Modeling the excitation of fibers under surface electrodes.
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Action Potentials↗
Biomedical subjects
F Rattay
Publications and source records attributed to F Rattay.
Ways to approximate current-distance relations for electrically stimulated fibers.
The behaviour of myelinated and unmyelinated fibers is simulated by a model for extracellular stimulation in order to confirm current-distance phenomena known from experiments. Lower and upper limits for cells stimulated with cathode current are calculated for unmyelinated fibers. In the case of myelinated fibers the threshold depends on the distance from the axon and from the nodes.
Electric Stimulation↗
Simulation of the response of a multichannel nerve array to pulse shapes produced by single-channel electrostimulation.
Results of experiments on single-channel electrostimulation of the cochlea which throw light on the performance of the central auditory nervous system (CANS) have recently been reported by Dobie and Dillier. Trains of pulses with different rise times could be distinguished by subjects with cochlea implants, even though time differences involved were very small. It was suggested by the authors that the information is carried to the CANS by an array of nerve fibres with characteristic time differences. In the present paper, simulations produced by means of a nerve model are reported and used to compute the patterns of action potentials evoked on the nerve array by different pulse trains. The changes in the patterns of the nerve responses resulting from the shape variations which have to be perceived by the CANS are examined.
Cochlear Implants↗
Signal processing strategies for electrostimulated ear prostheses based on simulated nerve response.
Improvements to the coding strategy of prostheses for the profoundly deaf which can be implemented by the speech processors of these devices are suggested. Difficulties with vowel recognition are diagnosed as being due to nerve properties. These are studied with the aid of a model in order to find ways of overcoming the difficulties.
Cochlear Implants↗
High frequency electrostimulation of excitable cells.
Reactions of nerve fibers to high frequency electrical stimulation are examined with three nerve models. Switching on the signal produces a single AP at the threshold current. Stronger currents lead into a region of repetitive firing. The firing rate depends on the current and the fibers more distant from the electrode will have a lower rate. The AP's are not synchronized. In the "House-Urban" cochlear implant a 16 kHz carrier is used for stimulation. It is modulated by electrical signals derived from sound pressure. An analysis of the modulation shows which signals can produce APs synchronized with the source signal.
Animals↗
A study of the application of the Hodgkin-Huxley and the Frankenhaeuser-Huxley model for electrostimulation of the acoustic nerve.
By means of electrostimulation of the acoustic nerve profoundly deaf patients can, in the best cases, reach almost complete speech understanding without lip reading. In this paper the information content of the signals supplied to patients is examined by a study of action potential generation by means of the Hodgkin-Huxley and the Frankenhaeuser-Huxley equations solved by means of a digitally controlled analogue computer. The response to sinusoidal signals and to signals with the wave shape of certain vowels is investigated and compared with results from animal experiments and observation on patients.
Action Potentials↗
Analysis of models for external stimulation of axons.
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Animals↗
A model for the electrostimulation of the nervus acusticus.
Electrostimulation of the nervus acusticus has been successfully used to achieve speech understanding. A model of nerve excitation due to Fitzhugh [(1961) Biophys. J. 1, 445-446] has been explored to show that the stochastic response of single acoustic mammalian fibers observed by Rose, Brugge, Anderson and Hind [(1967) J. Neurophysiol. 30, 769-793] may be due to the non-linear interaction of sub-threshold electrical nerve activity with the signal. Computations by means of an analogue computer also shows that a phase-locked response with a frequency dependence resembling behaviour observed with electrostimulation is obtained with the model. A dynamic range for single fiber excitation is produced by the non-linear interaction.
Cochlear Implants↗
[Quantitative assessment of electrically activated fiber populations exemplified by rotating stimulation].
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Electric Stimulation Therapy↗
[Treatment of hyperemesis gravidarum by electrostimulation of the vestibular apparatus].
26 patients hospitalized with Hyperemesis Gravidarum were treated with electrical stimulation of the vestibular system, as the symptoms of Hyperemesis Gravidarum resemble the symptoms of motion sickness, where the electrical stimulation has been used successfully. The patients were treated for one hour daily, two hours before the standard infusion therapy. 89% reported a decrease in vomiting and nausea during the first application, 85% a lasting improvement. Theoretical considerations concerning the mechanism of the effect are discussed.
Adult↗