Effects of neuronal magnetic fields on MRI: Numerical analysis with axon and dendrite models

Whether the neuronal magnetic fields (NMFs) could cause measurable MRI signal changes in the human brain seems to be still controversial. In this study, we have numerically investigated the NMF effects on the MRI signal using two separate current source models for axons and dendrites. Since intracellular current distributions are different in axons and dendrites, the NMFs emanating from axons and dendrites are also very different from each other. Due to the quadripole configuration of the intracellular current flowing through an axon, the axonal magnetic field is bipolar causing virtually no changes in the MRI signal. On the contrary, the dendritic magnetic field is unipolar so that its effects can be accumulated during the echo time. The dendritic magnetic field has measurable effects on the MRI signal, but, it is necessary to differentiate the NMF effects from much bigger background BOLD effects to utilize the NMF effects for fMRI.

[1]  Bruno Maraviglia,et al.  Challenges for detection of neuronal currents by MRI. , 2006, Magnetic resonance imaging.

[2]  J. Xiong,et al.  Directly mapping magnetic field effects of neuronal activity by magnetic resonance imaging , 2003, Human brain mapping.

[3]  Ravi S. Menon,et al.  Intrinsic signal changes accompanying sensory stimulation: functional brain mapping with magnetic resonance imaging. , 1992, Proceedings of the National Academy of Sciences of the United States of America.

[4]  Soo Yeol Lee,et al.  Observation of the fast response of a magnetic resonance signal to neuronal activity: a snail ganglia study , 2006, Physiological measurement.

[5]  D. Plenz,et al.  Direct magnetic resonance detection of neuronal electrical activity , 2006, Proceedings of the National Academy of Sciences.

[6]  A. Song,et al.  Synchronized detection of minute electrical currents with MRI using Lorentz effect imaging. , 2006, Journal of magnetic resonance.

[7]  A. Destexhe,et al.  Dendritic Low-Threshold Calcium Currents in Thalamic Relay Cells , 1998, The Journal of Neuroscience.

[8]  Jeff H. Duyn,et al.  Hunting for neuronal currents: absence of rapid MRI signal changes during visual-evoked response , 2004, NeuroImage.

[9]  S. Kiebel,et al.  The MR detection of neuronal depolarization during 3-Hz spike-and-wave complexes in generalized epilepsy. , 2004, Magnetic Resonance Imaging.

[10]  Jia-Hong Gao,et al.  Direct MRI detection of neuronal magnetic fields in the brain: Theoretical modeling , 2006, NeuroImage.

[11]  R. Turner,et al.  Dynamic magnetic resonance imaging of human brain activity during primary sensory stimulation. , 1992, Proceedings of the National Academy of Sciences of the United States of America.

[12]  J. Bodurka,et al.  Toward direct mapping of neuronal activity: MRI detection of ultraweak, transient magnetic field changes , 2002 .

[13]  Steven W. Fleming,et al.  Further steps toward direct magnetic resonance (MR) imaging detection of neural action currents: Optimization of MR sensitivity to transient and weak currents in a conductor , 2006, Magnetic resonance in medicine.

[14]  J P Wikswo,et al.  The magnetic field of a single axon. A comparison of theory and experiment. , 1985, Biophysical journal.

[15]  A. Song,et al.  Lorentz effect imaging. , 2001, Magnetic resonance imaging.

[16]  R. Bowtell,et al.  Initial attempts at directly detecting alpha wave activity in the brain using MRI. , 2004, Magnetic resonance imaging.

[17]  R. Bowtell,et al.  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 , 2003, Magnetic resonance in medicine.

[18]  J. Bodurka,et al.  Current-induced magnetic resonance phase imaging. , 1999, Journal of magnetic resonance.

[19]  J. Bodurka,et al.  Direct detection of neuronal activity with MRI: Fantasy, possibility, or reality? , 2005 .

[20]  Leonid V. Kulik,et al.  Nuclear spin relaxation in free radicals as revealed in a stimulated electron spin echo experiment , 2005 .

[21]  R. Ilmoniemi,et al.  Magnetoencephalography-theory, instrumentation, and applications to noninvasive studies of the working human brain , 1993 .