Magnetic Fields of the Brain Resulting from Normal and Pathological Function

  • Harold Weinberg
  • A. W. Robertson
  • D. Crisp
  • B. Johnson


Theoretical physics predicts that currents in biological media result in magnetic fields; however, the predicted fields are so small that they were measurable only recently. One of the first biomagnetic measurements was of fields associated with heart function, measured by Cohen et al. in 1970. Coil magnetometers of the kind they used are usually not sensitive enough for the detection of brain function, which is an order of 10−4 smaller than fields produced by the heart. Consequently it was not until a Josephson junction was incorporated into a superconductive quantum interference device (SQUID) that magnetometers with the required high sensitivity were available for the measurement of brain function. The SQUID is used as ultrasensitive magnetic flux detector. The problem with SQUIDs is that, in order to maintain their superconductivity, the sensor has to be cooled to the temperature of liquid helium (4.2° K). In order to accomplish these low temperatures the SQUID is immersed in liquid helium inside a helium dewar. The rf-SQUID is a superconducting ring with one Josephson junction (weak link) in it. The do-SQUID has two weak links in the ring. Flux transformers transfer flux from a sensing coil to the SQUID. For example, a closed loop of superconducting wire maintains the total magnetic flux inside the loop. If this loop contains two coils, coupled in series, a change of the magnetic flux through one of the coils causes a change in the magnetic flux in the other coil. Thus, magnetic flux is transferred from the sensing coil Ll to the signal coil Ls inside the SQUID (Figure 25.1). In order to increase the signal-to-noise ratio, differential magnetometers, referred to as gradiometers, are utilized in preference to the simple magnetometer (Figure 25.2). The first-order gradiometer has two sensing coils, Ll and L2.


