Dynamic MRI of Small Electrical Activity

  • Allen W. Song
  • Trong-Kha Truong
  • Marty Woldorff
Part of the METHODS IN MOLECULAR BIOLOGY™ book series (MIMB, volume 489)


Neuroscience methods entailing in vivo measurements of brain activity have greatly contributed to our understanding of brain function for the past decades, from the invasive early studies in animals using single-cell electrical recordings, to the noninvasive techniques in humans of scalp-recorded electroencephalography (EEG) and magnetoencephalography (MEG), positron emission tomography (PET), and, most recently, blood oxygenation level-dependent (BOLD) functional magnetic resonance imaging (fMRI). A central objective of these techniques is to measure neuronal activities with high spatial and temporal resolution. Each of these methods, however, has substantial limitations in this regard. Single-cell recording is invasive and only typically records cellular activity in a single location; EEG/MEG cannot generally provide accurate and unambiguous delineations of neuronal activation spatially; and the most sophisticated BOLD-based fMRI methods are still fundamentally limited by their dependence on the very slow hemodynamic responses upon which they are based. Even the latest neuroimaging methodology (e.g., multimodal EEG/fMRI) does not yet unambiguously provide accurate localization of neuronal activation spatially and temporally. There is hence a need to further develop noninvasive imaging methods that can directly image neuroelectric activity and thus truly achieve a high temporal resolution and spatial specificity in humans. Here, we discuss the theory, implementation, and potential utility of an MRI technique termed Lorentz effect imaging (LEI) that can detect spatially incoherent yet temporally synchronized, minute electrical activities in the neural amplitude range (microamperes) when they occur in a strong magnetic field. Moreover, we demonstrate with our preliminary results in phantoms and in vivo, the feasibility of imaging such activities with a temporal resolution on the order of milliseconds.

Key words

BOLD fMRI neuroimaging noninvasive Lorentz effect 



This work was, in part, supported by the NIH (NS 50329, NS 41328) and NSF (BES 602529).


