Abstract
We determined the location of excitation for different positions of a round and butterfly coil duringin vitro magnetic stimulation of cut peripheral nerves. We analyzed the conditions under which excitation occurs, either at the termination or at the peak of the field gradients (first spatial derivative of the electric field). These results were then compared to predictions about the location of excitation sites from a theoretical model of magnetic stimulation of finite neuronal structures. Excitation along a straight nerve occurred at terminations when 1) a coil was positioned close to the end of a nerve (at least one diameter length from the end), 2) a nerve ended in a finite terminating impedance much greater than the axial resistance of the nerve, 3) the induced electric field was of sufficient magnitude, pointing in a direction away from the axis of a nerve. Excitation occurred at the negative peak of the field gradients along a nerve when 1) a coil was positioned far away from the ends of a nerve, 2) there were no geometric or volume conductor inhomogeneities around a nerve, and 3) it was of sufficient magnitude. Threshold strengths for excitation at terminations were significantly lower than that for field gradient excitation and comparable to that due to geometric and volume conductor inhomogeneities.
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Amassian, V. E., L. Eberle, P. J. Maccabee, and R. Q. Cracco. Modelling magnetic coil excitation of human cerebral cortex with a peripheral nerve immersed in a brain-shaped volume conductor: the significance of fiber bending in excitation.Electroencephalogr. Clin. Neurophysiol. 85:291–301, 1992.
Amassian, V. E., P. J. Maccabee, R. Q. Cracco, J. B. Cracco, M. Somasundaram, J. C. Rothwell, L. Eberle, K. Henry, and A. P. Rudell. The polarity of the induced electric field influences magnetic coil inhibition of human visual cortex: implications for the site of excitation.Electroencephalogr. Clin. Neurophysiol. 93:21–26, 1994.
Basser, P. J., and B. J. Roth. Stimulation of a myelinated nerve axon by electromagnetic induction.Med. Biol. Eng. Comput. 29:261–268, 1991.
Britton, T. C., B. Meyer, J. Herdmann, and R. Benecke. Clinical use of the magnetic stimulator in the investigation of peripheral conduction time.Muscle Nerve 13:396–406, 1990.
Cohen, D., and B. N. Cuffin. Developing a more focal magnetic stimulator. Part I: Some basic principles.J. Clin. Neurophysiol. 8:102–111, 1991.
Cros, D., T. J. Day, and B. T. Shanani, Spatial dispersion of magnetic stimulation in peripheral nerves.Muscle Nerve 13: 1076–1082, 1990.
Davey, K., C. H. Cheng, and C. M. Epstein. Prediction of magnetically induced electric fields in biological tissue.IEEE Trans. Biomed. Eng. 38:418–422, 1991.
Durand, D., A. S. Ferguson, and T. Dalbasti. Effects of surface boundary on neuronal magnetic stimulation.IEEE Trans. Biomed. Eng. 37:588–597, 1992.
Eaton, H. The electric field induced in a spherical volume conductor from arbitrary coils: application to magnetic stimulation and MEG.Med. Biol. Eng. Comput. 30:433–440, 1992.
Emery, D. G., J. H. Lucas, and G. W. Gross. The sequence of ultrastructural changes in cultured neurons after dendritic transection.Exp. Brain Res. 67:41–51, 1987.
Epstein, C. M., D. G. Schwartzberg, K. R. Davey, and D. B. Sudderth. Localizing the site of magnetic brain stimulation in humans.Neurology 40:666–670, 1990.
Esselle, K. P., and M. A. Stuchly. Quasi-static electric field in a cylindrical volume conductor induced by external coils.IEEE Trans. Biomed. Eng. 41:151–158, 1994.
Estrem, S. A., T. McCormack, S. S. Haghighi, and T. Potter. A comparison of magnetic and electrical stimulation of facial nerve at the cerebello-pontine angle in the dog.Electroencephalogr. Clin. Neurophysiol. 75:558–560, 1990.
Grandori, F., and P. Ravazzani. Magnetic stimulation of the motor cortex—theoretical considerations.IEEE Trans. BME 38:180–191, 1991.
Krause, T. L., H. M. Fishman, M. L. Ballinger, and G. D. Bittner. Extent and mechanism of sealing in transected giant axon of squid and earthworms.J. Neurosci. 14:6638–6651, 1994.
Krause, T. L., Y. Magarshank, H. M. Fishman, and G. D. Bittner. Membrane potential and input resistance are ambiguous measures of sealing of transected cable-like structures.Biophys. J. 68:795–799, 1995.
Liang, D. H., G. T. A. Kovacs, C. W. Storment, and R. L. White. A method for evaluating the selectivity of electrodes implanted for nerve stimulation.IEEE Trans. Biomed. Eng. 38:443–449, 1991.
Maccabee, P. J., V. E. Amassian, L. Eberle, A. Rudell, R. Q. Cracco, K. S. Lai, and M. Somasundaram. Measurement of the electric field induced into inhomogenous volume conductors by magnetic coils: applications to human spinal geometry.Electroencephalogr. Clin. Neurophysiol. 81:224–237, 1991.