Alpha Activity Contingent Negative Variation Dipole Source Auditory Stimulation Primary Auditory Cortex 
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  1. Anderson, R.A., Snyder, R.L., Merzenich, M.M. (1980): The topographic organization of cortico-collicular projection from physiologically identified loci in the AI, AII, and anterior auditory cortical fields of the cat. J. Comp. Neurol. 191, 479–494CrossRefGoogle Scholar
  2. Angianakis, G., Anninos, P.A. (1988): Localization of epileptiform foci by means of MEG measurements. Int. J. Neurosci. 38, 141–149CrossRefGoogle Scholar
  3. Barth, D.S., Sutherling, W., Engel, J. Jr., Beatty, J. (1982): Neuromagnetic localization of epileptiform spike activity in the human brain. Science 218, 891–894CrossRefGoogle Scholar
  4. Barth, D.S., Sutherling, W., Beatty, J. (1984a): Fast and slow magnetic phenomena in focal epileptic seizures. Science 226, 855–857CrossRefGoogle Scholar
  5. Barth, D.S., Sutherling, W., Engel, J. Jr., Beatty, J. (1984b): Neuromagnetic evidence of spatially distributed sources underlying epileptiform spikes in the human brain. Science 223, 293–296CrossRefGoogle Scholar
  6. Borda, R.P. (1983): The 40/sec middle latency response in Alzheimer’s disease, parkin-son’s disease, and age-matched controls. Unpublished doctoral dissertation, University of TexasGoogle Scholar
  7. Brenner, D. Kaufman, L., Williamson, S.J. (1978): Somatically evoked fields of the human brain. Science 199, 81–83CrossRefGoogle Scholar
  8. Brenner, D., Okada, Y., Maclin E., Williamson, S.J., Kaufman, L. (1981): Evoked magnetic fields reveal different visual areas in the human cortex. In: Biomagnetism. Erne, S.N., Hahlbohm, H.-D., Lubbig, H. (eds.). Berlin: Walter de Gruyter, pp. 431–444Google Scholar
  9. Brickett, P., Robertson, A., Crisp, D., Weinberg, H. (1986): Comparison of the magnetic fields related to alpha activity and visual evoked responses. EPIC V III, Stanford, CaliforniaGoogle Scholar
  10. Carelli, P., Modena, I., Ricci, G.B., Romani, G.L. (1983): Magnetoencephalography. In: Biomagnetism: An interdisciplinary approach. Williamson, S.J., Romani, G.L., Kaufman, L., Modena, I. (eds.). New York: Plenum Press, pp. 469–482Google Scholar
  11. Chapman, R.M., Ilmoniemi, R.J., Barbanera, S., Romani, G. L. (1984): Selective localization of alpha brain activity with neuromagnetic measurements. Electroenceph. Clin. NeurophysioL 58, 569–572CrossRefGoogle Scholar
  12. Cheyne, D.O. (1987): Magnetic and electric field measurements of brain activity preceding voluntary movements: Implications for supplementary motor area function. Doctoral dissertation, Simon Fraser UniversityGoogle Scholar
  13. Cohen, D. (1968): Evidence of magnetic fields produced by alpha-rhythm currents. Science 161, 784–786CrossRefGoogle Scholar
  14. Cohen, D. (1972): Magnetoencephalography: Detection of the brain’s electrical activity with a superconducting magnetometer. Science 175, 664–666CrossRefGoogle Scholar
  15. Cohen, D., Cuffin, B.N. (1985): Search for MEG signals due to auditory brainstem stimulation. In: Biomagnetism: Applications and theory. Weinberg, H., Stroink, G., Katila, T. (eds.). New York: Pergamon Press, pp. 316–320.Google Scholar
  16. Cohen, D. Edelsack, E.A., Zimmerman, J. (1970): Magnetocardiograms taken inside a shielded room with a superconducting point-contact magnetometer. Appl. Phys. Lett. 16, 278–280CrossRefGoogle Scholar
  17. Cohen D., Cuffin, B.N., Kennedy, J.G., Lombroso, C.T., Gumnit, R.J., Schomer, D.L. (1988): Comparison of MEG versus EEG spike localization: Some results in a patient group with focal seizures. Poster presented at the Annual Meeting of the American Epilepsy Society, San FranciscoGoogle Scholar
  18. Cuffin, N.B. (1982): Effects of inhomogeneous regions on electric potentials and magnetic fields: Two special cases. J. Appl. Phys. 53, 9192–9197CrossRefGoogle Scholar
