An objective method for assessing graded electrically evoked afferent activity in humans

A problem arises in human sensorimotor studies when attempts are made to equate the intensity of electrical stimulation of a peripheral nerve with the amount of afferent activity generated. Results presented here reveal that sural recruitment curves exhibit large session to session differences both within and among subjects. These differences hinder the prediction of afferent activation based solely upon stimulus intensity. An alternative method based upon measurement of the evoked potentials is described for improving on these predictions. Sural nerve stimulation is used to demonstrate this method, but the method should be applicable wherever a peripheral nerve is accessible for electrical stimulation and evoked recordings.