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1.
IEEE Trans Biomed Eng ; 38(2): 192-8, 1991 Feb.
Article in English | MEDLINE | ID: mdl-2066129

ABSTRACT

Artificial electrical stimulation of peripheral nerves needs the development of multielectrode devices which stimulate individual fibers or small groups in a selective and sensitive way. To this end, a multielectrode array in silicon technology has been developed, as well as experimental paradigms and model calculations for sensitivity and selectivity measures. The array consists of twelve platinum electrode sites (10 x 50 microns at 50 microns interdistance) on a 45 microns thick tip-shaped silicon substrate and a Si3N4 insulating glass cover layer. The tip is inserted in the peroneal nerve of the rat during acute experiments to stimulate alpha motor fibers of the extensor digitorum longus muscle. Sensitivity calculations and experiments show a cubic dependence of the number of stimulated motor units on current amplitude of the stimulatory pulse (recruitment curves), starting at single motor level. Selectivity was tested by a method based on the refractory properties of neurons. At the lowest stimulus levels (for one motor unit) selectivity is maximal when two electrodes are separated by 200-250 microns, which was estimated also on theoretical grounds. The study provides clues for future designs of two- and three-dimensional devices.


Subject(s)
Electrodes , Peripheral Nerves/physiology , Silicon , Animals , Electric Stimulation/instrumentation , Equipment Design , Peroneal Nerve/physiology , Ranvier's Nodes/physiology , Rats , Recruitment, Neurophysiological/physiology , Sensitivity and Specificity
2.
Electroencephalogr Clin Neurophysiol ; 73(3): 245-53, 1989 Sep.
Article in English | MEDLINE | ID: mdl-2475329

ABSTRACT

In vivo records of single fibre action potentials (SFAPs) have always been obtained at unknown distance from the active muscle fibre. A new experimental method has been developed enabling the derivation of the recording distance in animal experiments. A single fibre is stimulated with an intracellular micropipette electrode. The same electrode is used thereafter for labelling with an auto-fluorescent dye, Lucifer Yellow. In this method there is no use of chemical fixation. The tissue structure is kept as well as possible. In cross-sections the fluorescent fibre is seen and its position is quantitized with respect to the tip of one or more recording wire electrodes. Morphometric data, such as the recording distance and the fibre cross-sectional area, are used for the interpretation of parameters of the SFAPs (peak-peak amplitude, time between the first positive and negative peaks). The present results show that within 300 microns recording distance is not as dominant for the SFAP shape as expected. The method offers also a direct check of the relation between the muscle fibre; diameter and the conduction velocity of the action potential. In the present small set of data there is no simple linear relationship.


Subject(s)
Muscles/physiology , Action Potentials , Animals , Electric Stimulation , Electromyography/methods , Forelimb , Male , Muscles/cytology , Neural Conduction , Rats , Rats, Inbred Strains
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