  19. Crisp, D. (1986): Neuromagnetic localization of current dipole sources in complex partial epilepsy. M.A. thesis, Simon Fraser UniversityGoogle Scholar
  20. DeArmond, S., Fusco, M., Dewey, M. (1976): Structure of the human brain, 2nd ed. New York: Oxford PressGoogle Scholar
  21. Deecke, L., Boschert, J., Brickett, P., Weinberg, H. (1985): Magnetoencephalographic evidence for possible supplementary motor area participation in human voluntary movement. In: Biomagnetism: Applications and theory. Weinberg, H., Stroink, G., Katila, T. (eds.). New York: Pergamon Press, pp. 369–372Google Scholar
  22. Deecke, L., Weinberg, H., Brickett, P. (1982): Magnetic fields of the human brain accompanying voluntary movement: Bereitschaftsmagnetfeld. Exp. Brain Res. 48, 144–148Google Scholar
  23. Fiumara, R., Campitelli, F., Romani, G.L., Leoni, R. Caporali, M., Zanasi, M., Cappiello, A., Fioriti, G., Modena, I. (1985): Neuromagnetic study of endogenous fields related to the contingent negative variation. In: Biomagnetism: Applications and theory. Weinberg, H., Stroink, G., Katila, T. (eds.). New York: Pergamon Press, pp. 336–342Google Scholar
  24. Galambos, R., Makeig, S., Talmachoff, P.J. (1981): A 40-Hz auditory potential recorded from the human scalp. Proc. Nat. Acad. Sci. 78, 2643–2647CrossRefGoogle Scholar
  25. Geselowitz, D.B. (1967): On bioelectric potentials in an inhomogeneous volume conductor. J. Biophys. 7, 1–11CrossRefGoogle Scholar
  26. Hari, R. (1985): Somatically evoked magnetic fields. Med. BioL Eng. Comput. 22 (Supp. 1), 29–31Google Scholar
  27. Hari, R. Aittoniemi, K., Jarvinen, M.L., Katila, T., Varpula, T. (1980): Auditory evoked transient and sustained magnetic fields of the human brain. Localization of neural generators. Exp. Brain Res. 40, 237–240CrossRefGoogle Scholar
  28. Hari, R. Antervo, A., Katila, T., Poutanen, T., Seppanen, M., Tuomisto, T., Varpula, T. (1983): Cerebral magnetic fields associated with voluntary limb movements in man. Il Nuovo Cimento 2D 1, 484–495CrossRefGoogle Scholar
  29. Hari, R. Hamalainen, M., Ilmoniemi, R. Kaukoranta, E., Reinikainen, K., Salminen, J., Alho, K., Naatanen, R., Sams, M. (1984a): Responses of the primary auditory cortex to pitch changes in a sequence of tone pips: Neuromagnetic recordings in man. Neurosci. Lett. 50, 127–132CrossRefGoogle Scholar
  30. Hari, R., Reinkainen, K. Kaukoranta, E., Hamalainen, M., Ilmoniemi, R., Penttinen, A., Salminen, J., Teszner, D. (1984b): Somatosensory evoked cerebral magnetic fields from SI and SII in man. Electroenceph. Clin. Neurophysiol. 57, 254–263CrossRefGoogle Scholar
  31. Harrop, R., Weinberg, H., Brickett, P., Dykstra, C., Robertson, A., Cheyne, D., Baff, M., Crisp, D. (1986): An inverse solution method for the simultaneous localization of two dipoles. Presented at the meeting of the Institute of Physics: Magnetism Subcommittee, Milton Keynes, EnglandGoogle Scholar
  32. Harrop, R., Weinberg, H., Brickett, P., Dykstra, C., Robertson, A., Cheyne, D.O., Baff, M., Crisp, D. (1987): The biomagnetic inverse problem: Some theoretical and practical considerations. Phys. Med. Biol. 32, 1545–1557CrossRefGoogle Scholar
  33. Imig, T.J., Morel, A. (1983): Organization of the thalamocortical auditory system in the cat. Annu. Rev. Neurosci. 6, 95–120CrossRefGoogle Scholar
  34. Kaufman, L., Okada, Y., Brenner, D., Williamson, S.J. (1981): On the relation between somatic evoked potentials and fields. Int. J. Neurosci. 15, 223–239CrossRefGoogle Scholar
  35. Knight, R.T. (1986): Neurophysiological mechanisms: Evidence from human lesion data. Presented at the Eighth International Conference on Event-Related Potentials of the Brain, CaliforniaGoogle Scholar
  36. Kornhuber, H.H., Deecke, L. (1965): Hirnpotenthalanderungen bei Willkürbewegungen and passiven Bewegungen des Menschen: Bereitschaftspotential and reafferente Potentiale. Pflugers Arch. 284, 1–17CrossRefGoogle Scholar
