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Transcranial magnetic stimulation (TMS) is a technique for noninvasive stimulation of the human brain. Stimulation is produced by generating a brief, transient high intensity magnetic field by passing a brief, transient electric current through a magnetic coil placed upon the scalp. The induced electrical currents in the underlying cortical tissue produce a localized axonal depolarization [1-3]. TMS...
The purpose of this paper is to evaluate the response of the spinal cord and nearby area during lumbar magnetic stimulation. One of the most important issues about magnetic stimulation of nervous tissue is the lack of precision in the stimulated region. Based on the experimental measurements performed in cooperation with the Medical University of Vienna, the figure-of-eight coil configuration was...
The technique of magnetic stimulation (MS) of nerve fibers represents a common technique in modern medicine. One of the most important issues regarding the MS of the nervous tissue is represented by the lack of precision concerning the stimulated region. In order to obtain stimulation results as good as possible, the optimization necessity for both the stimulation coil and the electric circuit arises...
This paper aims in estimating which nerve fibers can be activated during magnetic stimulation of the lumbar area of the thorax. For this purpose, we compute the electrical field and the activation function induced in the tissue. We used a simplified model, where the spinal cord is modeled as a continuous cylinder, while the vertebral column is also represented by a concentric interrupted cylinder...
In this paper we present a model that combines circuit analysis with Maxwell's equations of electromagnetic theory and non-linear cable theory, to explain the action of the induced electric field upon a nerve fiber. The current source and stimulating coil are modeled as a series RLC circuit. The induced electric field distribution within a homogeneous cylindrical volume conductor modeling the arm...
Threshold problems in electric stimulation of nerve and muscle fibers have been studied from a theoretical standpoint using the excitation functional. Here the excitation functional is extended to magnetic stimulation of excitable nerve and muscle fibers. A unified derivation of the functional is done, for (non myelinated) nerve and muscle fibers, by means of the nonlinear cable equation with a Fitzhugh-Nagumo...
This paper summarized the basic principle of magnetic stimulation, and established the connection between action potential of neural cell and electrical parameters by simulating the neural model. The simulation of coil electromagnetic field and calculation of circuit mathematical model were also combined to derive out the electrical parameters. They are charging voltage, discharging current, stimulating...
Several recent studies have investigated the mechanisms of repetitive transcranial magnetic stimulation (rTMS) using small animals. However, there is still limited knowledge about the distribution of the induced electric field, and its dependence on coil size, geometry and orientation. In this work we calculate the electric field induced in a realistically shaped homogeneous mouse model by commercially...
A model is presented that predicts the electric field induced in the arm during magnetic stimulation of a peripheral nerve. The arm is represented as a homogeneous, cylindrical volume conductor. The electric field arises from two sources: the time - varying magnetic field and the accumulation of charge on the tissue - air surface. In magnetic stimulation both of these contributions are significant...
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