Effects of changes in asymmetry, duration and propagation velocity of the intracellular potential on the power spectrum of extracellular potentials produced by an excitable fiber
Dimitrov, G.V.; Lateva, Z.C.; Dimitrova, N.A.
Electromyography and Clinical Neurophysiology 28(2-3): 93-100
1988
ISSN/ISBN: 0301-150X PMID: 3416810 Document Number: 324674
Changes in the power spectrum density function (PSDF) of extracellular potentials (EPs) produced by an unmyelinated nerve fiber were theoretically studied under variation of the asymmetry, duration (Tin) and propagation velocity (PV) of the intracellular action potential (AP). It was found that the changes in the power spectrum under variation of the parameters mentioned above, depend on the radial distance of the observation point from the fiber axis. At small radial distances the distribution of the power spectrum density (DPSP) is practically independent of PV, but it is shifted to the lower or higher frequencies approximately proportionally to the increase or decrease in Tin, respectively. Variations in the intracellular AP asymmetry (the total duration of the intracellular AP being unchanged) mainly result in changes in the higher-frequency components. At great radial distances the DPSD depedns on PV and is practically independent of the asymmetry and duration of the intracellular AP. At medium radial distances all the parameters affect the power spectrum. Advantages and shortcomings of different ways of power spectrum representations are discussed. Possible sources of power spectrum misinterpretations are pointed out.