The intraneural electrical stimulation of human median nerve: a simulation study

Restoring tactile sensations in upper limb neuro-prosthetic users is an important challenge to improve amputee quality of life. Neural prostheses are based on neural interfaces that allow delivering direct stimuli to the nerve fibers. Different kinds of neural electrodes, characterized by different properties as regards geometry or current stimulation parameters, were proposed in the literature. Studying the interaction between electrode stimulation and nerve fibers is fundamental for evaluating its ability to activate axon fibers and the electric potential distribution in the nerve. In this paper, the ds-FILE electrode is considered in the FEM simulation to study its interaction with the nerve fibers. The results can be very useful for the advancement of more realistic tactile sensations in amputee subjects from two point of view: the efficacy of the stimulation, that is related to the activation of axons subjected to the electrical stimulation, and the safety of the stimulation, related from a first consideration to the current intensity and waveform used. So in this paper are considered the results of three type of waveform that are the more safety as reported in literature [1] and they are comparedThe research aims to study, by means of a FEM-Neuron computational model, the axon fibers activation by means of the intraneural stimulation using different types of stimulus waveforms. The obtained results show that, using a biphasic charge unbalanced stimulus, the threshold to activate all the fibers considered in a location near an active site of the electrode is lower than the threshold found using biphasic charge balanced stimuli. This is an important result because the stimulation is equally efficient using low current amplitude.