Influences of stimulation conditions on recruitment of myelinated nerve fibres: a model study

The dependency of excitation of myelinated nerve fibres on nerve-fibre diameter, and the geometrical spread of recruited nerve fibres in the fascicle during artificial nerve simulations were investigated by varying parameters of a simulation model presented by P.H. Veltink et al. (ibid., vol.35, p.69-75, 1988). The model predicts that fascicle conductivities and the connective tissue sheath surrounding the fascicle, i.e., the extraneural tissue, together with the radius of the fascicle and the thickness of the connective tissue sheath, influence both recruitment order and geometrical spread of recruited motoneuron fibres in the fascicle. The model predicts recruitment probability to increase for increasing nerve-fibre diameter in the entire, or almost the entire range of stimulation pulse-amplitudes in all simulated cases. In a probabilistic sense, this implies an inverse order of recruitment compared to the physiological order.