fibre and the re cording electrode was derived. With another method, the decline of the peak-to-peak amplitude of SFAPs detected along a multi-electrode was obtained. With both experimental methods, in general peak-to-peak ampl itudes of SFAPs decreased with increasing recording distances, as was found in model results with present volume conduction theory. However, this behaviour was not found in all experiments. The rate of decline of the peak-to-peak amplitudes with recording distance was always less than in models.