Study of electrical neural stimulation effects using extraneural and intraneural electrodes

Background: Sensory feedback restoration in upper limb neuroprosthetics can importantly contribute to improve life conditions of amputees. Neural interfaces allow eliciting sensory information through current stimuli. Stimulation studies can be useful to evaluate the electric potential distribution into the nerve in response to a current stimulus and therefore fibers activation. In this paper, hybrid FEM-Neuron computational models are used to study nerve fibers activation in different nerve models resembling the human median nerve. Results: To have a comprehensive study, the variability in fascicles topography and different configurations of active sites of two types of electrodes (intraneural and extraneural) have been considered. Furthermore, the simulation results (in terms of fibers percentage of activation in nerve fascicles, their location into the nerve section models and the order of their activation when the stimulus increases) are evaluated according to the sensation intensity perceived by a human amputee in experimental trial. Conclusions: The obtained results let us to infer: i) the impact of the use of intraneural and extraneural electrodes on the number, and position of activated fascicles when the minimum values of electric charge considered in the experimental trial are used; ii) the dependence of the order of fibers activation into the fascicles from the current stimulus.