Comparison of Fiber Diameter Distributions Deduced by Modeling Compound Action Potentials Recorded by Extracellular and Suction Techniques

In this study, the extracellular and suction techniques, used widely to record compound action Potentials (CAP), were compared in respect to their ability to deduce fiber diameter distribution (FDD). Fiber. diameter distribution derived by applying the deconvolution model to CAP depends not only on the modeling but also on the recording techniques. The FDDs determined by these two techniques were compared with that predicted by histological means. In our model study, a waveform for single fiber action potential (SFAP) was defined as f(t) = Asin(t/tau(01)) . exp(-t/tau(02)) where the parameters tau(1) and tau(2) were taken from the literature and given for the SFAP of each fiber diameter between d = 3-22 mum, and A Was chosen to normalize the amplitude of SFAP to 1. We substituted the measured CAPs into our model and calculated the histograms related with the fiber diameter distribution of the sciatic nerve trunk. We sail, that the FDD as predicted from the CAP, recorded by the extracellular techniques, coincides better with that of the histologically determined FDD than that predicted by suction techniques.