Intraneural Stimulation using Wire-Microelectrode Arrays: Analysis of Force Steps in Recruitment Curves

In acute experiments on six Wistar rats, a wiremicroelectrode array was inserted into the common peroneal nerve. A 5-channel array and a 24-channel array were available. Each electrode in the array was used to generate a twitch contraction force recruitment curve for the extensor digitorum Longus muscle. We constructed a histogram of the pooled force steps in all recruitment curves. From a comparison of this experimental histogram with one estimated from literature data, we found that the force steps encountered in our experiments are in the same range as those from the literature-based estimated distribution. Discrepancies between the experimental and the literature-based histogram might be ascribed to an approximation used in the estimated distribution. We conclude that force step histograms appear to provide a simple means for estimating motor unit twitch force distributions, and thus are of value in studies of intraneural selective stimulation.