  1. 1.
    K.K. Kwong, J.W. Belliveau, D.A. Chesler, I.E. Goldberg, R.M. Weisskoff, B.P. Poncelet, D.N. Kennedy, B.E. Hoppel, M.S. Cohen, R. Turner, H.-M. Cheng, T.J. Brady, B.R. Rosen, Dynamic magnetic resonance imaging of human brain activity during primary sensory stimulation, Proc. Natl. Acad. Sci. USA 89 (1992) 5675–5679.CrossRefPubMedGoogle Scholar
  2. 2.
    P.A. Bandettini, E.C. Wong, R.S. Hinks, R.S. Tikofski, J.S. Hyde, Time course EPI of human brain function during task activation, Magn. Reson. Med. 25 (1992)390–397.CrossRefPubMedGoogle Scholar
  3. 3.
    S. Ogawa, D.W. Tank, R. Menon, J.M. Ellermann, S.G. Kim, H. Merkle, K. Ugurbil, Intrinsic signal changes accompanying sensory stimulation: functional brain mapping with magnetic resonance imaging, Proc. Natl. Acad. Sci. USA 89 (1992) 5951–5955.CrossRefPubMedGoogle Scholar
  4. 4.
    S. Ogawa, R.S. Menon, D.W. Tank, D.G. Kim, H. Merkle, J.M. Ellermann, K. Ugurbil, Functional brain mapping by blood oxygenation level-dependent contrast magnetic resonance imaging. A comparison of signal characteristics with a biophysical model, Biophys. J. 64 (1993) 803–812.Google Scholar
  5. 5.
    S.G. Kim, W. Richter, K. Ugurbil, Limitations of temporal resolution in functional MRI, Magn. Reson. Med. 37 (1997) 631–636.CrossRefPubMedGoogle Scholar
  6. 6.
    R.L. Buckner, Event-related fMRI and the hemodynamic response, Hum. Brain Mapp. 6 (1998) 373–377.CrossRefPubMedGoogle Scholar
  7. 7.
    M. Joy, G. Scott, M. Henkelman, In vivo detection of applied electric currents by magnetic resonance imaging, Magn. Reson. Imaging 7 (1989) 89–94.CrossRefPubMedGoogle Scholar
  8. 8.
    J. Bodurka, A. Jesmanowicz, J.S. Hyde, H. Xu, L. Estkowski, S.J. Li, Current-induced magnetic resonance phase imaging, J. Magn. Reson. 137 (1999) 265–271.CrossRefPubMedGoogle Scholar
  9. 9.
    J. Bodurka, P.A. Bandettini, Toward direct mapping of neuronal activity: MRI detection of ultraweak, transient magnetic field changes, Magn. Reson. Med. 47 (2002)1052–1058.CrossRefPubMedGoogle Scholar
  10. 10.
    D. Konn, P. Gowland, R. Bowtell, MRI detection of weak magnetic fields due to an extended current dipole in a conducting sphere: A model for direct detection of neuronal currents in the brain, Magn. Reson. Med. 50 (2003) 40–49.CrossRefPubMedGoogle Scholar
  11. 11.
    H. Kamei, K. Iramina, K. Yoshikawa, S. Ueno, Neuronal current distribution imaging using magnetic resonance, IEEE Trans. Magn. 35 (1999) 4109–4111.CrossRefGoogle Scholar
  12. 12.
    J. Xiong, P.T. Fox, J.H. Gao, Directly mapping magnetic field effects of neuronal activity by magnetic resonance imaging, Hum. Brain Mapp. 20 (2003) 41–49.CrossRefPubMedGoogle Scholar
  13. 13.
    R. Chu, J.A. de Zwart, P. van Gelderen, M. Fukunaga, P. Kellman, T. Holroyd, J.H. Duyn, Hunting for neuronal currents: Absence of rapid MRI signal changes during visual-evoked response, Neuroimage 23 (2004) 1059–1067.Google Scholar
  14. 14.
    M. Bianciardi, F. Di Russo, T. Aprile, B. Maraviglia, G.E. Hagberg, Combination of BOLD-fMRI and VEP recordings for spin-echo MRI detection of primary magnetic effects caused by neuronal currents, Magn. Reson. Imaging 22 (2004)1429–1440.CrossRefPubMedGoogle Scholar
  15. 15.
    D. Konn, S. Leach, P. Gowland, R. Bowtell, Initial attempts at directly detecting alpha wave activity in the brain using MRI, Magn. Reson. Imaging 22 (2004)1413–1427.CrossRefPubMedGoogle Scholar
  16. 16.
    P.A. Bandettini, N. Petridou, J. Bodurka, Direct detection of neuronal activity with MRI: Fantasy, possibility, or reality?, Appl. Magn. Reson. 29 (2005) 65–88.CrossRefGoogle Scholar
  17. 17.
    N. Petridou, D. Pleaz, A.C. Silva, M. Lowe, J. Bodurka, P.A. Bandettini, Direct magnetic resonance detection of neuronal electrical activity, Proc. Natl. Acad. Sci. USA 103 (2006) 16015–16020.CrossRefPubMedGoogle Scholar
  18. 18.
    L.S. Chow, G.G. Cook, E. Whitby, M.N.J. Paley, Investigating direct detection of axon firing in the adult human optic nerve using MRI, Neuroimage 30 (2006) 835–846.CrossRefPubMedGoogle Scholar
  19. 19.
    G.E. Hagberg, M. Bianciardi, B. Maraviglia, Challenges for detection of neuronal currents by MRI, Magn. Reson. Imaging 24 (2006) 483–493.Google Scholar
  20. 20.
    Y. Xue, J.-H. Gao, J. Xiong, Direct MRI detection of neuronal magnetic fields in the brain: Theoretical modeling, Neuroimage 31 (2006) 550–559.CrossRefPubMedGoogle Scholar
  21. 21.
    L.S. Chow, G.G. Cook, E. Whitby, M.N.J. Paley, Investigation of MR signal modulation due to magnetic fields from neuronal currents in the adult human optic nerve and visual cortex, Magn. Reson. Imaging 24 (2006) 681–691.Google Scholar
  22. 22.
    L.M. Parkes, F.P. de Lange, P. Fries, I. Toni, D.G. Norris, Inability to directly detect magnetic field changes associated with neuronal activity, Magn. Reson. Med. 57 (2007) 411–416.Google Scholar
  23. 23.
    A.W. Song, A.M. Takahashi, Lorentz effect imaging, Magn. Reson. Imaging 19 (2001) 763–767.Google Scholar
  24. 24.
    T.-K. Truong, J.L. Wilbur, A.W. Song, Synchronized detection of minute electrical currents with MRI using Lorentz effect imaging, J. Magn. Reson. 179 (2006) 85–91.CrossRefPubMedGoogle Scholar
  25. 25.
    T.-K. Truong, A.W. Song, Finding neuroelectric activity under magnetic-field oscillations (NAMO) with magnetic resonance imaging in vivo, Proc. Natl. Acad. Sci. USA 103 (2006) 12598–12601.CrossRefPubMedGoogle Scholar
  26. 26.
    T.-K. Truong, A. Avram, A. W. Song, Lorentz effect imaging of ionic currents in solutions, J. Magn. Reson. 59 (2008) 221–227.CrossRefGoogle Scholar
  27. 27.
    E.O. Stejskal, J.E. Tanner, Spin diffusion measurements: Spin echoes in the presence of a time-dependent field gradient, J. Chem. Phys. 42 (1965) 288–292.CrossRefGoogle Scholar
  28. 28.
    J. Kimura, Electrodiagnosis in disease of nerve and muscle: Principles and practice, Oxford University Press, Oxford (2001).Google Scholar

Copyright information

© Humana Press, a part of Springer Science+Business Media, LLC 2008

Authors and Affiliations

  • Allen W. Song
    • 1
  • Trong-Kha Truong
    • 1
  • Marty Woldorff
    • 2
  1. 1.Brain Imaging and Analysis Center, Duke UniversityDurham
  2. 2.Center for Cognitive Neuroscience, Duke UniversityDurham

Personalised recommendations