J.H. Meier

Force recruitment during electrical nerve stimulation with multipolar intrafascicular electrodes

Experimentally, during electrical nerve stimulation, the influence is examined of two intrafascicular anodes on the force recruitment with one intrafascicular cathode. It is found that the anodes suppress recruitment and that this effect is more pronounced when the distance of the anodes to the cathode is decreased, or when the anodal currents are increased. The measured recruitment curve patterns can be qualitatively explained by a nerve stimulation model that calculates theoretical recruitment curves for intrafascicular multi-electrode configurations. Discrepancies between the experimental and the theoretical recruitment curves are seen, but these can be understood by taking into account a non-uniform fibre distribution.

Intraneural recording for neuroprosthetic use: normal action potential shapes and blocking effects

For neuroprosthetic use of afferent activity, model results and experimental recordings of action potentials (aps) made with tungsten micro electrodes in rat peroneal/sural nerve are presented and compared. The model shows that the normal shape can be as well biphasic as triphasic, depending on extraneural conductivity. In the experiments, five classes of ap shapes are observed, of which two are seen in the model too; part of the other shapes may be tentatively ascribed to propagation-block or propagation-start phenomena.

Selectivity of recording of neural signals with micromachined intraneural multi electrodes

The number uf afferent fibers in a peripheral nerve fascicle and the electrical volume conduction in neuraI tissue determine the interelectrode spacing, needed for selective recording with mufticontact devices. These factors taking into account, and also assuming uniform distribution of fibers throughout the fascicle cross section, it is calculated that for selective sensing in peroneal nerve fascicles, the electrode spacing must be about 80 pm. This is for the nelve, embedded in its natural saline environment. The selectivity, thus reached, however reduces dmstically to zero when an insulating cuff is positioued around the nerve at the position of the intraneural multielectrode device.

Multipolar intrafascicular stimulation

The suppressing effect of two intrafascicular anodes on the neural recruitment elicited by one intrafascicular cathode has been studied. Recruitment curves are calculated with a nerve stimulation model and are compared to experimental curves for the peroneal nerve of rat.