On the feasibility of neurocurrent imaging by low-field nuclear magnetic resonance

We describe a nuclear magnetic resonance (NMR) spectrometer operating at 20 mu T with a frequency resolution of 2 mHz to determine the intrinsic linewidth of the proton resonance in the human brain to be about 3 Hz. Using the same system we measured a biomagnetic field of 0.5 to 1 pT amplitude, which was generated by sustained brain activity evoked during repetitive median nerve stimulation. From these data, the effect of neuronal currents on the proton NMR signal was estimated. We conclude that neuronal currents may cause a measurable shift of the proton NMR line of brain tissue in low-fields. (C) 2010 American Institute of Physics. [doi:10.1063/1.3441410]