  37. Lounasmaa, O.V., Williamson, Si., Kaufman, L., Tanenbaum, R. (1985): Visually evoked responses from non-occipital areas of the human cortex. In: Biomagnetism: Applications and theory. Weinberg, H., Stroink, G., Katila, T. (eds.). New York: Pergamon Press, pp. 348–353Google Scholar
  38. Modena, I., Ricci, G.B., Barbanera, S., Leoni, R., Carelli, P. (1982): Biomagnetic measurements of spontaneous brain activity in epileptic patients. Electroenceph. Clin. NeurophysioL 54, 622–628CrossRefGoogle Scholar
  39. Nunez, P.L. (1988): Methods to estimate spatial properties of dynamic cortical source activity. In: Functional brain imaging. Pfurtscheller, G., Lopes da Silva, F.H. (eds.). Toronto: Hans Huber Publishers, pp. 3–10Google Scholar
  40. Okada, Y.C. (1985): Discrimination of localized and distributed current dipole sources and localized single and multiple sources. In: Biomagnetism: Applications and theory. Weinberg, H., Stroink, G., Katila, T. (eds.). New York: Pergamon Press, pp. 266–272Google Scholar
  41. Okada, Y.C., Kaufman, L., Brenner, D., Williamson, S.J. (1981): Application of a SQUID to measurement of somatically evoked fields: Transient responses to electrical stimulation of the median nerve. In: Biomagnetism. Erne, S.N., Hahlmohm, H.-D., Lubbig, H. (eds.). Berlin: Walter de Gruyter, pp. 445–461Google Scholar
  42. Okada, Y., Kaufman, L., Brenner, D., Williamson, S.J. (1982a): Modulation transfer functions of the human visual system revealed by magnetic field measurements. Vision Res. 22, 319–333CrossRefGoogle Scholar
  43. Okada, Y., Williamson, Si., Kaufman, L. (1982b): Magnetic field of the human sensori-motor cortex. Int. J. Neurosci. 17, 33–38CrossRefGoogle Scholar
  44. Okada, Y.C., Kaufman, L., Williamson, S.J. (1983): The hippocampal formation as a source of the slow endogenous potentials. Electroenceph. Clin. Neurophysiol. 55, 417426Google Scholar
  45. Reite, M., Zimmerman, J.T., Edrich, J., Zimmerman, J.E. (1976): The human magnetoencephalograph: Some EEG and related correlations. Electroenceph. Clin. Neurophysiol. 40, 59–66CrossRefGoogle Scholar
  46. Reite, M., Edrich, J., Zimmerman, J.T., Zimmerman, J.E. (1978): Human magnetic auditory evoked fields. Electroenceph. Clin. Neurophysiol. 45, 114–117, 20Google Scholar
  47. Ricci, G.B. (1983): Clinical magnetoencephalography. Il Nuovo Cimento 2, 517–537CrossRefGoogle Scholar
  48. Ricci, G.B., Buonomo, S., Peresson, M., Romani, G.L., Salustri, C., Modena, I. (1985): Multichannel neuromagnetic investigation of focal epilepsy. Med. Biol. Comput. 23 (suppl. 1), 42–44Google Scholar
  49. Romani, G.L. Williamson, S.J. (eds.) (1983): Proceedings of the Fourth International Workshop on Biomagnetism. Il Nuovo Cimento, 2D 2, 123–664Google Scholar
  50. Romani, G.L., Leoni, R. (1985): Localization of cerebral courses by neuromagnetic measurements. In: Biomagnetism: Applications and theory. Weinberg, H., Stroink, G., Katila, T. (eds.). New York: Pergamon Press, pp. 205–220Google Scholar
  51. Romani, G.L., Williamson, Si., Kaufman, L. (1982a): Tonotopic organization of the human auditory cortex. Science 216, 1339–1340CrossRefGoogle Scholar
  52. Romani, G.L., Williamson, S.J., Kaufman, L., Brenner, D. (1982b): Characterization of the human auditory cortex by the neuromagnetic method. Exp. Brain Res. 47, 381–393CrossRefGoogle Scholar
  53. Ryugo, D.K., Weinberger, N.M. (1976): Corticofugal modulation of the medial geniculate body. Exp. Neurol. 51, 377–391CrossRefGoogle Scholar
  54. Spydell, J.R., Pattee, G., Goldie, W.D. (1985): The 40 Hz auditory event-related potential: Normal values and effects of lesions. Electroenceph. Clin. Neurophysiol 62, 193–202CrossRefGoogle Scholar
  55. Vieth, J. Schueler, P., Harsdorf, S.V., Fischer, H., Grimm, U. (1988): AC-MEG and AC-EEG at verified focal lesions and DC-MEG shifts during seizure and interictal periods. Presented at the Annual Meeting of the American Epilepsy Society, San Francisco.Google Scholar
