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Magnetoencephalography: A tool for functional brain imaging

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Summary

At present, one of the most promising windows to the functional organization of the human brain is magnetoencephalography (MEG). By mapping the magnetic field distribution outside the head the sites of neural events can be located with an accuracy of a few millimeters and the temporal evolution of the activation can be traced with a millisecond resolution. This paper reviews some forward field calculation approaches suitable for the interpretation of the brain's electromagnetic signals. Inverse modelling with multiple dipoles is described in detail. An example of the analysis of the somatosensory evoked-responses illustrates the potential of multiple signal classification (MUSIC) algorithm in finding optimal dipole positions.

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References

  • Ahonen, A.I., Hämäläinen, M.S., Kajola, M.J., Knuutila, J.E.T., Lounasmaa, O.V., Simola, J.T., Tesche, C.D., and Vilkman, V.A. Multichannel SQUID systems for brain research. IEEE Trans. Magn., MAG, 1991, 27: 2786–2792.

    Google Scholar 

  • Arthur, R.M. and Geselowitz, D.B. Effect of inhomogeneities on the apparent location and magnitude of a cardiac current dipole source. IEEE Trans. Biomed. Eng., BME, 1970, 17: 141–146.

    Google Scholar 

  • Cuffin, B.N. and Cohen, D. Magnetic fields of a dipole in special volume conductor shapes. IEEE Trans. Biomed. Eng., BME, 1977, 24: 372–381.

    Google Scholar 

  • Geselowitz, D.B. On bioelectric potentials in an inhomogeneous volume conductor. Biophys. J., 1967, 7: 1–11.

    Google Scholar 

  • Golub, G.H. and van Loan, C.F. Matrix Computations. The Johns Hopkins University Press, Baltimore, second edition, 1989.

    Google Scholar 

  • Hari, R., Reinikainen, K., Kaukoranta, E., Hämäläinen, M., Ilmoniemi, R., Penttinen, A., Salminen, J. and Teszner, D. Somatosensory evoked cerebral magnetic fields from SI and SII in man. Electroenceph. Clin. Neurophysiol., 1984, 57: 254–263.

    PubMed  Google Scholar 

  • Hari, R. The neuromagnetic method in the study of the human auditory cortex. In F.Grandoli, M.Hoke, and G.L. Romani, editors, Auditory Evoked Magnetic Fields and Electric Potentials, Karger, Basel, 1990, 222–282.

    Google Scholar 

  • Hari, R. On brain's magnetic responses to sensory stimuli. J. Clin. Neurophysiol., 1991, 8: 157–169.

    PubMed  Google Scholar 

  • Hari, R., Karhu, J., Hämäläinen, M., Knuutila, J., Sams, J., and Vilkman, V. Functional organization of the human first and second somatosensory cortex as revealed by neuromagnetic measurements. European J. Neurosci., 1992 (in press).

  • Hämäläinen, M.S., Hari, R., Ilmoniemi, R., Knuutila, J., and Lounasmaa, O.V. Magnetoencephalography - theory, instrumentation, and applications to noninvasive studies of the working human brain. Rev. Mod. Phys., 1993, (in press).

  • Hämäläinen M.S. and Ilmoniemi, R.J. Interpreting measured magnetic fields of the brain: Estimates of current distributions. Technical Report TKK-F-A559, Helsinki University of Technology, 1984.

  • Hämäläinen, M.S. and Sarvas, J. Realistic conductivity geometry model of the human head for interpretation of neuromagnetic data. IEEE Trans. Biomed. Eng., 1989, 36: 165–171.

    PubMed  Google Scholar 

  • Helmholtz, H. Ueber einige Gesetze der Vertheilung elektrischer Ströme in körperlichen Leitern, mit Anwendung auf die thierisch-elektrischen Versuche. Ann. Phys. Chem., 1853, 89: 211–233, 353–377.

    Google Scholar 

  • Hoenig, H.E., Daalmans, G.M., Bär, L, Bömmel, F., Paulus, A., Uhl, D., Weisse, H.J., Schneider, S., Seifert, H., Reichenberger, H., and Abraham-Fuchs, K. Multi channel dc SQUID sensor array for biomagnetic applications. IEEE Trans. Magn., MAG, 1991, 27: 2777–2785.

    Google Scholar 

  • Ilmoniemi, R.J., Hämäläinen, M.S. and Knuutila, J. The forward and inverse problems in the spherical model. In H. Weinberg, G. Stroink, and T. Katila, editors, Biomagnetism: Applications & Theory, Pergamon Press, New York, 1985, 278–282.

    Google Scholar 

  • Kajola, M., Ahlfors, S., Ehnholm, G.J., Hällström, J., Hämäläinen, M.S., Ilmoniemi, R.J., Kiviranta, M., Knuutila, J., Lounasmaa, O.V., Tesche, C.D., and Vilkman, V. A 24-channel magnetometer for brain research. In S.J. Williamson, M. Hoke, G. Stroink, and M. Kotani, editors, Advances in Biomagnetism, New York, Plenum, 1989, 673–676.

    Google Scholar 

  • Kaukoranta, E., Hari, R., Hämäläinen, M., and Huttunen, J. Cerebral magnetic fields evoked by peroneal nerve stimulation. Somatosensory Res., 1986, 3: 309–321.

