Integral characteristics of extracellular single fibre action potentials.

The changes in the integral of the extracellular action potentials (EAPs) generated by an infinite homogeneous fibre in an infinite homogeneous and isotropic volume conductor were studied at different radial distances (yo) from the fibre axis, depending on the propagation velocity (v), duration (Tin) and asymmetry of the intracellular action potential (IAP). The method used was a mathematical modelling. It was obtained that: the EAPs generated by an infinite fibre have no DC component, i.e. the integral value of the negative phase (INPh) is equal to that of the two positive phases (IPPh); the character of the integral dependences is different at different radial distances; INPh is related both to the EAP amplitude and to the temporal parameters of the EAP; at small radial distances INPh normalized in respect of the negative phase amplitude is in generally linear relationship with the Tin, it decreases when the IAP asymmetry increases (with the Tin being unchanged), and it is not practically affected by the changes in the yo (up to 0.2 mm) and by the changes in the v; at large yo the normalized INPh is almost inversely proportional to the v and is not practically affected by the changes in the Tin and in IAP asymmetry.