2022 Volume 50 Issue 1 Pages 7-14
A frequency-dependent conduction block is a phenomenon whereby the amplitude of a compound action potential decreases as its frequency increases. In general, we observe a conduction block when the safety factor of transmission, which is defined as the ratio of driving current to threshold current, is less than 1. Many researchers have inferred that frequency-dependent conduction block can be observed because the denominator of the safety factor, which is the threshold current, increases with increasing frequency. However, it can also cause frequency-dependent conduction block that the numerator, which is the driving current, decreases with increasing frequency. Recently, I have modified the cable theory by considering the axon to be made up of a mixture of conductor and insulator, rather than pure conductor, with the notion of dielectric dispersion. The modification allows us to predict that the amplitude of current along an axon can decrease as its frequency increases. The current along an axon is the driving current, which is the numerator of the safety factor. Therefore, by applying the modified theory to conduction block phenomenon, we can easily understand how frequency-dependent conduction block occurs.