  56. Vrba, J., Fife, M., Burbank, M., Weinberg, H., Brickett, P. (1982): Spatial discrimination in SQUID gradiometers and 3rd order gradiometer performance. Can. J. Phys. 60, 1060–1073CrossRefGoogle Scholar
  57. Vvedensky, V.L., Ilmoniemi, R.J., Kajola, M.J. (1985): Study of the alpha rhythm with a 4 channel SQUID magnetometer. Merl Biol. Eng. Comput. 23 ( Suppl. Part 1 ), 11–12Google Scholar
  58. Walter, W.G. (1953): The living brain. London: DuckworthGoogle Scholar
  59. Weinberg, H., Brickett, P.A., Deecke, L., Boschert, J. (1983): Slow magnetic fields preceding movement and speech. Il Nuovo Cimento, 2D 1, 495–504CrossRefGoogle Scholar
  60. Weinberg, H., Brickett, P.A., Vrba, J., Fife, A.A., Burbank, M.B. (1984): The use of a SQUID third order spatial gradiometer to measure magnetic fields of the brain. NYAcad. Sci. 42, 743–752CrossRefGoogle Scholar
  61. Weinberg, H., Brickett, P., Neill, R.A., Fenelon, B., Baff, M. (1985a): Magnetic fields evoked by random-dot stereograms. In: Biomagnetism: Applications and theory. Weinberg, H., Stroink, G., Katila, T. (eds.). New York: Pergamon Press, pp. 354–359Google Scholar
  62. Weinberg, H., Stroink, G., Katila, T. (eds.). (1985b): Biomagnetism: Applications and theory. New York: Pergamon Press.Google Scholar
  63. Weinberg, H., Brickett, P., Coolsma, F., Baff, M. (1986): Magnetic localization of intracranial dipoles: Simulation with a physical model. Electroenceph. Clin. Neurophysiol. 64, 159–170CrossRefGoogle Scholar
  64. Weinberg, H., Brickett, P., Robertson, A., Crisp, D., Cheyne, D., Harrop, R. (1987a): A study of sources in the human brain associated with stereopsis. Presented at the Advanced Group for Aerospace Research and Development (NATO) Conference, Trondheim, NorwayGoogle Scholar
  65. Weinberg, H., Brickett, P., Robertson, A., Harrop, R., Cheyne, D.O., Crisp, D., Baff, M., Dykstra, C. (1987b): The magnetoencephalographic localization of source-systems in the brain: Early and late components of event related potentials. J. Alcohol. 4, 339–345CrossRefGoogle Scholar
  66. Weinberg, H., Cheyne, D., Brickett, P., Gordon, R., Harrop, R. (1987c): The interaction of thalamo-cortical systems in the 40 Hz following response. Presented at the Advanced Group for Aerospace Research and Development (NATO) Conference, Trondheim, NorwayGoogle Scholar
  67. Weinberg, H., Crisp, D., Brickett, P., Hanop, R., Purves, S.J., Li, D.K.B., Jones, M.W., Baff, M. (1987d) The combination of MEG and MRI in the estimation of sources associated with interictal discharges. In: Functional localization: A challenge for bio-magnetism. Erne, S.N., Romani, G.L. (eds.). Singapore: World ScientificGoogle Scholar
  68. Weinberg, H., Robertson, A., Brickett, P., Cheyne, D., Harrop, R., Dykstra, C., Baff, M. (1987c): Functional localization of current sources in the human brain associated with the discrimination of moving visual stimuli. In: Current trends in event-related potential research. Johnson, R.Jr., Parasuraman, R., Rohrbaugh, J.W. (eds.). New York: Pergamon PressGoogle Scholar
  69. Weinberg, H., Cheyne, D.O., Brickett, P., Harrop, R., Gordon, R. (1988): An interaction of cortical sources associated with simultaneous auditory and somesthetic stimulation. In; Functional brain imaging. Pfurtscheller, G., Lopes da Silva, F.H. (eds.). Toronto: Hans Huber Publishers, pp. 83–88Google Scholar
  70. Weinberg, H., Stroink, G., Katila, T. (1988). Biomagnetism. In: Encyclopedia of Medical Devices and Instrumentation, vol 3. Webster J. C. (ed.). New York: John Wiley and SonsGoogle Scholar
  71. Williamson, S.J., Romani, G.L., Kaufman, L., Modena, I. (eds.) (1983): Biomagnetism: An interdisciplinary approach. New York: Plenum PressGoogle Scholar

Copyright information

© Springer Science+Business Media New York 1990

Authors and Affiliations

  • Harold Weinberg
  • A. W. Robertson
  • D. Crisp
  • B. Johnson

There are no affiliations available

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