Fig. 1

Overview of experimental methods to measure the characteristics of KHF block. A Experimental preparation of tibial nerve block in an anesthetized rat. Red crosses indicate transected nerve branches. The electrodes used for KHF signals were either monopolar, bipolar, or tripolar (one cuff type per rat). B Initial set of frequencies applied during frequency tests in each experiment. C Composite signal construction for composite signal tests. We constructed each composite signal by superposing a sinusoid of frequency f₀ with a sinusoid of frequency 2f₀, where f₀ was a nerve-specific fundamental frequency. We scaled the f₀ and 2f₀ sinusoids by different relative amplitudes (amplitudes of sin(θ) and cos(θ), respectively, where θ is the inclination). We shifted the phase of the second harmonic (azimuth, φ) to produce distinct composite signal shapes. D Plot of the range of azimuth and inclination values used across experiments. Example composite signals are shown for color-coded circled data points. The azimuth and inclination values were uniformly spaced in the spherical φ and θ space. E Timing of each KHF trial. F Sample output force recorded from a single KHF trial. Gray boxes indicate force responses used for calculation of stimulation-triggered median force responses. G Example stimulus-triggered median where block did not occur (i) and where partial block occurred (ii). The degree of block during the KHF signal was established almost immediately upon starting the KHF signal, with some variability in twitch amplitude during the KHF signal. The 6 s waiting period allowed any onset responses to subside before quantifying the state of block