A novel electrode array for diameter dependent control of axonal excitability: a simulation study

Electrical extracellular stimulation of peripheral nerve stimulates large diameter fiber before small diameter fiber, which is opposite to the natural recruitment order Ill. This study presents a novel peripheral nerve stimulation technique capable of enhancing the excitability of small myelinated axons and suppressing the excitability of large ones. The mechanism of the technique is to reshape the profile of extracellular voltage along the axon by using an array of electrodes placed along the nerve fiber. The hypothesis was tested using computer simulation. Axons and current sources were assumed to lie in a purely resistive homogeneous isotropic conducting medium. The current excitation threshold as a function of axon diameter was computed using numerical integration. The results from the conventional cathodic stimulus and the electrode array were compared. The results showed that the excitability of certain axon diameter range can be suppressed by an electrode array with a specific interelectrode distance.