Subfascicle stimulation selectivity using a FINE

The Flat Interface Nerve Electrode (FINE) is an attempt to improve nerve cuff stimulation selectivity by elongating the nerve in cross section. This increases the surface area of the nerve, and axons in the neural interior are moved closer to the surface. It has been shown previously that it is possible to select individual fascicles for activation using this electrode. Furthermore, modeling studies have shown that, with further reshaping, it may be possible to independently activate small subpopulations of axons within individual fascicles. In order to test this hypothesis, however, a technique is required to assess this level of selectivity noninvasively, so that the performance of the electrode can be monitored over months. In this work, a technique has been developed to determine whether groups of axons within an individual fascicle can be selectively stimulated based on isometric torque generation in the cat ankle joint. This technique does not injure the animal, so that measurements can be performed chronically. Furthermore, it has been demonstrated that the FINE, even in an acute setting, is capable of selectively activating subpopulations of fibers within individual fascicles