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PubMed2001

Selective stimulation of cat sciatic nerve using an array of varying-length microelectrodes.

Restoration of motor function to individuals who have had spinal cord injuries or stroke has been hampered by the lack of an interface to the peripheral nervous system. A suitable interface should provide selective stimulation of a large number of individual muscle groups with graded recruitment of force. We have developed a new neural interface, the Utah Slanted Electrode Array (USEA), that was designed to be implanted into peripheral nerves. Its goal is to provide such an interface that could be useful in rehabilitation as well as neuroscience applications. In this study, the stimulation capabilities of the USEA were evaluated in acute experiments in cat sciatic nerve. The recruitment properties and the selectivity of stimulation were examined by determining the target muscles excited by stimulation via each of the 100 electrodes in the array and using force transducers to record the force produced in these muscles. It is shown in the results that groups of up to 15 electrodes were inserted into individual fascicles. Stimulation slightly above threshold was selective to one muscle group for most individual electrodes. At higher currents, co-activation of agonist but not antagonist muscles was observed in some instances. Recruitment curves for the electrode array were broader with twitch thresholds starting at much lower currents than for cuff electrodes. In these experiments, it is also shown that certain combinations of electrode pairs, inserted into an individual fascicle, excite fiber populations with substantial overlap, whereas other pairs appear to address independent populations. We conclude that the USEA permits more selective stimulation at much lower current intensities with more graded recruitment of individual muscles than is achieved by conventional cuff electrodes.

Animals↗

PubMed2000

A multielectrode array for intrafascicular recording and stimulation in sciatic nerve of cats.

The feasibility of implanting an array of penetrating electrodes into peripheral nerves is studied in acute experiments in the cat sciatic nerve. A novel, silicon-based array of microelectrodes, the Utah Electrode Array, was used, which contains 25 or 100 1-mm long electrodes that project out from a silicon substrate. Electrode arrays of this complexity, when inserted in the peripheral nerve, could cause significant compression of the nerve and block the conduction of action potentials. Using a high velocity insertion technique, the electrode array was implanted into the sciatic nerve. Compound action potentials were evoked by and recorded with cuff electrodes. Compound action potentials recorded 1 h after insertion were only slightly altered from those recorded before insertion. Single units were readily extracted from evoked multiunit neural recordings in response to cutaneous stimulation and limb rotation around joints. Current injections into the nerve through the electrodes evoked muscle twitches with currents in the 10 microA range. Recording and stimulation stability were demonstrated for periods of up to 60 h. We have shown that high density arrays of electrodes can be inserted into the peripheral nerve and can provide a stable recording and stimulating interface to individual peripheral nerve axons. Such an array may be useful in future neuroscience research and potential neuroprosthetic applications.

Action Potentials↗