Transmission of information by the axon: I. Noise and memory in the myelinated nerve fiber of the frog

One end of the frog sciatic nerve was stimulated with a pair of short pulses and the two action potentials arriving at the other end were recorded from a single fiber. The interval between the two stimuli (stimulus interval) was defined as the input to the channel. The interval between the two action potentials arriving at the other end of the nerve (response interval) was defined as the output of the channel. Repeated stimulation with a constant stimulus interval resulted in a population of response intervals. In the range between the absolute refractory period and 5 msec, the mean response interval was longer than the stimulus interval. In the range between 5-120 msec the mean response interval was shorter than the stimulus interval. This relation depended also on the "history" of the axon and intense activity tended to increase the difference. For intervals longer than 120 msec, the mean response interval was equal to the stimulus interval. The "noise" of the transmission along the axon was approximately Gaussian. At stimulus strength which was well above threshold only few μsec of uncertainty were added along 10 cm of the axon.