Effect of the nerve fiber path eccentricity on the single fiber action potential

The relative position of an indwelling electrode to the nerve fiber plays a critical role in the shape of the single fiber action potential (SFAP) detected by the electrode. Parameters such as electrode to fiber distance, fiber path, and position of the nodes of Ranvier can have a substantial influence on the shape and frequency content of the SFAP. This study explores the effects of these parameters on the shape of simulated SFAPs within a nerve bundle with a thin-film Longitudinal Intrafascicular Electrode (tfLIFE) longitudinally implanted at the midline of a 2.4 mm diameter nerve fascicle. The SFAPs were calculated for various distances, fiber paths and nodal offsets for a 10 μm caliber myelinated fibers. The correlation coefficient was used to quantify the changes in the SFAP shape. It was found that all parameters play a role in changing the SFAP shape. The nodal offset was found to have the greatest effect, altering the correlation coefficient nearly 0.2 from the reference SFAP. Knowing that the parameters have such an effect on the SFAP shape has lead to the conclusion that fiber distance, path and nodal offset has the potential of allowing the extraction of nerve fiber locations relative to the electrode structure.