A NONINVASIVE STRATEGY FOR IDENTIFYING AND QUANTIFYING INNOCUOUS AND NOCICEPTIVE PERIPHERAL AFFERENT ACTIVITY EVOKED BY NERVE-STIMULATION

This study evaluated the utility of the compound nerve action potentia l (CAP) and spinal nociceptive withdrawal (R3) reflex in identifying a nd quantifying peripheral afferent activity evoked by sural nerve stim ulation in humans. The results of this work demonstrate that currents less than or equal to that which elicits a just-maximal CAP can be con sidered purely innocuous; provide further evidence that the R3 is an o bjective means of identifying noxious stimulus levels; and suggest tha t current provides the best noninvasive quantitative estimate of affer ent activity throughout the innocuous and noxious range. This work als o demonstrates that some of the individual variability in the psychoph ysical function can be attributed to peripheral factors that affect th e amount of current reaching the nerve. It is important, therefore, th at these peripheral factors be considered when studying individual dif ferences in the psychophysical function generated by electrical stimul ation.