Microneurography for the recording and selective stimulation of afferents: an assessment.

The purpose of this study was to examine whether a microneurography electrode could record from and then selectively stimulate the same afferent fiber in cat sural and tibial nerves. Fiber activity was recorded distally with microneurography needle electrodes and proximally with hook electrodes. Records from the hook electrodes allowed the waveform shape and latency following natural stimulation to be compared with that produced by electrical stimuli delivered through the needle electrode. The action potentials from approximately 50% of the recorded fibers failed to propagate beyond the needle electrode. When propagation did occur and the comparison could be made, only 25% of the afferents recorded could be selectively stimulated. This relatively low success rate suggests that a typical microneurography needle is not particularly good for selectively stimulating identified afferents. Thus in human experiments, attempts to microstimulate identified afferents may often include stimulation of unidentified alternative, or additional, afferent fibers at thresholds of sensory perception.