THE APPARENT DISTORTION OF BRIEF RECTANGULAR ELECTRICAL STIMULI IN NERVE

If it is assumed that the kinetics of the process of excitation in nerve is given by dp/dt = KI – kp, I being the actual exciting component of the current, p the state of excitation, and K and k constants, it is necessary to postulate that on application of a rectangular stimulus of voltage, V, the current, I, undergoes a transient exponential variation, usually a decrease, in order that the integral of the differential equation (above) may fit the strength-duration data in V and t. This hypothesis is substantiated by data by Sakamoto on single fibers of the sciatic nerve of the frog. The time constant of the postulated current transient is of the order of 10^–4 sec. for single fibers and of the order of 10^–5 sec. or less in the sciatic nerve trunk. The latter value is about the same as that found by Cole in the same tissue by purely physical measurements. Some criticisms by Rushton (1934) are discussed.