Book contents
- Frontmatter
- Dedication
- Contents
- Preface
- Reserved Physical Symbols and Quantities
- Abbreviations
- 1 Introduction
- 2 Charges, Currents, Fields, and Potentials in the Brain
- 3 Neural Dynamics
- 4 Volume-Conductor Theory
- 5 Conductivity of Brain Tissue
- 6 Schemes for Computing Extracellular Potentials
- 7 Spikes
- 8 Local Field Potentials (LFPs)
- 9 Electroencephalography (EEG)
- 10 Electrocorticography (ECoG)
- 11 Magnetoencephalography (MEG)
- 12 Diffusion Potentials in Brain Tissue
- 13 Final Comments and Outlook
- Appendix A Frequency-Dependent Length Constant
- Appendix B Derivation of the Current-Dipole Approximation
- Appendix C Electric Stimulation
- Appendix D Derivation of the Point-Source Equation for Anisotropic Medium
- Appendix E Statistical Measures
- Appendix F Fourier-Based Analyses
- Appendix G Derivation of Formulas for Population Signals
- Appendix H Equations for Computing Magnetic Fields
- Appendix I Derivation of the MC+ED Scheme
- References
- Index
11 - Magnetoencephalography (MEG)
Published online by Cambridge University Press: 30 May 2024
Book contents
- Frontmatter
- Dedication
- Contents
- Preface
- Reserved Physical Symbols and Quantities
- Abbreviations
- 1 Introduction
- 2 Charges, Currents, Fields, and Potentials in the Brain
- 3 Neural Dynamics
- 4 Volume-Conductor Theory
- 5 Conductivity of Brain Tissue
- 6 Schemes for Computing Extracellular Potentials
- 7 Spikes
- 8 Local Field Potentials (LFPs)
- 9 Electroencephalography (EEG)
- 10 Electrocorticography (ECoG)
- 11 Magnetoencephalography (MEG)
- 12 Diffusion Potentials in Brain Tissue
- 13 Final Comments and Outlook
- Appendix A Frequency-Dependent Length Constant
- Appendix B Derivation of the Current-Dipole Approximation
- Appendix C Electric Stimulation
- Appendix D Derivation of the Point-Source Equation for Anisotropic Medium
- Appendix E Statistical Measures
- Appendix F Fourier-Based Analyses
- Appendix G Derivation of Formulas for Population Signals
- Appendix H Equations for Computing Magnetic Fields
- Appendix I Derivation of the MC+ED Scheme
- References
- Index
Summary
The magnetoencephalographic signal is the magnetic field recorded outside the scalp of the head. It is believed to originate from the combined activity of large populations of neurons. In forward models of MEG signals, the neural output is typically represented in terms of equivalent current dipoles. We here go through the mathematical equations for computing MEG signals from current dipoles, present computer simulations of MEG signals using simplified models of the head geometry, and show how the predicted MEG signals depend on the chosen head model and orientations of the dipoles. We also present a formalism for modeling the magnetic field inside brain tissue.
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- Electric Brain SignalsFoundations and Applications of Biophysical Modeling, pp. 276 - 288Publisher: Cambridge University PressPrint publication year: 2024