T.A. Frieswijk

Force-current relationships in intraneural stimulation: role of extraneural medium and motor fibre clustering.

Animal experiments and model simulations of monopolar, intrafascicular nerve stimulation are presented to study force-current relationships (recruitment curves). The conductivity of the extraneural medium is of prime importance to the resulting recruitment curves: an insulating extraneural medium generally leads to steeper curves with lower threshold currents than a well-conducting extraneural medium. Extensive statistical comparison of experimental and model results suggests the occurrence of clustering of α-motoneurons within the fascicle, manifesting itself mainly by an increased spread in threshold currents, as opposed to the situation where the fibres are distributed uniformly throughout the entire fascicle.

Control electronics for a neuro-electronic interface implemented in a gate array

Presents a Gate Array for implementing electronic circuitry to control multi-electrode arrays, which consist of 128 microelectrodes. The chip contains multiplexers, current sources and buffer amplifiers in CMOS technology.

The influence of nerve fiber distribution on the recruitment behavior resulting from intraneural stimulation

Force recruitment cumes have been recorded for the rat extensor digitorum longus muscle (EDL) using monopolar stimulation with intraneural wire electrodes. The recruitment curves vary with the position of the electrode in the nerve This has implications when intraneural stimulation techniques are used to precisely control muscle force. To assess this effect, two parameters were extracted for each recruitment cuwe: the threshold current and the slnpe in the low-farce range. When these experimental parameters are compared with the same parameters resulting from simulated recruitment curves, it becomes clear that the low density of nodes of Ranvier and the degree of clustering of nerve fibers are of major importance for the recruitment behavior resulting from intraneural stimulation. It is also shown that the external medium conductivity σe, is an important parameter influencing the recruitment behavior.

The effect of spatial clustering of motor fibers in a nerve fascicle on force recruitment during electrical stimulation

Force recruitment curves have been determined using stimulation with an intraneural wire electrode. The recruitment curves vary with the position of the electrode in the fiber bundle. The results seem to support previous findings which indicated that the low density of nodes of Ranvier and a possible clustering of motor fibers within the fiber bundle might have a major impact on the efficacy of intraneural electrical stimulation.

Strategy for control of muscle force using a 3D multi electrode array in intraneural stimulation

A control algorithm for regulation of the force produced by the rat EDL muscle is presented, using a 128-electrodes intraneural stimulation device. The algorithm is based on force regulation in nature; its task is basically to find a combination of rate coding and recruitment to produce a required force, keeping fatigue minimized. The algorithm was tested in a simulated environment, with satisfactory results.