Direct detection of the magnetic fields of neuronal impulses using MRI

The neuronal (ionic) current caused by nerve firing induces subtle and transient magnetic flux density changes that potentially modulate the MR signal over successive gradient echo planar image frames. Frequency spectra derived from Fourier transformation of experimental data down these time frames show evidence of a strobe stimulus localized to regions containing the optic nerve and visual cortex, which suggests that direct detection of the magnetic fields emanating from these regions has been achieved.