    Google Scholar 

  • Kullmann, W.H., Jandt, K.D., Rehm, K., Schlitt, H.A., Dallas, W.J., and Smith, W.E. A linear estimation approach to biomagnetic imaging. In S.J. Williamson, M. Hoke, G. Stroink, and M. Kotani, editors, Advances in Biomagnetism, New York, Plenum, 1989, 571–574.

    Google Scholar 

  • Meijs, J.W.H., and Peters, M.J. The EEG and MEG, using a model of eccentric spheres to describe the head. IEEE Trans. Biomed. Eng., BME, 1987, 34: 913–920.

    Google Scholar 

  • Mosher, J.C., Lewis, P.S., and Leahy R. Multiple dipole modeling and localization from spatio-temporal MEG data. IEEE Trans. Biomed. Eng., 1992, BME-39: 541–557.

    Google Scholar 

  • Mosher, J.C., Lewis, P.S., Leahy, R. and Singh, M. Multiple dipole modeling of spatio-temporal MEG data. In A.F. Gmitro, P.S. Idell, and I.J. LaHaie, editors, Digital Image Synthesis and Inverse Optics, Proc. SPIE 1351, 1990, 364–375.

  • de Munck, J.C. The potential distribution in a layered spheroidal volume conductor. J. Appl. Phys., 1988, 64: 464–470.

    Google Scholar 

  • de Munck, J.C. A mathematical and physical interpretation of the electromagnetic field of the brain. PhD thesis, University of Amsterdam, 1989.

  • de Munck, J.C. The estimation of time-varying dipoles on the basis of evoked potentials. Electroenceph. Clin. Neurophysiol., 1990, 77: 156–160.

    PubMed  Google Scholar 

  • de Munck, J.C. A linear discretization of the volume conductor boundary integral equation using analytically integrated elements. IEEE Trans. Biomed. Eng., in press 1992.

  • Oostendorp, T.F. and van Oosterom, A. Source parameter estimation in inhomogeneous volume conductors of arbitrary shape. IEEE Trans. Biomed. Eng., BME, 1989, 36: 382–391.

    Google Scholar 

  • Ribary, U., Ioannides, A.A., Singh, K.D., Hasson, R., Bolton, J.P.R., Lado, F., Mogilner, A., and Llin'as, R. Magnetic field tomography of coherent thalamo-cortical 40-Hz oscillations in humans. Proc. Natl. Acad. Sci. USA, 1991, 88: 11037–11041.

    PubMed  Google Scholar 

  • Romani, G.L., and Rossini, P. Neuromagnetic functional localization: Principles, state of the art, and perspectives. Brain Topography, 1988, 1: 5–19.

    PubMed  Google Scholar 

  • Ryhänen, T., Seppä, H., Ilmoniemi, R., and Knuutila, J. SQUID magnetometers for low-frequency applications. J. Low Temp. Phys., 1989, 76: 287–386.

    Google Scholar 

  • Sarvas, J. Basic mathematical and electromagnetic concepts of the biomagnetic inverse problem. Phys. Med. Biol., 1987, 32: 11–22.

    PubMed  Google Scholar 

  • Scherg, M., Hari, R., and Hämäläinen, M. Frequency-specific sources of the auditory N19-P30-P50 response detected by a multiple source analysis of evoked magnetic fields and potentials. In S.J. Williamson, M. Hoke, G. Stroink, and M. Kotani, editors, Advances in Biomagnetism, New York, Plenum, 1989, 97–100.

    Google Scholar 

  • Scherg, M. Fundamentals of dipole source potential analysis. Karger, Basel, 1990, 40–69.

    Google Scholar 

  • Schmidt, R.O. Multiple emitter location and signal parameter estimation. IEEE Trans. Antennas Propagat., AP, 1986, 34: 276–280.

    Google Scholar 

  • Urankar, L. Common compact analytical formulas for computation of geometry integrals on a basic Cartesian subdomain in boundary and volume integral methods. Eng. Anal. Boundary Elements, 1990, 7: 124–129.

    Google Scholar 

  • Wax, M., and Kailath, T. Detection of signals by information theoretic criteria. IEEE Trans. Acoust., Speech and Signal Processing, ASSP, 1985, 33: 387–392.

    Google Scholar 

  • Williamson, S.J., and Kaufman, L. Biomagnetism. J. Magn. Magn. Mat., 1981, 22: 129–201.

    Google Scholar 

  • Williamson, S.J., Lü, Z.-L., Karron, D. and Kaufman, L. Advantages and limitations of magnetic source imaging. Brain Topography, 1991, 4: 169–180.

    PubMed  Google Scholar 

  • Yin, Y.Q. and Krishnaiah, P.R. On some nonparametric methods for detection of the number of signals. IEEE Trans. Acoust., Speech and Signal Processing, ASSP, 1987, 35: 1533–1538.

    Google Scholar 

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Authors and Affiliations

  1. Low Temperature Laboratory, Helsinki University of Technology, 02150, Espoo, Finland

    Matti S. Hämäläinen

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  1. Matti S. Hämäläinen
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I thank Prof. Riitta Hari, Prof. Olli V. Lounasmaa, and Dr. Juha Simola for valuable comments on this manuscript. This work was supported by Finnish National Fund for Research and Development (SITRA) and Instrumentarium Corp.

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Hämäläinen, M.S. Magnetoencephalography: A tool for functional brain imaging. Brain Topogr 5, 95–102 (1992). https://doi.org/10.1007/BF01129036

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