Ion mechanism and parameter analysis of anodal-first waveforms for selective stimulation of C-fiber nerves

Few investigations have been conducted on selective stimulation of small-radius unmyelinated C nerves ( C ), which is critical to both recoveries of damaged nerves and pain suppressions. The purpose of this study is to understand how an anodal pulse in an anodal-first stimulation could improve C -selectivity over myelinated nociceptive Aδ nerves ( Aδ ), and further clarify the landscape of the solution space. The Hodgkin-Huxley (HH) model and the Mclntyre-Richardson-Grill (MRG) model were used for modelling C and Aδ, respectively to analyze the underlying ion dynamics and the influence of relevant stimulation waveforms, including monopolar, polarity-symmetric, and asymmetric pulses. Results showed that polarity-asymmetric waveforms with preceding anodal stimulations benefit C -selectivity most, underlain by the decrease of the potassium ion current of C . The optimal parameters for C -selectivity have been identified in the low frequency band, which will benefit remarkably the designs of nociceptive nerve selective stimulation.