Measuring conduction velocity distributions in peripheral nerves using neurophysiological techniques

Objective To determine how long it takes for neural impulses to travel along peripheral nerve fibers in living humans. Methods A collision test was performed to measure the conduction velocity distribution of the ulnar nerve. Two stimuli at the distal and proximal sites were used to produce the collision. Compound muscle or nerve action potentials were recorded to perform the measurements on the motor or mixed nerve, respectively. Interstimulus interval was set at 1–5 ms. A quadri-pulse technique was used to measure the refractory period and calibrate the conduction time. Results Compound muscle action potential produced by the proximal stimulation started to emerge at the interstimulus interval of about 1.5 ms and increased with the increment in interstimulus interval. Two groups of motor nerve fibers with different conduction velocities were identified. The mixed nerve showed a wider conduction velocity distribution with identification of more subgroups of nerve fibers than the motor nerve. Conclusions The conduction velocity distributions in high resolution on a peripheral motor and mixed nerve are different and this can be measured with the collision test. Significance We provided ground truth data to verify the neuroimaging pipelines for the measurements of latency connectome in the peripheral nervous system.