Maccabee, P. J., V. E. Amassian, L. Eberle, A. P. Rudell, and R. Q. Cracco. The magnetic coil activates amphibian and primate nerve in-vitro at two sites and selectively at a bend.J. Physiol. (Lond.) 446:208P, 1992.
Maccabee, P. J., V. E. Amassian, L. P. Eberle, and R. Q. Cracco. Magnetic coil stimulation of straight and bent amphibian and mammalian peripheral nerve in vitro: locus of excitation.J. Physiol. (Lond.) 460:201–219, 1993.
McRobbie, D. Design and instrumentation of a magnetic nerve stimulator.J. Phys. E. Sci. Instrum. 18:74–78, 1985.
Murray, N. M. F. The clinical usefulness of magnetic cortical stimulation.Electroencephalogr. Clin. Neurophysiol. 85:81–85, 1992.
Nagarajan, S. S., and D. Durand. Determination of excitation sites during magnetic stimulation of nerve fibers. 14th Annual International Conference of the IEEE-EMBS, Vol. 4, 1992, pp. 1426–1427.
Nagarajan, S. S., D. Durand, and E. N. Warman. Effects of induced electric fields on finite neuronal structures: a stimulation study.IEEE Trans. Biomed. Eng. 40:1175–1188, 1993.
Nagarajan, S. S., and D. M. Durand. 1995. Analysis of magnetic stimulation of a concentric axon in a nerve bundle.IEEE Trans. Biomed. Eng. 42:926–933.
Nagarajan, S. S., D. M. Durand, B. J. Roth, and R. S. Wijesinghe. Magnetic stimulation of axons in a nerve bundle: effects of current distribution in the nerve bundle.Ann. Biomed. Eng. 23:116–126, 1995.
Naples, G. G., J. T. Mortimer, A. Scheiner, and J. Sweeney, A spiral nerve cuff electrode for peripheral nerve stimulation.IEEE Trans. Biomed. Eng. 35:905–916, 1988.
Nilsson, J., M. Panizza, B. J. Roth, P. J. Basser, L. G. Cohen, G. Caruso, and M. Hallett. Determining the site of stimulation during magnetic stimulation of a peripheral nerve.Electroencephalogr. Clin. Neurophysiol. 85:253–264, 1992.
Pascual-Leone, A., D. Nguyet, L. G. Cohen, J. P. Brasil-Neto, A. Camerota, and M. Hallett. Modulation of muscle responses evoked by transcranial magnetic stimulation during the acquisition of new fine motor skills.J. Neurophysiol. 74:1037–1045, 1995.
Plonsey, R., and R. C. Barr. Electric field stimulation of excitable tissue.IEEE Trans. Biomed. Eng. 42:329–336, 1995.
Ranck, J. B. J. Which elements are excited in electrical stimulation of mammalian central nervous system: a review.Brain Res. 98:417, 1975.
Rattay, F. Analysis of models for extracellular fiber stimulation.IEEE Trans. Biomed. Eng. 36:676–682, 1989.
Ravnborg, M., M. Blinkenberg, and K. Dahl. Significance of magnetic coil position in peripheral motor nerve stimulation.Muscle Nerve 13:681–686, 1990.
Reilly, J. P. Peripheral nerve stimulation by induced electric currents: exposure to time-varying magnetic fields.Med. Biol. Eng. Comput. 27:101–110, 1989.
Roth, B. J., and P. J. Basser. A model for stimulation of a nerve fiber by electromagnetic induction.IEEE Trans. Biomed. Eng. 37:588–597, 1990.
Roth, B. J., L. G. Cohen, and M. Hallett. The electric field induced during magnetic stimulation.Electroencephalogr. Clin. Neurophysiol. Suppl. 43:268–278, 1991.
Roth, B. J., L. G. Cohen, M. Hallett, W. Friauf, and P. J. Basser. A theoretical calculation of the electric field induced by magnetic stimulation of a peripheral nerve.Muscle Nerve 13:734–741, 1990.
Roth, B. J., P. J. Maccabee, L. P. Eberle, V. E. Amassian, M. Hallett, J. Cadwell, G. D. Anselmi, and G. T. Tatarian. In vitro evaluation of a 4-leaf coil design for magnetic stimulation of peripheral nerve.Electroencephalogr. Clin. Neurophysiol. 93:68–74, 1994.
Spira, M. E., D. Benbassat, and A. Dormann. Resealing of the proximal and distal cut ends of transected axons: electrophysiological and ultrastructural analysis.J. Neurobiol. 24:300–316, 1993.
Tofts, P. S., and N. M. Branston. The measurement of electric field, and the influence of surface charge, in magnetic stimulation.Electroencephalogr. Clin. Neurophysiol. 81:238–239, 1991.
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Nagarajan, S.S., Durand, D.M. & Hsuing-Hsu, K. Mapping location of excitation during magnetic stimulation: Effects of coil position. Ann Biomed Eng 25, 112–125 (1997). https://doi.org/10.1007/BF02738543
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DOI: https://doi.org/10.1007/BF02738543